FIEST LESSONS 
 
 IN 
 
 SCIEFCB 
 
 BY THIS 
 
 RIGHT REV. JOHN WILLIAM COLENSO, D.D. 
 

 President White Ubrary, 
 Cornell University. 
 
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 First lessons in science 
 
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FIEST LESSONS IN SCIENCE. 
 
FIEST LESSONS 
 
 SCIENCE 
 
 DESIGNED 
 
 FOE THE USE OF CHILDKEN. 
 
 EIGHT EEV. JOHN WILLIAM COLENSO, D.D., 
 
 BISHOP OF NATAL 
 (1853—1883). 
 
 LONDON:' 
 WILLIAM EIDGWAT, 169, PICCADILLY, W. 
 
 1887. 
 
 Or 
 
^-4^ ^ 3 A ^2 > 
 
 c^,77^. 
 
 Af. 
 
ADVERTISEMENT. 
 
 Feom the author's Preface it will be seen that this little 
 ■work was drawn up for the use of a class of adult natives 
 of his diocese more than a quarter of a century ago. 
 It is scarcely necessary to say that during this interval 
 much progress has been made in Astronomical research, 
 in reference more especially to questions relating to the 
 distance of the Sun from the Earth, and to the probable 
 origin of the planetary system. The former is now 
 generally acknowledged to be somewhat less than it was 
 supposed to be ; and for the latter, some sort of hypothesis 
 of growth from a nebulous condition seems likely to win 
 its way to acceptance. But on neither point has any 
 definite determination been arrived at. It has been 
 thought best, therefore, to leave the figures as they were 
 set down by the author, one or two notes only being 
 added for the purpose of showing that they are not given 
 as the fimal expressions of facts not yet accurately ascer- 
 tained. So for the age of man on the earth, the author's 
 language must be taken only as affirming the compara- 
 tively late appearance of man in the world ; and this is a 
 fact which the geological knowledge of the present day 
 has not tended to call into question. This work is, 
 therefore, laid before the English public with full con- 
 fidence that its statements are supported by the latest 
 scientific conclusions of the day, and that the simplicity 
 and clearness with which the various subjects are treated 
 must render it especially useful in our national and 
 provincial schools. 
 
 George W. Cox. 
 
AUTHOR'S PREFACE. 
 
 These Lessons were originally written for tlie use of a 
 
 class of native adults, who were learning to read English. 
 
 It seemed desirable that they should be gaining some 
 
 information, as they read about the state of things around 
 
 them, instead of wasting their energies upon the child's 
 
 story of ' Dick Bell ' and his doings. I have accordingly 
 
 written the first portion of this little book in words of 
 
 one syllable. And I have endeavoured throughout to 
 
 avoid, as much as possible, such words and expressions, as 
 
 are likely to embarrass a reader of this kind. This part 
 
 is the first of a series, which will treat in order more fully 
 
 of Astronomy, Geology, &c., presenting such facts only as 
 
 ought to be known to every one. I have had to contend 
 
 with the difficulty of not being able to get suitable 
 
 engravings prepared in this colony. I may be able to 
 
 obtain them from England for a future edition. Mean- 
 
 •ftrhile I have done what I could, by means of simple 
 
 directions, to enable the Teacher to draw for the native 
 
 student such figures as he may need ; or he may be able 
 
 to find them already drawn, in elementary school-books. 
 
 Though originally planned, as I have said, for native 
 
 students, I trust this little \)o6k may be of use for 
 
 European children also. And I have, in fact, re- 
 
 Avritten the greater part of it, with a special view to their 
 
 necessities. 
 
 J. W. Natal. 
 
 BisHOPSTOWB, April 24, 1860. 
 
FIEST LESSONS IN SCIENCE. 
 
 1. The stape or form of the Earth on which, we live is 
 that of a great round ball, which we call a globe or sphere. 
 It does not seem to us at first to be so ; just as an ant, that 
 creeps on the face of a ball, would not see that it is round, 
 since it sees such a small part of it. Now we are like 
 ants, when we stand on the great globe of the Earth ; and 
 we can see but a small bit of its face at one time. And 
 so, if a man stood in the midst of a large plain, he might 
 think that the whole earth was flat, for it would seem so 
 to him, and he might say in his heart, " If I were to go on 
 and on for a long, long time, I might come to the end of the 
 earth at last, and what shall I do then ? " Or, if he was 
 one of a land where there are high hills and deep vales, he 
 might say, " It is not true that the earth is a globe, round on 
 all sides, as you tell me ; for how can this be, when here in 
 one place we go up to the top of some high hUl, and there 
 we go down, low down, to the bank of a stream ? " How 
 can it be that the Earth is a round globe, when there are 
 such hills and vales as these on its face, here and there, 
 on all sides of us ? 
 
 2. Yet the Earth is a round globe for all that. But 
 then it is a large globe, so large, that we need not think 
 much of all the hills and vales on the face of it when we 
 speak of the form or shape of the great Earth. So large 
 
2 FIEST LESSONS IN SCIENCE. 
 
 it is, that these hills are just like grains of fine dust on a 
 small ball, such as boys play with, and these vales are no 
 more to be thought of than the small pits which you may 
 see in the skin on the back of your hand, when you wish 
 to speak of the shape of your hand. This, which is here 
 drawn, will help you to see what I mean. The large space 
 is made to show the shape and size of the Earth ; and the 
 black line which goes round and bounds it is made to be 
 twice as thick as it ought to be, if we want to show, on 
 the same scale, the height of, those hiUs, which are known 
 to be the most high in all the Earth. All the high hills 
 and the deep vales, yes, and the deep, deep, sea, too, 
 would be no more than marks whieh we might make with 
 the least prick of a pin in that black line. So then we 
 might still say, that such a ball as this is round, though 
 we might scratch and mark it in this way, and then, of 
 course, its face would look rough to the eye, like the rind 
 of some kinds of fruit, and not smooth in all parts. And 
 so too we may say that the Earth is a round globe or 
 sphere, though it has on its face all these high hUls and 
 deep vales. 
 
 3. " But how is it known that the Earth is a rotind 
 globe like this ? Are there men who have gone all round 
 it and seen the whole of it and all its parts ? And did 
 they come back to their friends at home and tell them all 
 that they had seen ? Is that the way by which men have 
 come to know the shape and size of the earth?" No! 
 that is not the way. It is true that some men have gone 
 all round the globe, but not in all parts of it. And no 
 one man in the short time of his life could see more than 
 a small part of the face of the great Earth, let him do 
 what he can. But men do not need to go round the Earth 
 that so they may learn to know the shape and size of it. 
 There are ways by which wise men can come to know 
 
To face f age 1,. 
 
FIRST LESSONS IN SCIENCE. d 
 
 these things, and make quite sure that they know them ; 
 and yet they need not go round the world for this. I do 
 not say that all men can do this, I say that wise men can. 
 For a man must he wise by the gift of God, and he must 
 have read a great deal when young, and he must have 
 thought a great deal when grown up to be a man, that he 
 may have the skill to find out such things as these. But 
 when he has once found them out by his skill, he may 
 then teach us and all men to know them. 
 
 4. There have been such men, and there are such now 
 in the world. And in this way God shows His Love to 
 us, and helps us to know Him more and more, and to see 
 and feel how wise He is, and how great are His works. 
 He gives strength and skill to such men as these, that they 
 ■may read, and write, and think, and plod on, from day to 
 day and from year to year. And so they find out these 
 things, and a host of things like them ; and then they tell 
 us all that they have found out, and how they came to 
 find it out, and how they saw it to be true. And we too, 
 if we have some skill of our own by God's gift, though w© 
 may not have so much as they, may then see with our own 
 eyes — I mean, with the eyes of our minds — that these 
 things are just so as I have said ; we too may feel sure 
 that they have said the truth. In this way the Great 
 God, who made us and all things, shows to us here on 
 Earth, from time to time, more and more of his works, so 
 great and wise, and bright and good; and we learn to 
 bless His Name, and to bow our hearts to Him, as we 
 ought to do at all times, in fear and trust and love. 
 
 5, Now you who are so young as yet, and can but just 
 read a few small books, will not, of course, see all at once 
 the truth of that which these wise men have taught us. 
 But you can be made with ease to see that they have some 
 good ground for what they tell us, when they say that the 
 
 B 2 
 
4 FIRST LESSONS IN SCIENCE. 
 
 Earth is a great globe, if you will think of these things, 
 one by one, which I will now set down. 
 
 A ship can start from some one place in the Earth, and 
 sail on and on, and at last it wiU come right round once 
 more to the same place from which it set out at first. 
 This shows, at least, that the Earth is not spread out on 
 all sides, so as to be one vast plain, as some thought in the 
 old times which have long gone by. It proves that such 
 a ship has gone all round the globe, just as an ant or fly 
 may creep, if it will, all round a small ball, and come at 
 last to the same place once more from which it set out at 
 first. And it proves that the Earth must be a large globe 
 too. For it takes a ship a long time to go in this way all 
 round the globe. That is one thing which shows that the 
 Earth must be round in some way ; and now think of this 
 too, which I will tell you. 
 
 6. Let us stand on the shore of the sea on a fine clear 
 day, when things can be seen a long way off, and the wind 
 blows soft, and the face of the great deep is smooth. And 
 as we stand there, let us watch for a while the ships that 
 may sail by, or those that may sail to or from the land. 
 We shall soon have a proof that the sea is not quite flat, 
 as it may seem to us at first sight ; for we shall see that it 
 is bent down or curved in front of us, so as to hide from 
 our eyes the low parts of a ship which is a good way off. 
 Here then, in fact, we see with our own eyes the round 
 shape of the Earth ; for there are no hills and vales on the 
 face of the smooth sea, as there are upon the dry land, to 
 hide those parts of the ship from us. So that it is the 
 round form of the Earth, which, as a ship goes off from us, 
 on and on, out to sea, hides from our eyes more and more 
 of it, first the dark hull, and then the feet of the masts 
 and sails, and then their tops, till just the tips of them 
 are seen on the edge of the sea, and then these too are lost 
 
Tofacepcige 5. 
 
FIEST LESSONS IN SCIENCE. 5 
 
 to our sight ; and the whole ship is now quite hid from 
 our eyes by the round shape of the great Earth. 
 
 7. So too those who may sail in such a ship wiU see the 
 land seem to sink down more and more out of their sight 
 as they go off from it, and look back to take their last 
 view of it, till at last they can see it no more. When 
 they thus lose sight of it, it is not too far off for their eyes 
 to see it ; for, if a man will climb up to the top of the 
 ship's mast, he will see it still. But it is hid from those 
 who are down on the deck of the ship by the shape of the 
 Earth, which makes it swell or bulge out, as it were, in 
 the form of a curve, and so it shuts out the land from 
 their eyes. 
 
 You will see well how this takes place, if you look at 
 what is here drawn. This is a man who stands on a part 
 of the round Earth. And you will see that if we draw a 
 line A a from his eye, just so as to touch the globe at JB, 
 he will not see at all the low parts of the ship, which is 
 here drawn, for the bulge of the Earth's form hides them 
 from his sight. But he will see the tops of the masts and 
 sails, till at last, as the ship goes still on and on round 
 the globe, he will lose sight of those too. 
 
 8. It is just the same when a ship draws near to the 
 land. There may be those on board of it who have been 
 now, for a long while, far off from their homes, and whose 
 hearts long sore to see once more the dear old face of their 
 own bright land. And some of these, we may be sure, as 
 they walk the deck, hour by hour, to and fro, will take 
 their stand, now and then, on that side of the ship from 
 which they know the land will first be seen, and they will 
 fix their eyes on the line far off that marks, as it were, the 
 edge of the sea, and strain their sight, and gaze, in the 
 hope that they may catch a glimpse of the coast. At last, 
 they will see the tops of the high hills, that just peer up, 
 
6 riEST LESSONS IN SCIENCE. 
 
 as it were, from the sea in front of ttem j and then, as the 
 ship sails on, and draws near, and yet more near, to the 
 shore, they will see the woods and rooks, that reach down 
 to the brink of the sea, and the town, it may be, where 
 their own friends live, which lies, so calm and stiQ, in 
 the midst of them. 
 
 9. But now, if yon think of aU this which yoU have 
 read, you may say, " I see that these things do help to 
 show that the Earth is not flat — that its form is bent 
 and curved — that it must, in fact, in some way be round. 
 But how do they show that it is bent and curved, so as 
 just to take the form of a globe ? Why must it be round 
 in this way ? Why may it not have the form of an egg, 
 or be bent and curved in some strange way, so that its 
 shape may not be at all like that of a globe, which, we 
 know, is quite round, on all sides the same ? " 
 
 It is quite right that you should ask this. And now 
 I will try to help you to see how wise men have come to 
 know that the form of the Earth is not like that of an 
 egg, — that it must be round like that of a globe or sphere. 
 If a man stands on the deck of a ship that is far out at 
 sea, far off from the land, he will see, of course, no more 
 than the sea and the sky. And, if the day be fine, and 
 the sky clear, when the wind blows soft, and the waves 
 do not toss or swell, he wiU see the face of the great deep 
 spread out on all sides smooth and still, and he will see 
 too the line which ends it, as it were — which hems it in 
 and bounds it all round, and seems to part it from the 
 sky, — ^bent so as to make a curve all round him. His own 
 feet will be seen to stand just in the mid point of that 
 curve, so that each point of that whole line will seem to 
 be as far off from him as one of them is. Such a curve 
 as this we call a cir-cle, and the mid point of it we call its 
 Cen-tre. And so you will know this fact, and you must 
 
FIRST LESSONS IN SCIENCE, 7 
 
 try to bear it in mind, tliat if lines be drawn, like the 
 spokes of a wheel, from the centre of a circle to meet the 
 line which bounds it, they will all be of the same length. 
 And so too it is with a sphere or globe ; if lines be drawn 
 from its mid point or centre, to meet the face of it, which 
 is called its sur-face, they will all be of the same length. 
 
 10. Well! let us go back now to speak of the man, 
 whom we left in the ship. It may be that, as he looks, he 
 will see the tops of a ship's masts and sails, which just 
 peer up, and seem to come up out of the sea as it were, far 
 off on its edge, on that line or circle which goes all round 
 him, and parts the sea and the sky on all sides of him. 
 And, as he still looks on, the masts and sails will come up 
 more and more, till, at last, he will see, the whole of them, 
 and then the dark hull of the ship, low down in the sea. 
 This ship is, in fact, a ship like his own, which is on its 
 way to some port, and has been hid from his sight till 
 now by the bulge of the Earth's round form. At last it 
 has come near to his own ship, so near that it can be seen. 
 Soon it will come close to him and pass him, and then it 
 will sail on and on, till he will once more lose sight of it, 
 first of the hull, then of the feet of the masts and sails, 
 and then of their tops. This will be when it gets so far 
 off from him, as to cross once more that line or circle, 
 which seems to his eyes to part the sea and the sky. And 
 lie same thing will be true, if the man sails on in the 
 ship from place to place. He will still see such a line as 
 this, a circle, of which the place where his own feet stand 
 is the centre, that will seem to part the sea and the sky, 
 and bound the range of his sight on the wide sea. And if 
 he goes up to the top of the ship's mast it will be stUl 
 the same ; though the circle will not be quite so small as 
 when he stood low down on the deck. 
 
 11. Mark this well then! In all parts of the sea, as 
 
8 FIRST LESSONS IN SCIENCE. 
 
 seen by the eyes of this man, tlie line whioli TDOiinds the 
 sea and the sky will he a circle. 
 
 Now those wise men, of whom I told you, take note of 
 this; and they know by this fact that the form of the 
 Earth, in all parts of the sea, must be that of a globe or 
 sphere. They know that this is the case by proofs which 
 they can give; but these proofs would not be plain to 
 those who are so young as you are. But they are sure of 
 this, that the face of the great deep must take the form of 
 a sphere or globe, if this fact be true, as they find it is, 
 that a man who stands in a ship, in this or that part of 
 the sea, sees the line, which bounds the sea and the sky, 
 take no form round him but that of a circle, of which the 
 place of his own feet is the centre. And they can do more 
 than this. For by the size of such a circle, as seen from 
 the deck of a ship, they can judge of the size of the great 
 globe too. And they can show that it must be so large 
 that, as you were told at first, the high hills and deep 
 vales, which, we know, are found on the face of the land, 
 must be thought of but as small things, mere specks and 
 grooves, not worth our while to speak of, when we bear 
 in mind the huge bulk of the whole Earth, and speak of 
 its shape. 
 
 12. If a man were to get up on the top of a high hill, 
 in the midst of a wide plain, here too he would see the 
 same kind of curved line, or circle, run round him, as it 
 were, and bound his sight on all sides. Of course it would 
 not be so in a land full of hills and dales, and where ups 
 and downs of all kinds break up, here and there, the face 
 of the ground. But if he could mount like a bird that 
 soars up on high, so as to get far off from the Earth, he 
 would then see much more of its form than he could from 
 the top of a hill. He would not now see so much of the 
 hills and vales. They would soon get to look small, as he 
 
FIEST LESSONS IN SCIENCE. 9 
 
 went up and up. And he would see the ground spread 
 out like a vast plain at his feet, with dark spots where 
 the towns and woods are, bright streaks where the streams 
 are, and a scratch or rough place, here and there, which 
 marks a ridge of hills. There would be a line too, now 
 quite a large wide circle, though it will not seem so large 
 as it did, which would hem. in his view, and bound what 
 he can see as yet of the Earth's great face. And this too 
 would be the same in all parts of the Earth. So that wise 
 men can show, by means of this fact, that on the dry land 
 too, as well as on the sea, the form of the Earth is round 
 like that of a globe. 
 
 13. This must do for you now at this time on this 
 point. One day I hope to tell you more. But now you 
 must see that there is good ground for what these wise 
 men say, and you must take their word for what they see 
 to be true, though it is more than what you can see with 
 your own eyes. 
 
 So then, if the man we spoke of could rise on still, high 
 up in the sky — up, up, where no bird could fly, and no 
 man could live — he might at last look down, and would 
 see the whole earth, like a great ball hung in the sky, 
 just as we can now look up and see the Sun and the 
 Moon. 
 
 " But how can this be ? If the Earth be a great ball 
 like this, how can it be hung up there in the sky? In 
 what way is it hung ? What does it hang by ? " 
 
 Tou may well ask this ; and I wiQ ask you too to tell 
 me how the Sun or Moon is hung up in the sky. And yet 
 we see that they are hung there, though we do not see in 
 what way they are hung, or what they hang by. So then 
 we need not think it strange if these wise men say that 
 the Earth too is a great globe, which hangs in the sky, 
 like the Sun or the Moon — which hangs free in its place, 
 
10 FIRST LESSONS IN SCIENCE. 
 
 just as they do, and is not held Up at all or kept fast by 
 props or bands. 
 
 14. But still you may say, " The Earth is so large, and 
 the Sun and Moon are small. It seems strange that those 
 small bright balls should stand up there in the sky and 
 not fall. But it is still more strange that a ball so huge 
 as the great globe on which we live should hang in this 
 way in mid air just as they do." 
 
 Then I must tell you that the Sun and Moon are not 
 small as you think, though they may seem to be so. But 
 they are a great way off from us. And it is that which 
 makes them look so small in our eyes ; just as a bird 
 which you know to be a large one will look like a mere 
 small speck when you see it far up in the sky. I shall 
 hope to tell you one day how large the Sun and Moon 
 both are, and how far off they are from the Earth. But 
 now I will just say this. The Moon is a great baU too, 
 like the Earth, but not so large as the earth by a great 
 deal. And the Sun is a great ball too, but so large and 
 huge, that it will be hard to show you, so as to make you 
 see and know, and feel, as it were, with the hands of your 
 mind, how large it is. But this you must bear in mind 
 from this time forth, that the Sun is a huge globe, and 
 far more large than the Earth. In fact, if we were to 
 take the head of a pin to show the size or bulk of the 
 Earth, then the head of a man would show much on the 
 same scale the bulk of the Sun. 
 
 15. And what is yet more strange and grand for you to 
 think of, each one of those bright specks which we see 
 Tip in the sky at night, and which we call the Stars (if we 
 leave out a few of them), is quite as large and bright as 
 the Sun, and some of them are much more so, though all 
 are so far off that they look as mere points of light. More 
 still than this you may be told. You may see here and 
 
FIEST LESSONS IN SCIENCE, 11 
 
 there in the sky on a fine clear night, small clouds of 
 light, not bright as the light of the stars, but more faint. 
 And there is a long trail too of light, drawn through a 
 large part of the sty, which must, I think, have caught 
 your eye now and then, though you may not have marked 
 as yet those same small clouds which I spoke of. Now 
 all the light in this long trail and in those small clouds, 
 comes from a host of stars, which are so far off that they 
 look like mere fine dust, if, in fact, they can be seen by 
 the eye at all. But each one of them is a Sun, a great 
 Sun like ours, a huge bright globe, as bright and grand 
 as that which we see, and which we call our own — as 
 bright as that Sun, which God, our God, has made for us, 
 to cheer our eyes and hearts, to bless our whole life, and, 
 more than all this, to be a sign to us of His Great Love. 
 
 How great and good is God ! Let Heaven and Earth 
 praise Him, and all the hosts that are in them, the hosts 
 which He has made by the Word of His Mouth. " Praise 
 ye Him, Sun and Moon ! Praise Him, all ye Stars of 
 Light ! all things that have breath and life, praise ye 
 the Lord ! Praise thou the Lord, O my soul ! " 
 
 16. I will now go on to tell you more about this Earth, 
 on which we live. It is, as you have heard, a very large 
 ball. And you know also some of the reasons, which 
 have led men to say this, and to be quite sure about it, 
 though they have not been able to travel over all parts of 
 the Earth, or to mount up into the sky so high as to see 
 plainly the form of it. There are other reasons still 
 stronger than those which I have told you ; but you are 
 not yet able to be taught about them, though I hope some 
 day you will be. 
 
12 FIRST LESSONS IN SCIENCE. 
 
 Well then ! if the form of the Earth is that of a large 
 ball, the next thing we should like to know is, " How large 
 is that hall 2 What is the size of it ? Are wise men able 
 to tell us all about this ? " 
 
 Yes ! if they are sure that the Earth is a globe or 
 sphere, they know also that they need only measure, that 
 is, find the length of, a short line upon its face, in order 
 to know the length of a line which goes right through 
 the centre of the globe, from one side to the other, and 
 also the length of a line which goes all round the globe, 
 so that a man might go along it, starting from any one 
 place, and go on and on, until, at last, having gone quite 
 round the globe, he would come to the very same place 
 again. I should like to make you see a little how this is 
 to be done —I mean, how we can find out the lengths of 
 each .of these lines, when we know the length of one short 
 line upon the face of the globe. But this would be too 
 hard for you at present. So it will be enough for me to 
 tell you what these wise men have found out for us, 
 without teaching you just now the way in which they 
 have found it out. 
 
 17. But, first, I must explain to you the meaning of one 
 or two words, which are much used in speaking of such 
 matters as these. You know a little by this time what is 
 meant by a circle and a sphere, and you know also what is 
 meant by the centre of a circle or sphere. You know that 
 the outer face of a sphere or globe is called its surface ; 
 and so too the line, which goes round a circle, and bounds 
 it in on all sides, is called its circumference. This long 
 word is taken out of the Latin language, which was 
 spoken by the famous old people of ancient Eome, and it 
 means a line which carries all round. 
 
 But now let me tell you more plainly, that a circle is a 
 flat figure, or, as it is called, a plane figure, such as may 
 
FIEST LESSONS IN SCIENCE, 13 
 
 be drawn on one side of a flat piece of paper ; so that it 
 cannot lie taken off tiie paper, for it has only length and 
 breadth, and no thickness. You may cut out a piece of 
 paper, which shall have the form of a circle, that is, you 
 may cut out a circular piece of paper ; but, strictly speak- 
 ing, yon cannot cut out a circle ; it only lies on one side 
 of the paper. And a circle is bounded by one curved line 
 which is called its circumference, and whose nature is 
 such, that all straight lines drawn from the mid point, or 
 centre, of the circle to meet the circumference, are equal 
 in length. Now any such straight line as this is called a 
 radius, that is, a ray or spoke, of the circle, like the spoke 
 of a wheel of a wagon. This word, radius, is also a word 
 of the Latin, language : and when we have to speak of 
 more such lines than one, we must change the word again 
 by the rules of the Latin language, and call them radii of 
 the circle. 
 
 18. So then, a line drawn from the centre of a circle to 
 the circumference, or from the circumference to the centre, 
 is a radius of the circle. And a line, which is drawn 
 right across the circle, through the centre, to meet the 
 circumference at both ends, is called a diameter of the 
 circle, from a word of the old Greek people, which means 
 a line that measures right through. It is plain that the 
 diameter of a circle divides the circle into two equal parts, 
 and that the length of a diameter is twice that of a radius. 
 You cannot see at once in the same way what is the 
 length of the circumference. But it has been found out 
 that the length of the circumference is rather more (about 
 one seventh more) than three times the diameter, which is 
 the same, of course, as six times the radius. 
 
 All figures, which can be drawn, like a circle, on one 
 side of a flat piece of paper, and which have, therefore, 
 only length and breadth, but no thickness, are called plane 
 
14 FIRST LESSONS IN SCIENCE. 
 
 figures. Those wHch. have length and breadth and 
 thickness are called solid figures. Hence a sphere or 
 globe is a solid figure. And a sphere too has its centre, 
 and radii, and diameters; and the radii are all equal, 
 drawn from the centre to the surface ; and the diameters 
 are all equal, drawn right through the centre of the 
 sphere, to meet the surface at both ends; and each 
 diameter is the double of any one of the radii. 
 
 19. Well ! the radius of the great sphere or globe of 
 the Earth is found to be about four thousand (4000) 
 . miles, and, therefore, its diameter is about eight thousand 
 (8000) miles ; and its circumference, which, you know, is 
 rather more than three times the diameter, is about 
 twenty-five thousand (25,000) miles. Tou will now be 
 able to form some better notion of the size of the Earth. 
 For instance, we know that a strong man, who can walk 
 well, can manage to walk about fifty (50) miles in one 
 day, if he walks all day long and rests at night. Now 
 suppose that such a man could walk on in this way, day 
 after day, month after month, without stopping. It 
 would take him just five hundred (500) days, or more than 
 one whole year and four months, to go round the Earth. 
 Again, suppose that a hole were bored right under your 
 feet, down, down, through the centre of the Earth and 
 past it, till it came out to the light again on the other 
 side. And suppose that a man were able to go down that 
 hole at the same rate of fifty miles a day. At the end 
 of eighty (80) days he would reach the Earth's centre. 
 And at the end of eighty (80) days more he would come 
 out on the other side. So that it would take him one 
 hundred and sixty (160) days, or more than five months, 
 to go right through the Earth, along one of its diameters, 
 and come out among the people, who live on the other 
 side. 
 
FIEST LESSONS IN SCIENCE. 15 
 
 20. " But are there people," you may ask, " who live 
 down there, below our very feet, on. the other side of the 
 earth ? " Yes ! indeed there are, and a great many people 
 too, and just such people as we are ; though, perhaps, the 
 colour of their skin may be not quite the same as ours. 
 " But who knows this ? Has any one seen these people ? 
 Has any one talked with them ? " Yes ! sailors, and other 
 persons, who have gone round the world in ships, have 
 seen these people, and talked with them, and then have 
 tx)me back to tell the story of them. " But can we see 
 them with our own eyes, these people, who live on the 
 other side of the Earth?" No! not unless you go to 
 them across the sea, or unless they come across the sea to 
 you. For a man cannot really go all round the Earth, 
 walking on foot all the while, as we supposed ; because 
 there are oceans, that is, great seas, which must be crossed 
 in some parts, before he could get from the place where he 
 lives right round to the other side of the Earth, and see 
 the people who are living there. " But these people, do 
 their heads point up to the sky, and their feet stand upon 
 the ground, as ours do ? " Yes ! God has made man alone, 
 of all the creatures upon the Earth, to stand and walk 
 with an upright body, as we do. And they too are men, 
 and walk with their heads upwards, and their feet tread- 
 ing on the ground, just as we do. " But then their feet 
 must be pointed up to ours, and their heads must be 
 hanging downwards. How can they stand or walk, or 
 live at all in this way ? " 
 
 21. Listen, and I will tell you. Look at this book, 
 which I let fall from my hand. It falls at once to the 
 ground; and why? You will say, because it is heavy. 
 But why is it heavy ? What makes it to have weight at 
 all, and to fall with such force upon the ground ? And all 
 othra' things, which have weight like this, how is it that 
 
16 FIRST LESSONS IN SCIENCE. 
 
 they are heavy ? What makes them all fall down at once 
 to the ground, if we let them go? A man, when he 
 jumps, why does he feel it to be so hard to jump up, and 
 so easy to jump down ? And, when he leans too much on 
 one side, or forward, or backward, what makes him feel 
 that he cannot keep himself any longer up upon his legs, 
 than he must topple over, and fall down upon the ground ? 
 
 In all these oases, it is the Earth itself which draws 
 things to itself — the Earth with its huge bulk and its 
 great mass. It is the Earth which pulls down the book 
 and the man's body to itself. It tries to draw all things 
 down to its own centre. This is why you feel a pain in 
 your neck after leaning, forward a long time to write. 
 The Earth has been pulling your head down to itself; but 
 you have all the while been holding it up by means of the 
 muscles of your neck, without knowing what you were 
 doing, simply because you willed it. And now those 
 muscles are tired, and you feel pain, and you lift up your 
 head for a time, that you may give them rest. So again, 
 if you fall asleep while sitting, your head will fall 
 forward, like a heavy weight, upon your breast, because 
 in your sleep you are no longer able to act by your will, 
 and to make your muscles do their duty, arid hold it up. 
 
 22. So then this is why we are able to stand upright 
 upon our feet without fear of falling, because the Earth 
 has the power, which Grod has given it, of drawing our 
 whole body right down upon our feet, so that it presses 
 on them and rests upon them. But, if a man leans over 
 too much on one side, then the Earth will draw that part 
 of his body, which hangs over his feet, so strongly right 
 downward, that he will not be able with the muscles of 
 his legs to resist its power, and so his body must come to 
 the ground, that is, it must fall. 
 
 You may see, indeed, a fly walk up a wall, or even 
 
FIRST LESSONS IN SCIENCE. 17 
 
 along the ceiling of a room, with its feet upwards and its 
 body hanging downwards, and yet it will not fall. But 
 this is because God's Wisdom has made its feet in a 
 strange way, which one day I hope to explain to you, so 
 that it is able to hold on thus, and to stick to the wall or 
 ceiling, although it is still pulled downwards by the 
 Earth, as all things else are. 
 
 And the same thing takes place on the other side of the 
 globe. The Earth there too draws all things down to 
 itself, and tries to get them to its own centre. A book, if 
 let go from the hand, will fall there, as here, down to the 
 ground towards the Earth's centre. A man will stand 
 upright upon his feet there, as here, because the Earth 
 draws down his body, so as to make it press his feet upon 
 the Earth, unless he leans too much on one side, and then, 
 as before, the Earth wUl draw down to itself that part of 
 his body, which hangs over his feet, and he too must faU, 
 if the muscles of his legs are not able to resist its power. 
 
 23. You will now see that the words " up " and " down " 
 must always be thought of with respect to the person 
 who uses them. " Up " is always up above a man's head, 
 and " down " is always down below his feet, which will 
 point towards the Earth's centre, let him live where he 
 may. And so there are people, as I have told you, who 
 live on the other side of the Earth, and whose feet point 
 to ours, and who are, therefore, called our Antipodes, from 
 a Greek word which means people whose " feet point to 
 ours." And their heads are upward and their feet 
 downward, though their "up" is not the same as our 
 " up," and their " down " is not the same as our " down." 
 And so too those people, who live in other parts of 
 the Earth, will call it up, when they point up over 
 their heads, and down when they point down under their 
 feet. 
 
 c 
 
18 FIRST LESSONS IN SCIENCE. 
 
 24. When, therefore, we point tip to Heaven, and say 
 that God is there, and when we pray, and say, '' Our 
 Father, which art in HeaTen," we do this, not because we 
 think that He lives up above our heads, any more than 
 that He lives down below our feet. But we use such 
 words as these because it is the way of men to speak of 
 all things, that are very great and glorious, as being high 
 above their heads, in a place which they cannot attain 
 unto, and because we are to think of our Father's Glory 
 and Greatness as higher than all our thoughts can reach, 
 though they soar upwards sometimes, like a bird, as it 
 were, to find Him. 
 
 But those on the other side of the globe, and all other 
 people too in all parts of the Earth, they too may look up 
 to the Heaven above their heads, and say, " Our God and 
 Father is there ! " though they will not be pointing to the 
 same region of the sky as we do. For God is high above 
 the reach of their minds also in His Glory and Greatness, 
 ay, and in His Goodness also. " As the Heaven is high 
 above the Earth, so great is His Mercy toward them that 
 fear Him." 
 
 25. But God is not only above our heads, and above 
 their heads. He is present with us in every place — high 
 above in the Heavens, to behold and govern all things — 
 but near to us here upon Earth, near, very near, to us 
 His children, in the very centre of our being, to comfort 
 and bless, as well as to correct and chasten, to teach us by 
 His Spirit, to guide us by His Counsel here, that He may 
 bring us to His Glory. As the Psalmist David wrote of 
 old, " Lord, Thou has searched me out and known me ! 
 Thou art about my path, and about my bed, and spiest 
 out all my ways. Thou hast beset me behind and before, 
 and laid Thine Hand upon me. Such knowledge is too 
 wonderful for me; it is high, I cannot attain unto it. 
 
FIRST LESSONS IN SCIENCE. 19 
 
 Whither shall I go from Thy Spirit ? or whither shall I 
 flee from Thy Presence ? If I climb up to Heaven, Thon 
 art there ; if I go down to Hell, Thou art there also. 
 Search me, God, and know my heart ; try me, and know 
 my thoughts ; and see if there be any wicked way in me, 
 and lead me in the way everlasting." 
 
 26. But now you will, perhaps, be asking, " What is it 
 that makes the Earth draw to itself all other things in 
 this way ? " No one but God Himself, the Mighty Maker, 
 knows the whole reason of this. Yet I will tell you 
 something more about it, as far as he has given us power 
 to look into the Wisdom of His Work. 
 
 But, first, you must learn to know the proper meaning 
 of those two words, bulk and mass, which I used a little 
 while ago. When we speak of the hulk of a thing, we mean 
 its size ; but then it must be something which has length, 
 breadth, and thickness. We can speak of the bulk of a 
 tree or a mountain ; but we cannot speak of the bulk of a 
 line or circle ; we must say the length of a line, and the 
 size of a circle. Again, when we speak of the mass of a 
 thing, we mean the amount which it has in it of that 
 which is called matter. Now matter is the name given to 
 the substance or stuff of any kind, which makes up a hody ; 
 and a body is anything that can be touched, or that takes 
 up room for itself in space. Thus vfood, of which a log 
 or a table is made, is one kind of matter ; and water, of 
 which the sea or a river is made, is also a kind of matter, 
 and flesh, and bone, and blood, these are some of the 
 matters, of which our bodies are made ; and the substance, 
 of which each one of these is made, would be called the 
 matter of flesh, and the matter of bone, and the matter of 
 blood. I repeat then, any thing is called matter which 
 makes up any body. And the mass of a body is the whole 
 amount of matter of any kind which it contains. And a 
 
 c 2 
 
20 FIRST LESSONS IN SCIENCE. 
 
 particle of matter is the very smallest portion we can con- 
 ceive of the matter, which makes up any body. 
 
 27. Now God has given to each particle of matter of 
 any kind a power to draw to itself, or attract, every other 
 particle, with a force which is stronger as the particles are 
 nearer, one to the other. This power is very small, when 
 we think of only one minute particle, which attracts a 
 second minute particle, unless they are very close indeed 
 the one to the other. But, when a vast number of parti- 
 cles are joined to make one body, and a vast number of 
 bodies are joined to make one great mass, then the power, 
 which this whole mass of matter exerts on any particle, 
 if it be not too far off, may be very great. 
 
 Now the Earth is just such a huge mass of matter, 
 made up of a vast number of bodies of all kinds of matter. 
 On the surface we see the hills and mountains, made of 
 hard rooks, and the vast seas and oceans, made of water; 
 and under the bottom of the mountains, and under the 
 bed of the sea, and under the plains and wide-spread 
 regions of the Earth, is matter of some kind or other, 
 reaching down, as we have reason to believe, to the very 
 centre. The whole Earth then, throughout its huge 
 bulk, is one great mass of matter. And this mass must 
 attract, or draw to itself, each particle of matter, in any 
 other body, not too far off from it, with a very great force ; 
 and thus it will make the body seem to be heavy, will 
 make it have weight. Each particle of matter in a man's 
 body is thus drawn down by the whole mass of the Earth. 
 And each particle of matter in the Earth is in like manner 
 drawn upwards by the whole mass of the man's body. But 
 the huge Earth pulls with a mighty force, and the man's 
 small body with a very, very, small one, which it is not 
 worth while to speak of at all, so very small it is, when 
 we think of the mighty pull of the Earth's great mass. 
 
FIRST LESSONS IN SCIENCE. 21 
 
 28. " But what is known about the inside of the Earth? 
 Can wise men tell us anything about the matter of all 
 kinds which fills up its huge bulk ? " Yes ! indeed they 
 can ; they have learned a great deal about it, and yet very 
 little, when we come to look at the vast thickness of the 
 great globe. They are able to tell us much about that 
 which we call the crust, or outside, of the Earth, to the 
 depth of about eight, or perhaps, ten miles from the sur- 
 face. But what is that to the Earth's radius, the distance 
 from the surface to the centre, which we know to be four 
 thousand (4000) miles ? You will see, if you will' draw a 
 figure like that which you first looked at (p. 2), that is, if 
 you will draw a circle, such that the length of the radius 
 shall be 400 times the thickness of the bounding line or 
 circumference. Eor the circle in that figure is meant, as 
 you know, to set forth the great globe of the Earth, and 
 the bounding line is niade twice as thick as it ought to be, 
 to set forth, on the same scale, the height of the highest 
 mountains, which is about five miles. Hence this line 
 sets forth a thickness of ten miles, that is, it sets forth to 
 us the thickness of the Earth's crust, so far as we are able 
 to search into it, and know any thing for certain about it. 
 In fact, if we take a fowl's egg to show the size of the 
 Earth itself, the shell will be much too thick to show on 
 the same scale the thickness of this crust. 
 
 29. But still there is a great deal that may be told you 
 about this same thin crust. By searching into it with 
 great care, using the powers of mind which the Blessed 
 God has given them, learned men have come at last to 
 make the Earth tell, as it were, its own strange story to 
 us. It is written in the rocks which lie beneath our feet. 
 There we may learn to know not only what the outer 
 crust of the earth is made of, but how it was made, what 
 changes have passed over it in ages long gone by, what 
 
22 FIRST LESSONS IN SCIENCE, 
 
 plants and trees and living creatures, what beasts and 
 birds and reptiles and fishes, what trees and plants with- 
 out number, have lived and died upon it, long, long before 
 there was a man to till the ground, to see the Glory, and 
 taste the Goodness, and show forth the Praises of God. 
 All knowledge of any kind such as this, which wise men 
 have gained, is called Science; and such men are called 
 men of science, or scientific men, or sometimes, philosophers, 
 from a Greek word, which means "lovers of wisdom." 
 And that part or branch of science which tells about the 
 Earth's crust, and the matter of which it is made, is called 
 Geology, from a Greek word again, which means " discourse " 
 (or talk) « about the Earth." 
 
 30. Now we all know that there are found near the 
 Earth's surface stones and rooks of many kinds and 
 colours, which are seen here and there, sometimes in great 
 masses, making hills and lofty mountains, sometimes in 
 the beds of streams or on the banks of rivers — sometimes 
 in quarries, that is, places where stones are dug out, with 
 which houses are built, or in cuttings, that is, places where 
 a wide road is made right through a hill — sometimes again 
 as they come out to view a little, or, as it is said, crop out, 
 on the side of a hill, perhaps in the very middle of a bed 
 of grass. There is limestone, which is burnt to make the 
 white lime for mortar and whitewash, and slate, with 
 which the roofs of houses are often covered, and the black 
 coal which is used for fires, and other stone which serves 
 for building. There is soft clay, of which bricks are 
 made, and loose sand, and hard granite. 
 
 31. Now we might have thought, as, indeed, for a very 
 long time men did think, that all these remain now just 
 in the same state as when they first were made. We 
 know, indeed, that a river will sometimes come down, 
 swelled by heavy rains or by the melting of snow, in a 
 
FIEST LESSONS IN SCIENdE. 23 
 
 miglity roaring flood, and flow over its banks on all sides. 
 When the flood has passed away, we may fiiid, perhaps 
 that the stream has changed its course, and that places are 
 now buried up under stones and sand, where the grass 
 once grew, while others are covered with a thick layer of 
 mud, or a large sheet of water. Perhaps, in that mud 
 may be hid up also dead bodies of drowned beasts, or birds, 
 or snakes, or, it may be, of people. Many shells may be 
 buried in it ; and such shells, or the bones of these crea- 
 tures, may be dug up at some future day, and show the 
 people of that time what a flood there had been, and how 
 many living things had been destroyed by it. But still, 
 we should say, such places as these must form but a very 
 small portion of the Earth's great surface. That must 
 remain, upon the whole, much in the same state as when 
 the Word of their Mighty Maker called all these things 
 forth into being. 
 
 32. But, in truth, it is not so. A very little searching 
 into the matter is enough to show that this is very far 
 from being the case. The face of the whole Earth has 
 been changed again and again, as time passed on. Some- 
 times a great extent of land has been raised above the 
 waters in a very short time by the dreadful throb of an 
 earthquake ; sometimes it has been very slowly lifted from 
 beneath by the quiet steady working of some mighty 
 power. Sometimes, again, vast regions of dry land have 
 sunk down in a moment, or have sunk down slowly — a 
 few feet only it may be, in a hundred years — and been 
 buried deep at last beneath the ocean. Many of the rocks 
 which we now behold were formed, not in a moment, when 
 the Earth itself was made, but by degrees. The matter, 
 of which their substance is made, has been dropped down 
 through the course of long, long ages, in the form of mud 
 or sand, or gravel, at the mouth of a great river, or at the 
 
24 FIRST LESiSONS IN SCIENCE. 
 
 bottom of a sea. There it was pressed down by the heavy 
 weight of other matter, and the deep sea itself lying oyer 
 it, and so, at last, it came to be a hard firm rock as now 
 we see it. Others have been formed by matter which has 
 been poured out at first like molten iron, red-hot, from the 
 very bowels of the Earth, through holes which it found, 
 or which it made for itself, with furious force, in the thin 
 crust ; and these by degrees have cooled down, till they 
 too become solid masses of hard rock, as we now behold 
 them. And here and there, in all parts of the Earth, are 
 found buried deep in many of these rocks — though not, of 
 course, in those that have been formed of melted matter — 
 remains of living creatures of all kinds that have lived 
 and died, and passed away in former ages, long before 
 man was placed upon the Earth, many of them strange 
 and uncouth in form, and very few of them of kinds like 
 those that are now living upon the Earth. 
 
 33. This explains roughly what we know of the way in 
 which the Earth's crust was formed. But now I must go 
 on to tell you a little more about all this. It is very likely 
 that, when the Earth was first brought into its present 
 shape, it was wholly formed of red-hot molten matter. 
 Philosophers have good reason for saying this, as you will 
 see for yourselves more plainly as we go on. But then 
 you will, perhaps, be asking, " Had this liquid matter, of 
 which the Earth was made, the same round form of a 
 globe which the Earth has now ? " Yes ! Strange as it 
 may seem at first to say it, yet this red-hot molten matter 
 took the very same form which the Earth has now, and 
 which it has kept from that time to this. But here I 
 must tell you that that form is not quite that of a sphere, 
 as we have all along been saying, of which all the diameters 
 you know, are equal. Yet it is almost that of a sphere, 
 and differs so very little from it, that in our common talk 
 
FIEST LESSONS IN SCIENCE. 25 
 
 we may speak of it as a sphere, having all its diameters 
 of the same length, about 8000 miles. Still the true 
 shape of the Earth is more like that of an orange ; that is, 
 it has the form of a sphere that has been pressed in a 
 little or flattened at the two ends of one of its diameters, 
 so that that diameter, which is called the axis, is shorter 
 than any other. Midway between the two ends, or jpoles, 
 as they are called, of this axis, the shape of the Earth, of 
 course, bulges out a very little all round. And the curved 
 line which goes round the globe in this middle part, where 
 it bulges out, and which is, in fact, the circumference of a 
 circle, is called the Equator, from a Latin word, which 
 means the line "that makes equal," because it plainly 
 divides the whole surface of the globe into two equal 
 parts. 
 
 34. Now it has been found out by the skill of philo- 
 sophers that the Earth's axis, or polar diameter, is just 
 shorter by twenty-six miles than any of its long Equatorial 
 diameters — that is, than any line which may be drawn 
 right through the Earth's centre, from any point in the 
 Equator, so as to come out at a point on the other side of 
 the globe. In fact, the exact length of any one of the 
 longer diameters is found to be 7924 miles, and that of 
 the shorter diameter, or polar axis, is found to be 7898 
 miles. But they are both so very large that the small 
 length by which the one exceeds the other would hardly 
 be noticed at all by the eye. If a man were looking upon 
 the great ball from some place in the sky a long way off, 
 it would seem to his eyes to have the true form of a perfect 
 sphere. 
 
 35. Now you will not forget what you have been told 
 about the power which God has given to every particle of 
 matter, to draw to itself, or attract, all other particles. 
 Hence, if the Earth was made at first of fluid matter, each 
 
26 FIEST LESSONS IN SCIENCE. 
 
 particle of this matter would attract all the rest. And 
 philosophers have shown that such a mass, if left to itself, 
 would settle down, hy reason of this attraction, into the 
 form of a perfect sphere. But they have shown also that, 
 if this same fluid mass has a whirling motion given to it, 
 so as to spin round like a top, about a line through its 
 centre or central axis, it will lose the form of a perfect 
 sphere, and take that of a sphere that is pressed in, or 
 flattened, at the poles, and bulges out at the Equator, mid- 
 way between them. The faster it whirls round, the more 
 it will be pressed in at the poles, and bulge out at the 
 Equator. And, if they know the exact rate at which it 
 whirls, and the length of either the longer or the shorter 
 diameter, they are able to find out for themselves what 
 must be the length of the other. I mean, they are able 
 by their skill to reason it out on paper, and tell us by how 
 much the one must be longer than the other, without 
 having any need to measure it. 
 
 36. Now the fact is that the great Earth, upon which 
 we are placed, does turn round thus upon its axis once in 
 twenty-four hours. Each day that we live, the huge 
 globe is spinning round in this way, with all the people, 
 and other creatures, that live upon it. You may ask, 
 " Why do we not feel that we are moving, if this is the 
 case ? " And then I might answer, " Do you think that a 
 very small fly, perched upon a large waggon, would feel 
 that it was moving, if the waggon were turned round 
 with smooth steady motion, so as not to shake or jerk it ? " 
 And we men are very small flies indeed, smaller than the 
 smallest we can think of, if we compare our size with that 
 of the huge Earth. And so we go around with it as it 
 turns with a smooth steady motion, without any jerk or 
 shaking; and we are not at all conscious that we are 
 moving by anything that we can feel, though, as I shall 
 
FIRST LESSONS IN SCIENCE. 27 
 
 show you iDefore we go much further, we are indeed 
 moving at a very rapid rate. But though we cannot /eeZ 
 this motion of the Earth, turning round, day by day, upon 
 its axis, because we are all going round so smoothly with 
 it, yet we may know that we do so by something which 
 'we see daily; for we are not flies, that have no reason 
 given them to take account of such things. 
 
 37. We see, then, the Sun, day by day, rising, as it seems, 
 in the East, and moving on and on, till he gets high up 
 over our heads, and then dipping down again, lower and 
 lower, till he sets in the West. It appears to us that the 
 Sun is moving round the Earth, day after day, giving 
 light and warmth to us, as we need it, by the Wise and 
 Gracious Will of our Father in Heaven. Tor a long time 
 even the wisest philosophers thought so too. And so in 
 the Bible you find it written that the Sun " cometh forth 
 as a bridegroom out of his chamber, and rejoiceth, as a 
 strong man, to run a race. His going forth is from the 
 end of Heaven, and his circuit unto the ends of it." But 
 of the Earth the Psalmist wrote, "He hath made the 
 round world " — by which he meant, not the round globe, 
 as we speak of it, but the Earth, as men thought of it in 
 those days, lying spread out before them on all sides, 
 rounded in with a circle — " so fast, that it cannot be 
 moved." 
 
 38. We must not wonder at this. For the Bible was 
 not given us to make us wise in matters of this kind. God 
 means us to search out these things for ourselves by 
 degrees, more and more, by using the powers of mind 
 which He has given us. We must not expect Him to 
 teach us such things as these out of the Bible. The Bible 
 is given to teach us about Goodness and Truth, about 
 things which concern the heart and the conscience, about 
 God's Love to us, and our duty to Him and to each other. 
 
28 FIRST LESSONS IN SCIENCE. 
 
 It is not meant to teach ns about matters of science at all. 
 We must not suppose that the Holy Spirit of God would 
 all at once reveal to the good men, who wrote the books 
 of the Bible, such knowledge as this, so that they should 
 come in a moment to be wiser than other people who lived 
 in their days, about these things — about the Earth and 
 the Moon and the Sun and the Stars, or about any of those 
 things which God means us, as I have said, to find out for 
 ourselves by hard labour, and by the proper use of the 
 powers which He has given us for that purpose. And so 
 we find that the writers of the books of the Bible, whose 
 hearts were taught the highest wisdom by the Spirit of 
 God about matters of Truth and Love, and those things 
 which concern the spirit of man, had very little know- 
 ledge, far less than God has now given us, about matters 
 of science. 
 
 39. And, indeed, a man may do great good, and serve 
 God truly with his body, soul, and spirit, which are 
 God's, without knowing much of these things, or without 
 knowing them at all, if God has not been pleased to give 
 him the power of knowing them. But, if God sees good 
 to grant to any of you any knowledge of these things, as 
 He does now to you who are reading this little book, then 
 be sure that He means you to use the power He gives you, 
 that so you may have higher and deeper thoughts of His 
 Wisdom and Greatness and Goodness, than you could have 
 had without it. Just so a little child may be a very good 
 child, and do the Will of his Father in Heaven, though he 
 has not the knowledge even of common things, which a 
 full-grown man has. And yet the full-grown man, because 
 he knows more, is able to do more and higher work in the 
 world, to serve God with his mind, as well as with his 
 heart and soul and strength. And whether we know 
 much or little of matters of science, the Bible is still the 
 
FIRST LESSONS IN SCIENCE. 29 
 
 Book of Books to teach us of our Father's Love and of His 
 Heavenly Kingdom. And the same Good Spirit who 
 taught of old the hearts of the holy men who wrote the 
 books which make up the Bible, graciously teaches our 
 hearts too, when we come to study it with an earnest, 
 humble, desire to know more and more of His Truth, and 
 of the way of Life Eternal. 
 
 40. At first, then, as I have said, even philosophers, who 
 studied these matters, supposed that the Earth stood still, 
 and that the Sun went round it. And it was easy enough 
 to believe this, when they thought only of the Sun, and 
 when they knew nothing of its vast bulk, which we now 
 know to be more than a million times as large as that of 
 the Earth. But, besides the Sun, there is the Moon too 
 that rises in the Bast and sets in the West, as the Sun 
 does. And besides the Sun and Moon, there are hundreds 
 and thousands of Stars that do the same ; and we know 
 also that almost all of these Stars are as large as the Sun 
 and larger. Let us stop a few moments to think about 
 this. I cannot now show you how these things are known. 
 But I wish to give you some clearer notion than you yet 
 possess of the size and distance from us of those bright 
 bodies of the sky. The Moon, then, is found to be 240 
 thousands (240,000) of miles away, the Sun 96 millions 
 (96,000,000) of miles, that is, 400 times as far off as the 
 moon ; and the nearest Fixed Star is at least twenty 
 billions (20,000,000,000,000) of miles away from us, that 
 is, more than 200,000 times as far off as the Sun. I say 
 the nearest Fixed Star, because there are a few stars, called 
 Planets, or Wandering Stars (the reason of which name 
 you will see presently) which are much nearer to us. 
 But only four or five of these can be seen by the naked 
 eye. Except, however, these four or five, it is certain that 
 each of the bright points we see sparkling at night must 
 
30 FIEST LESSONS IN SCIENCE. 
 
 be, at least, as far off as this, and most of tliem are very 
 much farther off. 
 
 41. But you will get very little notion of what this 
 means, merely by knowing these numbers. Suppose that 
 a man can travel — not 50 miles a-day, as before, but — as 
 fast as he can go by a steam-train along a railway in 
 England, say 100 mUes in 3 hours. And suppose him to 
 go on at this rate, day after day, day and night, without 
 stopping for rest and food. It would take him just 300 
 days to reach the moon ; whereas it would take him 400 
 times as long, that is, 120,000 days, or nearly 830 years of 
 365 days each to reach the Sun. 
 
 But how long would it take him to reach the nearest 
 fixed Star ? Why, suppose that in one single day he could 
 travel the whole 96 millions of mUes, and get to the Sun, 
 and that he went on at this rate from day to day, it would 
 take him more than 200,000 days, or nearly 650 years of 
 such travelling, before he could reach this Star. No wonder 
 that the Stars appear so small! But what huge bodies 
 they must be, and how very bright they must be, even to 
 be seen at all at such a distance ! 
 
 42. And that bright light of the Stars, how long will 
 it be in coming to us ? For light takes time to travel, as 
 well as sound, though it travels very much more quickly 
 than sound. You know that sound takes time to travel. 
 For when you see the flash of a distant gun, you have to 
 wait some time before the sound comes, and all that time 
 it has been coming to us, at the rate of about a mile in five 
 seconds. But the flash of the gun seems to reach us in a 
 moment, because light travels so very quickly, and the 
 distance is so short. And yet light does take time to 
 travel, as we find when we have to do with greater 
 distances. It is found that the light of the sun takes 
 about 8^ minutes to reach the Earth. But the Ught of 
 
FIEST LESSONS IN SCIENCE. 31 
 
 the nearest fixed Star nmst take more than 200,000 times 
 as long, that is, ahont 3^ years. In other words, the light 
 hy which we see such a star at any moment, must have 
 left it 3 J years ago, before it reaches our eyes. But there 
 are other stars more distant, whose light must have been 
 2000 years or more in coming to us. So that when we 
 mark the places in the sky of such stars, judging by the 
 light which comes to us, we mark the places which they 
 had 3:|- or 2000 years ago, not those which they have now. 
 
 43. Then again, as to size, we can say nothing certainly 
 of the size of the Fixed Stars, except what has been said 
 already, that they must be of immense bulk, as well as 
 brightness, to be seen at all, being at such a great distance 
 from us. The diameter of the Moon is about one-fourth 
 that of the Earth, or 2000 miles, so that the Moon is a 
 much smaller body that the Earth. But the Sun's 
 diameter is 110 times that of the Earth, or 880,000 miles ; 
 and his bulk is vast indeed. Let me try to give you some 
 means of judging this bulk. If the Sun could be placed 
 with his centre at the centre of the Earth, then the Earth 
 would be like a little pea in the middle of his huge globe. 
 And since the Moon's distance from the Earth is only 
 240,000 mUes, while the distance of the Sun's surface 
 from his centre — that is, his radius — is half his diameter 
 or 440,000 miles, it is plain that the body of the Sun will 
 stretch out on all sides almost as far again as the Moon, 
 which, though hanging so far off in the air, would yet be 
 inside the gi-eat globe of the Sun's body, like a pin's head, 
 somewhere, half way between the centre and the surface. 
 
 44. What shall we say then about all these ? Must we, 
 indeed, suppose that this little pea of an Earth stands still 
 — for now we must call it little, when we are thinking of 
 the Sun a million times as large — and that all these 
 glorious hosts of mighty worlds, to each of which the 
 
32 FIRST LESSONS IN SCIENCE. 
 
 Earth, is but as a pin's head to the head of a man, are moving 
 daily round it, at distances so vast that we have scarcely 
 power to measure them |it all? Or is it not far more 
 simple to suppose — as that will explain what we see daily 
 of the rising and setting of the Sun and Moon and Stars — 
 that these great Suns are all standing still, each one in its 
 place, and that the Earth turns round each day on its 
 axis, and so they only appear to move round it ? I am 
 speaking, observe, only of their rising and setting. It is 
 only those motions of the heavenly bodies that are ex- 
 plained in this way. The fixed stars, indeed, appear to 
 have no other motions : you may see them rise and set 
 always at the same points of the sky. But if you look 
 with oare, you will see that the Sun, and the Moon, and 
 the Planets, are always changing from day to day their 
 place of rising and setting. And I hope to show you 
 by and bye the reason of this also. 
 
 45. But there are proofs enough to make men certain 
 that it is, indeed, the Earth itself, and not the Sun and 
 Moon and Stars, that is moving, when they seem to rise in 
 the East, and go up high above our heads, and then sink 
 down and set in the West. It is the Earth itself, then, 
 turning round from West to East once a day on its axis; 
 and so bringing, bit by bit, each part of its whole sur- 
 face, with the people and places that are on it, first into 
 sight of the sun at sunrise^ then to pass under his hot 
 rays, when he rises highest, at noon, and then to lose 
 sight of him again at sunset. And then the Earth still 
 turns on, and they are carried round away out of the 
 Sun's light and warmth. And so the day passes into 
 night for them ; and just twelve hours after high noon 
 they are wrapped in midnight darkness, vsdth. only the 
 light of the Moon, it may be, and the Stars, if the night 
 be clear, to lighten it. It is the huge Earth, also, which, 
 
FIRST LESSONS IN SCIENCE. 33 
 
 turning in this way, makes the Moon and the Stars 
 seem to rise, and mount, and sink, and set, just as the 
 Sun does. 
 
 From this, too, we see that the place, to which a 
 person points when he speaks of heaven being up above 
 his head, will not be the same at all parts of the same day, 
 though he may be standing in the same spot, and in the 
 same posture. It, will, in fact, be changed each moment, 
 as the Earth turns round, and he is carried round with it. 
 But, when he points down, he will always be pointing to 
 the same place, if he does not shift his feet ; for he will 
 always point to the Earth's centre, just beneath him, and 
 call that " down." 
 
 46. So then, learned men know this rate, at which the 
 Earth is now turning on its axis, namely, once in twenty- 
 four hours. And some suppose that it turned at the same 
 rate as this, when it first came forth, brought into its 
 present form by its Mighty Maker's Word, and launched, 
 as it were, into space from His Hand. And now, having 
 found out, partly by actual measuring, partly by their 
 own skill, the length of the Earth's shorter diameter, they 
 were able, as I have said, to reason out for themselves 
 upon paper, without any need to measure it at all, the 
 length of its long diameter ; that is, they were able to find 
 out what ought to be the length of the longer diameter, if 
 the Earth was, indeed, at first a fluid mass, spinning 
 round on its axis at this rate. They did reason this out 
 on paper ; and they found it to be just the length, which, 
 when made out in other ways, partly by actual measure- 
 ment, partly by their skill, it is found to be — namely, 
 longer by twenty-six miles than the length of the shorter 
 diameter. 
 
 Thus, then, they saw that there were indeed good 
 grounds for saying that, when the Earth was first formed 
 
34 FIRST LESSONS IN SCIENCE. 
 
 it was a fluid mass, turning round upon a central axis ; 
 which fluid whirling mass, hy virtue of the attraction 
 which each particle of matter exerts upon all other 
 particles, formed itself into its proper shape, and settled 
 down in the form of a glohe as now we see it, with the 
 longer or Equatorial diameter twenty-six miles longer 
 than the shorter or polar diameter. 
 
 47. " But if the Earth was at first a fluid mass, yet why 
 a hot fluid mass ? why made of red-hot molten matter ? 
 Might it not have been made of cold fluid like the sea, in 
 which might be floating, mixed up like sand and soil in 
 the muddy waters of a flooded river, all those kinds of 
 matter, which now make up the solid crust of the Earth, 
 and which settled down, perhaps, and got hardened into 
 rocks?" 
 
 No ! for many reasons this could not have been the case. 
 We Gould not then account for the greater part of the 
 Earth's crust at all; since the main portion of it, that 
 which lies under all the rest, as far as we are able to 
 judge, such as the hard rock called granite, is plainly 
 seen, when we come to look at it closely, to be matter 
 that was once in a molten state. Again, those beds or 
 layers of matter, which are found lying next above the 
 former, bear marks also of having been changed by heat, 
 though there is no doubt, when we look closely into them, 
 that they were formed at first in beds by the dropping of 
 some kind of sand or other, through long ages, at the 
 bottom of the sea. They seem to have been altered by 
 being so close to the hot mass of matter beneath them, 
 which had so far cooled down from the fluid state, as to 
 have become by this time hard solid rock, but gave out 
 still intense heat. Besides this, it is certain that vast 
 masses of melted matter have often since then been thrust 
 up from the inner regions of the Earth's body through 
 
FIRST LESSONS IN SCIENCE. 35 
 
 cracks in tlie crust, and have been poured out in this fluid 
 state over -what was then the surface, and so by degrees 
 cooled down and hardened into roots. 
 
 48. And what is more than all this, such masses of red- 
 hot liquid matter are still being thrown up in many parts of 
 the Earth. Here and there we find high mountains, called 
 volcanoes, from the tops of which from time to time are 
 poured forth streams of such matter, which go rolling 
 down the mountain-side, like rivers of fire, and press on 
 in their fearful course, flowing over fields and gardens^ 
 and sometimes over whole towns and villages. At last 
 the mighty power, which forced up the fiery flood, has 
 spent its strength for the time ; the torrent ceases to flow ; 
 and then this matter, called lava, cools down into thick 
 beds of solid rock. In other parts of the Earth there are 
 hot springs, called Geysers, which throw up, sometimes to 
 a great height, with a fearful roar, hot boiling water 
 from the deep bowels of the Earth. 
 
 All this is enough to show that there must even now be 
 a glowing mass of red-hot liquid matter, within the body 
 of the Earth under our feet. And on going down deep 
 below the surface of the Earth, as men do in mines, where 
 they dig far down, searching for stones out of which they 
 may, by melting them, obtain gold, silver, tin, iron, lead, 
 and other metals, they find the heat increase as they go 
 deeper and deeper. And we have reason to believe, that, 
 could they get further down towards the Earth's centre 
 than the very little way which they can go (for the 
 deepest mine is not much more than half a mile deep from 
 the surface), they would find it very hot indeed, too hot 
 at last to be endured, hot enough to fuse or melt the 
 hardest rock of which the Earth's crust is made. 
 
 49. From all this we must conclude that, at this very 
 moment, our feet are standing on the outer coating of a 
 
 D 2 
 
36 FIEST LESSONS IN SCIENCE. 
 
 great globe, -wMcli is full of red-hot molten matter. We 
 cannot tell the exact thickness of this outer solid coating. 
 We do not know whether or not, like the rind of a , 
 pumpkin, it is pretty nearly' of the same thickness all 
 round. We only know the thin outer crust of this coat- 
 ing, like the skin, which we might shave off the outside 
 of the rind of a pumpkin. All that we can be certain of 
 is this, that this outer coating is, at all events, more than 
 ten miles thick, perhaps, nowhere less than forty or fifty ; 
 and some have thought that it may be formed into caverns 
 or hollows on its inner surface, so as to be in some places 
 much thicker than in others — perhaps, here and there, 
 even a hundred or a thousand miles thick, about one- 
 fourth of the whole way down to the Earth's centre. But 
 there it is in the centre of the Earth, this red-hot molten 
 mass, in the middle of the great globe, where all sorts of 
 matters are mixed up, it may be, and fused into one boiling 
 whole, of which portions come off to us at times, forced up 
 from beneath in the form of Lava. Once the whole globe 
 was a mass of liquid fire. Then the outer crust cooled 
 down and hardened. And year by year we may believe, 
 or rather, age by age — for we cannot speak of days and 
 years when we are talking of such matters as these — the 
 Earth's body cooled down, as it is still cooling down. 
 Perhaps one day it will be too cool in all parts of its 
 surface for such being as we are to live on it at all. 
 
 50. You will now be able to have some clearer notion of 
 the way in which the Earth's crust has been formed. 
 From what has been said you will see that we have good 
 reason to believe that the Earth, when first brought into 
 its present form, was merely a red-hot liquid mass. With 
 such heat as this, all the water which we now see could 
 only exist in the form of hot vapour or steam. And 
 many other kinds of matter, which now appear either in 
 
FIEST LESSONS IS SCIENCE. 37 
 
 a solid or a liquid form, could only have existed, like 
 
 water, each in its own proper form of vapour, or gas, as it 
 
 is called. These gases, niixed up with steam, and the 
 
 matters, which make the air which we now breathe daily, 
 
 would surround the fiery globe of red-hot matter with a 
 
 dense cloud. In process of time the surface, throwing off 
 
 heat without ceasing into the vast regions of space, must 
 
 have cooled down enough for a thin outer crust to have 
 
 been formed upon it. On this cruet would be dropped by 
 
 degrees a number of little particles of matter out of the 
 
 thick cloud, so fully charged with them, which wrapped 
 
 the globe round about; for some of the many things 
 
 mixed up in it would begin, as the surfaced cooled even a 
 
 little, to leave the state of gas, and appear in a solid form. 
 
 So too the vapour would at last fall down, like dew, upon 
 
 the cooling surface, as you know that steam will form 
 
 drops of water upon any cooler thing, even upon a man's 
 
 warm hand, when plunged in the midst of it.* 
 
 51. " But what will the Sun have been doing all this 
 
 while?" It will, doubtless, have been shining then as 
 
 now, and its heat will have reached the Earth then as it 
 
 does now. But w^e know that at this time, in some parts 
 
 of the Earth, the Sun's heat is much greater than in 
 
 others ; and in all places his heat is felt in some parts of 
 
 the year much more than in others. In some places 
 
 the people suffer much from intense heat ; in others they 
 
 can scarcely live for the bitter cold. Something of this 
 
 kind took place then as now. All parts of the crust, we 
 
 may believe, were warm then because of the red-hot mass 
 
 * " Nothing that is said here must be taken as either afBrmiug or 
 denying any theory of the origin of the solar system from ono coherent 
 mass of nebulous matter, split up into independent bodies by the pro- 
 cess of cooling and contraction. Some such hypothesis may, it is not 
 unlikely, be generally received hereafter. "We cannot say that it has 
 been so received yet; and the author was dealing only with facts 
 which may fairly be regarded as established." 
 
38 FIRST LESSONS IN SCIENCE. 
 
 SO close inside of it. But some parts were more heated by 
 the Sun than others. As far as the eifect of the Sun's 
 warmth went, there would have been icy cold in some 
 places and scorching heat in others. This alone would 
 make the Earth's surface to cool more quickly in some 
 parts than in others; and this would cause huge cracks 
 and chinks all over the crust. Great pieces might be 
 broken off in this way from the rest, and float, free, as it 
 were, upon the fiery deep. And some of these being 
 more cooled, and therefore more solid and heavy than 
 others, would begin to sink downward towards the centre 
 more than others. Down, down, they would go by slow 
 degrees; and, as they sank, they would press upon the 
 molten mass beneath, and drive it slowly up to spread 
 over the surface. Here it would ooze up through smaller 
 chinks or holes ; there it would be pushed through vast 
 gaps, which had been rent in the Earth's crust. 
 
 52. And now this fluid matter, thus pressed up from 
 beneath, would cool and harden into rocks ; while the 
 sunken portions of the Earth's crust would now make the 
 beds of seas, forming hollows into which the new-made 
 water would flow. And on the surface of such water, as 
 well as upon the dry land, would still be ever dropping 
 from the dense cloud that hangs about the Earth, fresh 
 stores of fine matter, as one substance after another 
 quitted its airy form of gas, and began to appear in a 
 solid or liquid form ; and thus, partly by ' means of 
 matter thus dropped into it, partly by means of other 
 matter washed off the surface of the land, as rain began to 
 fall, and rivers to flow, there would be formed by degrees, 
 at the bottom of these first seas, beds of solid matter, mud, 
 and sand. Such a bed as this is called a layer, or stratum, 
 from a Latin word which means " laid " or " spread out ; " 
 but when we speak of more layers than one, then, by the 
 
FIRST LESSONS IN SCIENCE. 39 
 
 laws of the Latin language, we must use the plural form, 
 and say strata. Such strata, when pressed down from 
 above by the weight of other matter, and pressed up from 
 beneath, would in course of time become hardened into rock. 
 
 53. Suppose now that, through the cooling of the 
 Earth's crust, more in some places than in others, a great 
 crack or chink was made on the border of such a sea as 
 this, of which we have just been speaking, or, perhaps, 
 even under it, in its very bed. Down, down, at once into 
 the abyss thus opened would rush the waters of the sea, 
 and come into contact with the molten fluid beneath. 
 And what would then be sure to happen ? Who does not 
 know the fearful force with which water expands, that is, 
 spreads out on all sides into steam, when even a small 
 mass of it is changed quickly by intense heat ? "Who does 
 not know that a common kettle, if the spout were plugged 
 up and the top tied down, would be burst and torn to 
 pieces by the steam, formed by a very little water, shut 
 up inside and heated ? So would it be when the water of 
 such a sea was heated by sudden contact with the red-hot 
 mass within the globe. Though very little water may 
 have entered by a narrow cleft or fissure only, it would be 
 changed all at once into steam, and become a mighty 
 giant, as it were, tearing up with fearful fury the whole 
 bed of the sea above, hurling here and there the broken 
 fragments of the crust, or piling them up in heaps, one 
 upon another. 
 
 54. In this way we can conceive that the crust of the 
 Earth would begin to be broken up, and covered over 
 with hills and mountain-masses, so as quite to lose the 
 smooth even form, which it may once have had when first 
 launched into space. And the crust would cool more and 
 more, as time passed on, and grow thicker and thicker all 
 over, both by reason of this cooling from within, and also 
 
40 FIRST LESSONS IN SCIENCE. 
 
 by the constant dropping of matter tliat was still held 
 floating in the form of gas in that thick cloiid. At last 
 iShat cloud would itself be cleared away, when it had 
 parted with its contents, except the air which we breathe, 
 and the vapours which still float aloft from time to' time 
 in the form of common clouds. And now, in course of 
 time, the Earth's surface will have cooled enough to allow 
 of plants and living creatures being placed upon it. And 
 God gave the Word, and they were made. As He saw 
 good He brought them forth, suited to live upon the 
 Earth, not as it is now, but as it was then. And when 
 He saw good, all these died off, and were seen no more. 
 Some change took place in the state of things over the 
 whole Earth, we cannot say what for certain — ^perhaps, 
 some change in respect of heat and cold — not a quick 
 sudden change, it may be, but a slow and gradual one — 
 which caused all these living things of all kinds, that 
 were first made, to die off and pass a;way, so that their 
 very races came to an end and were seen no more. 
 
 55. And then God made new the face of the ground. 
 He made other living creatures, and other plants; and 
 ages again passed on, and changes took place. The 
 Earth's crust got thicker as it cooled; some parts sank 
 down as before, others were lifted up from beneath. And 
 so new mountains were raised, and new seas were formed 
 in the hollows ; and at the bottom of those seas was 
 dropped new matter, washed off from the hills by rain, or 
 driven up from beneath, from the mouths of fiery moun- 
 tains, or other chinks in the crust. And, when God saw 
 good, all this too was changed. All these living creatures 
 also died off by degrees ; they, and their very races, passed 
 away at last, and were seen no more. And then God 
 made others, fit to live upon the Earth in the state it then 
 had reached. And ages passed away, long ages, while 
 
FIRST LESSONS IN SCIENCE. 41 
 
 these lived on ; and the earth, cooled more and more, and 
 its crust got thicker and thicker; and some lands sank 
 down, as before, either slowly or suddenly, and became 
 the beds of seas, while others were lifted up, and became 
 mountains; and so the face of the Earth was changed 
 once more, while new forms of rock were made in the 
 ocean beds. Again and again all this took place. The 
 old races of plants and living creatures died out and passed 
 away, and new races were called into being, from time to 
 time, by the Word of God ; and the face of the Earth was 
 changed, and new forms of rock were made in the ocean 
 beds. At last the Earth was fit for man to live on : and then 
 he was formed and placed upon it, with all the living 
 creatures, trees, and plants, that we now find around us. 
 
 56. We cannot pretend to explain each step of the 
 wondrous process by which the great Earth was thus 
 brought out of its first liquid form into its present state. 
 But the above will give you some notion of the way in 
 which, as philosophers believe, the changes upon its sur- 
 face took place. Of these changes themselves we have 
 the certain proofs before us. We have only to dig up 
 stones buried beneath our feet in the Earth's crust, or to 
 look at them as they stand bared to our view upon a 
 mountain-side ; and we may read the tale which they tell 
 us of what must have taken place on the Earth ages 
 before the first man was made. We cannot, indeed, be 
 sure of each minute point ; but we can be sure of the main 
 truth of the matter. We are certain that the rocks of the 
 Earth's crust must have been made in some such a way as 
 this which I have told you, and that such rocks are still 
 being made in the depths of the sea. We are certain that 
 such races of plants and living creature have lived, and 
 died, and passed away from the Earth, because we find 
 their remains — the bones of beasts, and birds, and fishes. 
 
42 PIEST LESSONS IN SCIENCE. 
 
 and reptiles — the shells of snails and shell-fish, the wings 
 of flies and other insects, the roots and trunks and leaves 
 of trees and plants — buried up in immense numbers in 
 the middle of hard stones dug out of the solid rock. 
 
 57. These remains are called fossils, or things dug up, 
 from the Latin word fossus, dug. Sometimes these things 
 are found unchanged in any respect from what they were 
 when first buried up. Very often the particles of matter, 
 of which the fossil thing was made at first, have been 
 withdrawn one by one by the silent working of God's 
 Laws, and particles of some other kind of matter have 
 taken their place, yet so as still to preserve the exact form 
 of the thing. In this way a bone, for instance, or a log 
 of wood, may be turned to stone, the small particles of 
 bone in the one case, and of wood in the other, having one 
 by (5ne been taken away, and particles of stone having got 
 into their place ; and yet the form of the bone and of the 
 log will remain all the same. Such things as these are 
 said to be petrified, or turned into stone, and the fossils are 
 called petrifactions. Sometimes, again, there is merely a 
 print of the plant or living creature, left once upon the 
 mud or sand, .which has since hardened into stone. We 
 may see before us, taken out of a solid mass of rock, the 
 bones and tfeeth and scales of an animal, the markings on 
 its skin, the exact form of its eye, the model of its softest 
 parts — the stomach, for instance, with its very contents 
 at the time of death, the bones of one creature being found 
 within the body of another that preyed on it. All these 
 are clearly seen, as if the very thing itself were before us 
 that died and passed away with its whole race, thousands, 
 or it may be millions, of years ago. We find the remains 
 of fish so perfect, that not a scale is out of its place or 
 wanting. The finest lines upon the wings of flies are 
 fixed upon the stones, and sometimes their very colours. 
 
FIRST LESSONS IN SCIENCE. 43 
 
 58. And these are only some of tlie wondrous things 
 which these rocks reveal. Most curious footprints are left 
 of strange creatures that lived in those days, of monstrous 
 frogs and enormous birds. In some places we have marks 
 on stone, which show that the layer of matter of which 
 it was made had dried and cracked before the next layer 
 was laid down upon it. These open cracks have served 
 as moulds, of which casts or copies have been taken in 
 relief, as it is said, that is, standing out to view on the 
 lower surface of the upper layer. These have now hard- 
 ened into stone, and look not unlike the stone mullions of 
 church windows, so that a person might almost think, on 
 first looking at them, that they were made by the hands 
 of man. The very ripple-mark is seen which the sea must 
 have left upon the shore, as it does now upon a sandy 
 beach, where the water is shallow, when the tide is going 
 out. The mark so left by one tide must have hardened 
 before the next came in. The new sand thrown over it 
 did not destroy the marking ; it only covered it up, and 
 itself took upon its under surface the form of the ripple 
 it buried. And so now in quarries may be dug up stones, 
 showing both the ripple itself and the mark made by it 
 on the sand, which was spread over it by the next tide 
 and buried it; but the sand, both above and below, is 
 turned to sandstone. Nay, if one walks along a soft 
 sandy beach after a heavy shower, he may see that the 
 rain has pitted it all over with samll holes, each with the 
 sand raised up, like a little cup, around it. And such 
 holes as these have been found upon the surfaces of sand- 
 stones which bear the ripple-marks. And these little 
 oups are seen to have the ridge raised round them higher 
 on one side than the other, which shows that the sand in 
 those old days was driven up in this way by the, force 
 with which the rain came, and helps us to tell the very 
 
4i FIKST LESSONS IN SCIENCE. 
 
 point fiom whicli tlie wind blew when these stones were 
 made. 
 
 59. But there is something yet still more strange to be 
 told. There are whole masses of rock, made up wholly of 
 the cast-off ilinty skins of little creatures, so very minute 
 that they look like the finest dust or flour to the naked 
 eye ; and their true nature can only be seen when they 
 are viewed by the help of a very strong microscope. This 
 matter is called tripoli, and is used as a powder to polish 
 stones and metals. In Norway a similar powder had long 
 been used for food in time of famine, and Hence it had 
 the name given to it of mountain-meal. It used to be 
 thought that these were the skins of little animals. It is 
 certain that the creatures to which they once belonged 
 had life and proper organs by which that life was kept in 
 being and passed on to others. But it is now thought 
 that these creatures were plants of a certain kind, not 
 animals. So very small are these flinty skins, that fifty 
 thousand millions of them would only fill up a common 
 thimble. And yet on these minute plates are seen fine 
 graceful lines and markings which serve to divide them 
 into classes. How awful is the Power and Wisdom of the 
 Lord God Almighty! The smallest creature, made by 
 His Hand, is perfect, and has a beauty which we may 
 get a glimpse at, but which no eye can fully see but His 
 who made it. 
 
 60. But during all these ages, passing all our powers 
 to calculate or imagine, there was no man on the Earth to 
 till it, no one to see its beauty and to tell the Greatness 
 and Goodness of God. Hosts upon hosts of living crea- 
 tures were brought into being, and died and passed away. 
 Their very kinds appear no more on Earth. But there 
 was no human eye to note their forms or take account of 
 their doings. The forest-tree tossed its branches; the 
 
FIRST LESSONS IN SCIENCE. 45 
 
 meadow flowers bloomed ; bright colours beamed on every 
 side. The Lord God " gave rain from heaven and fruitful 
 seasons " for the multitudes of living things who then 
 looked Tip to Him as they do now. Sweet scents were 
 spread abroad, on every side sweet sounds were heard. 
 And God was there, to see the works which He had 
 made, and " behold ! they were very good." 
 
 Yet, after all, Man is ; the Great Creator has brought 
 him forth in His own good time, a creature utterly dif- 
 ferent from any other, that has left traces of its being in 
 the rocks of bygone ages — Man made in the likeness of 
 God, Man to know God, Man made to have converse with 
 God. It cannot be that he is meant, as the creatures of 
 former ages, however monstrous or beautiful, only to do 
 a passing work, to eat and drink, and live and die and 
 perish. A being made in the image of God must be made 
 for Eternity. His work upon Earth must be " to glorify 
 God with his body, soul, and spirit, which are God's." 
 His part is to be the Priest of Nature, to lift up, day by 
 day, as he alone can do, a thankful heart and voice, and 
 to bring forth the fruits of Truth and Love to the Praise 
 of his Maker's Name. 
 
46 FIEST LESSONS IN SCIENCE. 
 
 PAET II. 
 
 1. All wHcli you have just been hearing is so strange, 
 it so fills the mind with -wonder and awe when we think 
 of it, that I must one day tell you something more ahout 
 it — I mean about these traces which are left, buried up 
 in the hard rock, of creatures that have once lived upon 
 the Earth, and of the mighty changes that have taken 
 place upon its surface in the ages long gone by. But I 
 must do this in another book. I must now go on to tell 
 you something about the Sun, and Moon, and Stars, and 
 that branch of Science which teaches about these things, 
 and which is called Astronomy, that is, the Law of the 
 Stars. 
 
 2. And here let me first say that, besides the motion 
 which the Earth has of turning round upon its axis once 
 in twenty-four hours, which we call a day, it has another 
 motion, that of going round the Sun, spinning ever as it 
 goes, once in 365 days, which we call a year. And not 
 only does the Earth go round the Sun ; all the Planets 
 also do the same. The Sun is the great King, as it were, 
 with his enormous bulk and mass, who rules all these 
 lesser bodies. The Eixed Stars are all Suns, having light 
 of their own. But the Planets all get their light, as the 
 Earth does, from the Sun. And those which are nearest 
 to the Sun get, of course, the most light and heat from 
 him. Four or five of these Planets, as you have been told 
 before, can be seen by the naked eye. But there are forty 
 
FIEST LESSONS IN SCIENCE, 47 
 
 or fifty more which, from heing either very small, or 
 very far off from us, cannot be seen without the help of 
 a telescope. These Planets all, like the Earth, go round 
 the Sun in circles, or rather in curves which are very 
 nearly circles, each at its own distance, some being nearer 
 to the Sun than the Earth, and some farther off. Here is 
 a Table of the distances from the Sun of the chief Planets, 
 with the names by which they are known (names of old 
 Greek and Boman gods and goddesses), and also of the 
 length of their Years, that is, of the time they take to go 
 round the Sun, each in its own proper circle. 
 
 Table op the Eight Chief Plauets. 
 
 Name. Distance from the Sun. Length of Year. 
 
 Mercury .. .. 37 millions of miles 88 days. 
 
 Venus 69 225 
 
 Earth 96 365 
 
 Mars 146 687 
 
 Jupiter 500 4833 
 
 Saturn 916 10759 
 
 Uranus 1842 30687 
 
 Neptune .. .. 2884 60127 
 
 3. Uranus and Neptune cannot be seen by the naked 
 eye, being very distant from the Earth. But they are 
 very large Planets, Uranus being about 64 times as large 
 as the Earth, and Neptune 125 times as large. Saturn 
 is also very distant, but he is not so far off as they, and 
 being also very large, nearly 1000 times as large as the 
 earth, he can be seen by the naked eye. But Jupiter and 
 Venus are by far the most splendid of these stars, as seen 
 from the Earth. Jupiter is the largest of all the troop of 
 Planets, being .1331 times as large as the Earth; and, 
 being always nearer to the Earth than Saturn, even when 
 Saturn is nearest to us and Jupiter farthest off, he appears 
 always bright and large. But when he is nearest to us — 
 
48 FIEST LESSONS IN SCIENCE. 
 
 when tlie Earth, and Jupiter, going round the Sun, 
 each in the proper circle, happen to he on the same side 
 of the Sun — then indeed he is a brilliant object in the 
 sky. Hence the ancients gave him the name of Jupiter, 
 the king of the gods. Venus was the Eoman name for 
 the goddess of beauty, and they gave* this name to the 
 second Planet on the list, which, though a little smaller 
 than the Earth in size, is yet so near to us, and so near 
 to the Sun also, basking, as it were, in the full blaze of 
 his light, that she is always a very bright and beautiful 
 Star whenever she is seen in the heavens. Being so near 
 the Sun, however, she can only be seen in that part of 
 the sky where the Sun is. Sometimes she is so bright 
 that she can be seen even in the day-time. But the Sun's 
 dazzling rays are most commonly too strong to allow her 
 light to be seen by our eyes when the Sun is high. She 
 is generally seen about sunrise or sunset, and is often a 
 bright Morning Star in the East an hour or two before 
 the Sun rises, or a bright Evening Star in the "West 
 shortly after the Sun has set. At certain times Venus 
 may be seen to pass between the Earth and the Sun, and 
 to make what is called a transit, that is, a passage across 
 the Sun's face, when she is seen clearly as a small round 
 black spot. Mercury also is very close to the Sun, and, 
 being only about one-fifteenth of the size of the Earth, he 
 cannot be seen by the naked eye, except, now and then, 
 just before sunrise or just after sunset, or when, like 
 Venus, he makes a transit across the Sun's face. He goes, 
 as you see by the Table, very nimbly round the Sun, four 
 times while the Earth goes once. Hence he got the name 
 of Mercury, since the Eoman god of that name was sup- 
 posed to be the messenger of the gods, and to run with 
 great speed. Mars is about one-seventh the size of the 
 Earth, and, from its having a kind of ruddy colour — 
 
FIRST LESSONS IN SCIENCE. 49 
 
 perhaps from the red colour of the rooks upon its surface 
 — it has had the name given to it of Mars, the Eoman 
 god of war. 
 
 4. Between Mars and Jupiter lie more than forty small 
 bodies, so small that they cannot be seen by the naked 
 eye ; and on that account they are often called Planetoids, 
 that is, Planet-like bodies rather than Planets. The 
 largest of them is about 600 miles across, the smallest of 
 them about 100 miles across. It would take 2000 of the 
 former and half a million of the latter to make up a body 
 as big as the Earth. If we subtract Mercury's distance 
 from the Sun from the distance of each of the other chief 
 Planets, as given in the Table, we shall obtain the fol- 
 lowing numbers : 32, 59, 109, 463-, 879, 1505, 2847. Now 
 it will be seen that each of these numbers is about double 
 of the one before it, except that there seems to be a sort 
 of break between 109 and 463, as if a number was wanting 
 here to be the double of 109 (as, for instance, 218), and 
 then 463 would be nearly the double of this number, and 
 the row of numbers would be complete, each the double 
 of the one next before it. This led some persons to think 
 that there must be a planet somewhere between Mars and 
 Jupiter ; and, in searching for it, the first little Planetoid 
 was found on January 1, 1801. Up to the year 1845 only 
 four such small bodies had been discovered. But since 
 tJien almost every year has added to their number, and 
 there are now some forty or fifty of them known, and 
 perhaps there are more which will yet be discovered. 
 They are supposed, with good reason, to be broken pieces 
 of some larger Planet, which once went round the Sun 
 between Mars and Jupiter, but was burst from some 
 violent internal convulsion, or from some other cause. 
 
 5. Uranus was discovered by Sir William Hersohel in 
 1781. Neptune was discovered in 1846 in. a very re- 
 
50 FIEST LESSONS IN SCIENCE. 
 
 markable way. It was long known that the motion of 
 Uranus in its path was not qnite regular — that it was 
 sometimes a little before and sometimes a little behind 
 the place where it ought to have been, according to the 
 calculations of astronomers. And it had been suggested 
 that this might possibly arise from its being attracted by 
 some other Planet not yet known, whose orbit was outside 
 that of Uranus. This was a mere guess, however, and 
 for many years no one thought of going further into the 
 question. It was taken for granted that if there was 
 such a Planet it would some time or other be found. 
 However, in the year 1846 two very able astronomers, 
 one a Frenchman named Le Verrier, the other an 
 Englishman named Adams, each not knowing what the 
 other was doing, made at the same time a calculation on 
 paper, by observing how much at different times the 
 motion of Uranus was disturbed, to see if they could not 
 reason out what must be the size and place of a Planet, 
 whose orbit should be outside the orbit of Uranus, to 
 produce these effects. They both went through the very 
 long and diiEcult enquiry, and they agreed in fixing 
 nearly the same place in the sky as the place where such 
 a Planet would be seen at a certain time, if it could be 
 seen at all. One of them (the Frenchman) felt so sure of 
 his ground that he wrote to a friend and said, "Look 
 there, and you will see it." That friend (Or. Galle of 
 Berlin) did look, as he was bid to do, and the very first 
 night that he turned his telescope to the spot, there he 
 found the Planet, close by the very place which had been 
 iixed for it. 
 
 The ancients knew only five of the large Planets in the 
 Table, namely, Mercury, Venus, Mars, Jupiter; and 
 Saturn. They did not know that the Earth was a 
 Planet at all. They thought that it was fixed, and that 
 
FIRST LESSONS IN SCIENCE. 51 
 
 the Sun and Moon went round it. So they joined these 
 two with the five, and said there were seven Planets. 
 
 6. Thus the Earth is one of a large company, which 
 wait, as it were, upon their lord the Sun. He resides in 
 the middle of his court, and makes them all go circling 
 round him, each in its own proper path and in its own 
 proper time. Hence these are not, like the Fixed Stars, 
 fixed in the sky, seeming only to rise and set, because the 
 Earth turns round on its axis, but really not moving, and 
 always seeming to rise and set in the same points of the 
 sky. But the Planets move about in the sky with their 
 own proper motion. Like the others, they seem to rise 
 and set. But they change from day to day their places 
 of rising and setting. They have motions of their own, 
 and are seen wandering as it were about the sky — though 
 none of the greater planets go out of a certain belt of the 
 sky, called the Zodiac — and hence they have got the name 
 of Planets, that is, Wanderers. The ancients, indeed, 
 thought that they wandered about wildly, as in fact they 
 seem at first sight to do. For sometimes they appear to 
 go forward, sometimes backward, sometimes more quickly, 
 sometimes more slowly, and sometimes they appear to 
 stop still. Mercury and Venus, it is true, are kept within 
 their tether, as it were, and must stay near the Sun. But 
 the others are found roving, as it were, " at their own 
 sweet will," Sometimes they are seen in the same part 
 of the sky as the Sun, and then they will appear smaller. 
 At other times they are seen in the opposite part of the 
 sky to that in which the Sun is, and they will seem 
 larger. 
 
 7. The ancients could not explain these motions. They 
 tried all sorts of schemes to account for them. But, as 
 they would insist upon putting the Earth as the centre, 
 about which all the others were to move, they never 
 
 M 2 
 
52 FIKST LESSONS IN SCIENCE. 
 
 could see the reason of all the facts which they obserred. 
 There was a famous ancient, Pythagoras (about B.C. 500) 
 who put forward the true notion of the Earth going round 
 the Sun. But the people of those days would not listen 
 to him. They had not the means for knowing the truth 
 which we have now. They had no telescopes, and there- 
 fore no such perfect knowledge of the heavens as we have. 
 So another great philosopher, Aristotle, opposed the views 
 of Pythagoras, and they were set aside entirely for nearly 
 2000 years. Ptolemy, an Egyptian astronomer of Alex- 
 andria, who lived about a.d. 150, wrote a book to explain 
 the motions of the heavenly bodies, on the notion that 
 the Sun, and Moon, and Planets, all went round the 
 Earth, with a curious arrangement of their orbits. His 
 was a very complex system. It answered just for a little 
 while, and then all went wrong again. The Planets got 
 all out of their places, and new schemes were devised in 
 order to keep them right. 
 
 8. Nothing, however, availed, till at last in a.d. 1543, a 
 Prussian clergyman named Copernicus, who was a great 
 astronomer, brought forward again the system of Pytha- 
 goras, and boldly asserted that the Sun was the centre of 
 the system, and the Earth and other Planets went round 
 him. He did not see, however, that they went round in 
 simple circular orbits. Even yet there were no tele- 
 scopes, and no such clear knowledge of the motions of the 
 heavenly bodies as now any child may possess. But what 
 he did publish to the world had been the result of many 
 years of profound study, and of a multitude of observa- 
 tions. These he had made with the rude means at his 
 command in the little town where he lived amidst the 
 marshes, where he was, however, often hindered in his 
 work by the damp steaming fogs that rose from the river 
 Vistula and a lake hard by. For thirty-six years had he 
 
FIRST LESSONS IN SCIENCE. 53 
 
 thus been engaged, and tiien at last, when he had proofs 
 enough of the truth of what he said to convince his own 
 mind, and perhaps, as he hoped, to convince others, he 
 published his book, being now quite an old man, in his 
 seventy-second year. The first printed copy was put into 
 his hands a few hours only before he died. So he never 
 saw the effect which it produced upon the minds of men, 
 and the mighty change which in due time it wrought in 
 their views, not only with regard to the motion of the 
 Earth, but at length with regard to the whole vast 
 Universe. By this system of Copernicus all the seem- 
 ingly wild movements of the Planets are brought into 
 perfect order, as soon as we know that they are all going 
 round the Sun in the centre, and that the Earth also 
 among them is going round him, and so we see them 
 moving while we are moving also. It can be easily 
 shown, as I will show you farther on, that this is quite 
 enough to cause all those strange appearances of forward 
 and backward motion, or sometimes of stopping still. 
 
 9. But why did I say that the Sun lords it, as it were, 
 over his troop of Planets, and makes them go round him ? 
 You will partly see why if you will think of what takes 
 place when you are swinging round a stone fastened to 
 the end of a string, the other end being held in your 
 hand. The stone, you know, will go round in a circle. 
 But why ? Because of two things ; because it has a 
 forward motion of its own, which you have given it, and 
 because also the string is held in your hand, and you feel 
 the stone pull upon you, trying to get away, and you 
 resist that pull and hold it fast. If you did not do so it 
 would fly off at once in the direction in which it was 
 moving at the moment you let the string go. Observe, 
 then, that two things are needed in order that the stone 
 should go round in this way. It must have a forward 
 
54 FIRST LESSONS IN SCIENCE. 
 
 motion of its own given to it, and it must also be held 
 back by the conBtant pull of the hand. Now this is just 
 what takes place when the Earth, or any other Planet, 
 goes round the Sun. The Great Creator, when He first, 
 by His Almighty Word, launched forth, as it were, the 
 ball of the Earth into the regions of space, gave it a forward 
 motion of its own. And, with this motion only, it would 
 have gone forward in a straight line in the same direction 
 for ever and ever, unless it came across some other body, 
 or was stopped in some other way by the same Almighty 
 Word which set it first in motion. But, besides this 
 forward motion of its own, there is the huge body of the 
 Sun attracting, the Earth, pulling it constantly towards 
 itself, like the pull of the hand upon the stone. And this 
 pulling power is just exactly strong enough to bend the 
 Earth's path from the straight line in which it would 
 have gone on into the curved path which it is forced to 
 take. So these two things together — the Earth's own 
 forward motion given to it at first, which it still retains, 
 and the Sun's attracting power — are the causes of the 
 Earth's going round the Sun in a circle. 
 
 10. And the same thing, of course, may be said of any 
 other of the Planets. Strictly speaking, it is true the 
 paths of the Earth and Planets are not exactly circles. 
 But they are so nearly so that, for the present at all 
 events, we may speak of them as such. And all the 
 chief Planets go round nearly in the same plane as that 
 in which the Earth goes round, and which is called the 
 Ecliptic ; so that by the help of what you have read in 
 (4) you may draw all the circles on a flat piece of paper. 
 Thus take any small radius to represent Mercury's dis- 
 tance from the Sun (37 millions of miles), and draw his 
 orbit. Then stretch out Mercury's radius till the increase 
 makes it to be nearly as long again (69 millions of miles), 
 
FIRST LESSONS IN SCIENCE. 55 
 
 and so you will get at Venus's radius. Stretch, oiit this 
 till the increase is double the former increase, and this 
 will give us the Earth's distance. Stretch, out the Earth's 
 radius till the increase is double the last increase, and 
 this will give us Mars's distance. And so on, the next 
 step giving us the place of the Planetoids, the next that 
 of Jupiter, the next of Saturn, the next of Neptune. And 
 thus we shall have an idea of the orbits in which the 
 Planets of the Sun's troop, or the Solar System, as it is 
 called, are moving constantly round him. And they all 
 go round in the same direction, which direction, as seen 
 from the North side of the Ecliptic, is from the right 
 hand of a man in front of him towards his left, or 
 opposite to that in which the hands of a watch go. 
 
 11, Outside the orbit of Neptune, as far off as your 
 paper will allow, you may draw a circle to represent the 
 region of the nearest Fixed Stars. And yet this distance, 
 however large may be the border left upon your paper for 
 it, will be vastly too small. Eor Neptune's distance from 
 the Sun is about 3000 millions of miles, and that of the 
 nearest Fixed Star, as we know, is 20,000,000 millions of 
 miles, that is, it is nearly 7000 times as great as Neptune's 
 distance. You see then what an awful vacancy surrounds 
 on every side the Sun and his little family. There may 
 be a distant Planet or two yet to be found, circling out- 
 side the orbit of Neptune. But in all the vast space 
 around us on all sides, for 7000 times the distance of 
 Neptune from the Sun, there is, as I have said, an awful 
 void. We are all alone by ourselves, as it were, in the 
 vast Universe. But each twinkling point of light that 
 we see, even each one of those which are scattered by 
 millions in the sky, like glittering dust in that long trail 
 of light, which is called the Milky Way, is a Sun like 
 ours, with his family of Planets also, all by himself in 
 
56 FIRST LESSONS IN SCIENCE. 
 
 space, separated by the like vast interval from fill other 
 Stars. 
 
 12. Thus, then, as I have said, the whole Earth, with 
 all the people and things upon it, is not only spinning 
 round upon its axis once in 24 hours, hut going round the 
 Sun in its orbit once in 365 days. And yet we are not 
 conscious of the motion in either case. We are carried 
 along with the Earth, and the motion is so steady, that 
 like the fly, of which we spoke before, when the waggon is 
 turned, we do not at aU. perceive it. The air which sur- 
 rounds us, and which we breathe, goes round, as we do, 
 with the Earth, as if it were a part of it. If it did not, 
 we should feel it as a constant mighty wind of fearful 
 violence, more terrible than any of which we can con- 
 ceive. For let us see at what rate we are really moving. 
 Our motion is made up of two— one, which we have, 
 because the Earth is spinning round on its axis, and 
 another which we have, because the Earth is going round 
 the Sun in its orbit. Now the motion which a man has 
 from the former cause will not be the same at all parts of 
 the Earth. If, for instance, he could stand with his feet 
 upon the Pole itself, he would not move at all as the 
 Earth went round, except just to be turned round in his 
 place, as he stands, once in 24 hours. If, again, he stands 
 on any part of the Equator, he will be carried round, as 
 the Earth goes round, through a length equal to the whole 
 circumference of the Earth at the Equator, which we 
 know to be 25,000 miles, once in 24 hours, that is, he will 
 be carried round at the rate of more than 1000 miles an 
 hour. If he stands anywhere between the Pole and the 
 Equator, he will be carried round at some rate less than 
 this, but faster and faster as he gets nearer to the 
 Equator. 
 
 13. But let us now look at the motion which a man has 
 
FIRST LESSONS IN SCIENCE. 57 
 
 because of the Earth's motion round tlie Sun in its orbit, 
 ■which is the same for all of us in all parts of the Earth. 
 Since the Earth's distance from the Sun, that is, the radius 
 of its orbit, is 96 millions of miles, the diameter of its 
 orbit will be twice this, or 192 millions of miles, and its 
 circumference will be three and one-seventh times this 
 latter number, that is, it will be about 600 millions of 
 miles. This, then, is the distance through which we are 
 all carried with the Earth, every year, through the vast 
 regions of space. And if we divide this by 365 we shall 
 get the distance through which we are carried in a single 
 day, about 1,644,000 miles ; and, dividing this by 24, we 
 find the rate at which we go in an hour to be about 68,000 
 miles, or more than 1000 miles a minute. Now a gentle 
 pleasant breeze blows at the rate of about 4 miles an 
 hour, a strong wind at the rate of 35 or 40 miles an hour, 
 a storm at the rate of 60 miles, and the most terrific 
 hurricane at the rate of 100 miles an hour. Here are we 
 moving, every one of us, at the rate of 1000 miles in a 
 minute, and we do not feel, on account of this motion, so 
 much as a breath of air on our faces. This shows that the 
 air must be moving with us. If it were not so — if we 
 only, and the Earth, and the things on it, were moving, 
 while the air was standing still — we should be torn to 
 pieces in an instant, by being carried violently against it, 
 with a force six or seven hundred times as great as that 
 with which we may have felt the air strike us in the most 
 tremendous storm. There are certain winds, however, 
 called the trade winds, which do partly arise from the 
 Earth's turning round upon its axis. I will explain how 
 this happens farther on in this book. 
 
 14. It is easy to find the rate at which any one of the 
 other Planets goes round the Sun by doubling its distance 
 from the Sun, and then taking three and one-seventh 
 
58 FIEST LESSONS IN SCIENCE. 
 
 times the distance so found, by which we obtain the 
 length of its orbit. Then dividing this by the number of 
 days in its Year, we find the number of miles it travels in 
 a day. In this way we should find that Mercury's rate 
 per day is about 2642 thousands of miles, or 110,000 miles 
 per hour, so that he moves nearly twice as fast as the 
 Earth, whereas Neptune's rate per day is about 300 
 thousands of miles, or only 12,000 miles per hour, about 
 one-fifth of the rate at which the Earth moves. And so 
 it would' be found that those which are nearest to the 
 Sun go quicker than those which are farther off; as, of 
 course, they must do, in order not to fall into the Sun, 
 drawn, as they are, by his mighty attraction, which those 
 that are nearest to him feel the most. 
 
 All the Planets also, it is believed, and the Sun and 
 Moon also, turn round, as the Earth does, upon their axis, 
 and turn, as she does, from West to East. I say, it is 
 believed that they all do so, because it can be seen that the 
 Sun and Moon and most of the Planets do so. But the 
 Planetoids are too small, and Mercury is too near the Sun, 
 and Venus looks very hazy, as if wrapped in a cloudy, 
 misty covering, so that these cannot be seen distinctly to 
 be turning round. However, there is little doubt that 
 they do, as the rest do. 
 
 15. Now let us see one or two things which will follow 
 from the fact that the Earth has this double motion, 
 namely, that of going round the Sun in her orbit, and 
 that of spinning round as she goes. But, first, it will be 
 well that you should know the meaning of one or two 
 terms which are often used in speaking of such matters as 
 these. So let us draw a circle to represent the Earth's 
 orbit, and put the letter S for the Sun in its centre. And 
 let us mark four points with the letters A, B, C, B, at 
 equal distances in the orbit, to represent the Earth's place, 
 
TofOAX page 59. 
 
FIRST LESSONS IN SCIENCE. 59 
 
 as she goes round the Sun at four different parts of the 
 year, at intervals of three months, as in Spring, Summer, 
 Autumn, and "Winter. Draw the two diameters AC, BD, 
 which will, of course, divide the whole circle, as well as 
 its circumference, into four equal parts. 
 
 Now the amount of opening between two lines, which 
 meet each other, is called an angle. Thus the opening 
 ASB, between AS and BS, is an angle ; so is the opening 
 BSO, or GSD, or ASD. Observe, I do not mean the space 
 ASB, which is a quarter of the whole circle, and is called 
 a quadrant, but only the opening between the two lines, 
 which would remain just the same if the lines were 
 lengthened out beyond A and B to be each a thousand 
 miles long, or if they were shortened to be each only a 
 thousandth part of an inch long, or if one were lengthened 
 and the other shortened. It will make no difference at 
 all in the size of the angle ASB if we alter in any way 
 the length of the two lines which contain it, and if we 
 alter either one or both of them. The angle would only 
 be altered by making the opening greater or less between 
 the two lines. Thus, if between the radii SA and SB we 
 draw another radius SE, then the angle ASB is different 
 from the angle ASB, and is plainly less than it, while the 
 angle CSE is plainly greater than the angle CSB. 
 
 16. Now the angles ASB, BSG, CSD, DSA, are all equal 
 to one another ; and whenever this is the case, that two 
 straight lines, like AC, BD, cross one another so as to 
 make equal angles at the point where ihey meet, these 
 angles are called right angles, and one of the two lines is 
 said to be at right angles or perpendicular to the other, that 
 is, AG is perpendicular to BD, and BD to AG, and if a 
 line be drawn from any point in a flat piece of paper (as, 
 for instance, the point S in this figure), so as to project 
 from the face, of the paper, and be at right angles to every 
 
60 FIKST LESSONS IN SCIENCE. 
 
 straight line in the paper that meets it (as, in this case, 
 SA, SB, SC, and SD), such a line is said to be at right 
 angles, or perpendicular, to the plane, or flat surface, of 
 the paper. On the other hand, if two lines are drawn in 
 the same direction, so that, when produced ever so far, 
 they will never meet, they are said to be parallel to one 
 another. And a line is parallel to a plane when it never 
 meets it, however far it may be produced. In like 
 manner, one plane may be parallel or perpendicular to 
 another. 
 
 17. Again, it is usual to divide the whole circumference 
 of a circle into 360 equal parts, called degrees ; so that 
 each quarter of the circumference, as AB, will contain 90 
 of these degrees, which is denoted thus, 90°. So also BO, 
 CD, DA, contain each 90°. 
 
 Any piece of a curved line is called an arc (from arms, 
 a bow). Hence AB is an arc, and BG, CD, DA, are all 
 arcs. So AE is an arc ; and if E be the mid-point of AB, 
 then the arc AE will contain half of 90°, that is, 45°. So, 
 too, BE will contain 4.5°, and CE will contain 135°. Or 
 if AE be the third part of AB, then it will contain only 
 30° ; if AEhe the fourth, fifth, or sixth part of AB, it will 
 contain 22^°, 18°, or 15°. 
 
 If we take AE such that its length shall be exactly 
 equal to the length of the radius SA, then it i^ found that 
 AE will be nearly two-thirds of AB, and will, in fact, 
 contain about 57i°. 
 
 18. But now it is very plain that the angle ASE will be 
 just the same part of the angle ASB that the are AE is of 
 the arc AB. If AE be the half, third, or fourth of AB, 
 then the angle ASE will be the half, third, or fourth of 
 the angle ASB. Hence it has been agreed to divide the 
 right angle ASB into 90 equal angles, and to call them by 
 the same name, degrees. So that each of the angles ASB, 
 
FIRST LESSONS IN SCIENCE. 61 
 
 BSC, &c., contains 90°, and the whole four of them con- 
 tain together 360° ; and if tlie arc All he the half, third, 
 fourth, &c., of the arc AB, then the angle ASE will be 
 the half, third, fourth, &c., of the angle ASB, and will 
 contain 45°, 30°, 221°, &c. So, too, if AE be equal in 
 length to the radius of the circle, and therefore, as above 
 stated, contains 57^°, the angle ASE, which is opposite to 
 AE, or subtends it at the centre of the circle, will also 
 contain 57J°. 
 
 19. This relation between the angle at the centre of a 
 circle and the arc of the circumference which subtends it 
 is expressed by saying that, in the same circle, an angle 
 at the centre is proportional to the arc which subtends it, 
 or by saying that two angles at the centre of a circle 
 have the same ratio, or Jtave the same proportion to one another, 
 as the arcs which subtend them, or by saying that one of 
 the two angles has the same ratio to the other as the arc 
 which subtends the first angle has to the arc which sub- 
 tends the second. So the price of a quantity of sugar is 
 proportional to the weight, a man's wages is proportional 
 to the number of days he works, &c. By such an expres- 
 sion in all oases it is meant that if one of the two things 
 which are proportional to one another be doubled, halved, 
 &o., then the other will also have to be doubled, 
 halved, &-c. 
 
 20. But astronomers are obliged to be very careful in 
 their calculations, and to notice much smaller angles than 
 degrees. So they have agreed to divide each degree, 
 whether of arc or angle, into 60 smaller divisions called 
 minutes, and each minute into 60 smaller still, called 
 seconds ; and they denote minutes by (') and seconds by 
 ("). Thus, instead of 22J°, as above, they may write 
 22° 30' ; and an arc or angle containing 57 degrees, 17 
 minutes, 45 seconds, would be written down 67° 17' 45". 
 
62 FIRST LESSONS IN SCIENCE, 
 
 This is the more exact size of tlie arc, wMcli in any circle 
 whatever is equal in length to the radius of the circle 
 (and which was stated above to he about 57^°, or 57° 15'), 
 and therefore, also, it is the size of the angle which sub- 
 tends such an arc at the centre of the circle. And you 
 must note that the actual length of the arc in this case 
 will vary according to the size of the circle or its radius. 
 But the size of the angle of 57° 17' 45" remains the same 
 whatever may be the length of the lines containing it, 
 and whatever may be the size of the circle. 
 
 21 . And now let us return to the Earth and her motions, 
 and the effects which follow from them. And first let me 
 explain, as I promised in (8), the reason of the strange 
 movements of the Planets, as they appear to our eyes, 
 sometimes going forward, sometimes going backward or 
 retrograding, and sometimes standing still. Let us take, 
 as an- example, the case of Jupiter. Now you will see by 
 the Table in (2) that the radius of Jupiter's orbit, that is, 
 his distance from the Sun, is about five times that of the 
 Earth's orbit. Draw two circles about the same centre, 
 so that the radius of one shall be five times that of the 
 other. Let the outer circle represent Jupiter's orbit, and 
 the inner circle the Earth's ; and put S in the centre to 
 represent the Sun, Draw a radius SEJ, cutting the 
 Earth's orbit in E and Jupiter's in J ; and suppose that, 
 at some one moment, as they are going round in their 
 orbits about the Sun (in the opposite direction to that in 
 which the bands of a watch move), the Earth is at E and 
 Jupiter at J. 
 
 22. Now Jupiter goes round the Sun in 4333 days, and 
 the Earth in 365 days ; that is, Jupiter takes about twelve 
 times as long to go round the Sun as the Earth does. 
 Hence, while the Earth goes through a quarter of her 
 orbit, Jupiter will only go through about a twelfth part 
 
Tofaaepage^i. 
 
FIRST LESSONS IN SCIENCE. 63 
 
 of a quarter of his. Divide the orbits into quarters by 
 two lines through S, crossing each other, one of them 
 being JUS produced. Put letters F, G, H, at the ends of 
 the quarters of the Earth's orbit; and divide the first 
 quarter of Jupiter's orbit (the quarter next to J, through 
 which the Planet will first move) into twelve equal parts ; 
 and put letters K, L, M, at the ends of the first three of 
 them. Then when the Earth is at E and Jupiter at J, 
 Jupiter will be seen from the Earth in the direction EJ 
 produced, far away among the Stars. When the Earth, 
 gets to F, Jupiter will have got to K, and will therefore 
 be seen from the Earth in the direction FK produced, 
 that is, it will seem to have gone bachward. When the 
 Earth gets to 0, Jupiter will have got to L, and will be 
 seen in the direction OL produced, so that it will now 
 seem to have gone forward, and somewhere between the 
 last two points of 7)bservation there will be a point where 
 Jupiter, as seen ftom the Earth, will seem neither to go 
 backward or forward, but to be stationary for a time. 
 When the Earth gets to S, Jupiter will be seen in the 
 direction jBTil/ produced, and will still seem to have gone 
 forward. 
 
 23. Next let us suppose a person standing, on a clear 
 evening, in any part of the world, in a wide plain, or in 
 a ship out at sea, and looking up at the Stars. Now, first, 
 it is plaia that he will not see at any one moment all the 
 Stars that are in the whole firmament — I mean, all those 
 which can be seen in all parts of the world by men's eyes. 
 He will only, at most, see about half of them, those which 
 at that moment happen to be in the sky over his head, 
 for his view will be bounded by the circular line of which 
 we spoke before, whose proper name is the horizon, or 
 bounding line. The great body of the Earth beneath his 
 feet will hide from his sight the other half of them, those 
 
64 FIRST LESSONS IN SCIENCE. 
 
 whioli are below his horizon. But then, as the Earth 
 turns round from West to East, some of the Stars which 
 he saw at first will be hidden from his sight, and seem to 
 go down in the. West and disappear, and others will 
 appear in the East. And this will be going on all night 
 and all day too ; though, when the Sun rises, the glare of 
 his light will prevent the Stars from being seen with the 
 naked eye. Venus, indeed, and even Jupiter, can often be 
 seen in broad daylight by one who knows where to look 
 for them. But all the brighter stars, and many of fainter 
 lustre, can be seen by day through a good telescope, so 
 contrived that no sunlight, if possible — no light but that 
 of the Star to which it is pointed — may pass down the 
 tube to the eye of the observer. And bright Stars may 
 be seen by day from the bottom of a deep well, or tall 
 chimney, or the shaft of a mine. 
 
 24. But now comes a question. "Supposing that a 
 man stood during the whole 24 hours so as to see all 
 the Stars which would thus be brought into view at the 
 place where he stands, by day and by night, would such 
 a person see all the Stars — all that can be seen by man on 
 Earth — all that are within reach of the human eye ?" 
 
 Yes, if he were standing at some point of the Equator : but 
 not otherwise. If he were standing in the Equator, with 
 his face towards the East, he would have the North point 
 on his left hand, and the South point on his right hand ; 
 and, one after another, all the Stars in the whole heaven 
 would be seen by him, rising at different points afl. along 
 the whole line ,of the horizon in front of him, from the 
 North point on his left to the South point on his right. 
 And, as the Earth turned round towards the East, these 
 would all seem to move towards the West, describing 
 half-circles — those most nearly right in front of him 
 describing large circles, which go right up over his head 
 
FIRST LESSONS IN SCIENCE. 65 
 
 — those more towards the left or right describing smaller 
 circles, looking smaller and smaller as they rose more near 
 to the North or South point. All the Stars, which rose 
 at any moment, he would see taking just twelve hours to 
 describe their half-circles, whether large or small, and so 
 they would set and disappear ; and in the course of the 
 twenty-four hours all the Stars in the whole visible 
 Heavens would thus be brought under his view. All 
 this, it is plain, arises from the Earth turning round upon 
 its axis, which lies in the direction North and South 
 with the Poles in his horizon. If we suppose the Earth's 
 axis lengthened out beyond the Poles on both sides, to 
 reach the Starry Heavens, the points in which it will 
 seem to meet it will be called the North and South Poles 
 of the Heavens. 
 
 25. Now let us suppose the man to stand upon one of 
 the Poles of the Earth, say the North Pole. As before, at 
 any one moment, he would see only half the Stars in 
 the firmament, the rest being hidden from him by the body 
 of the Earth under his feet. But now, as the Earth turns 
 round, no more Stars will come into view. The Stars 
 which he saw at first will seem to go round him in circles, 
 never rising or setting, but always remaining at the same 
 distance from the horizon. Those directly over his head 
 will be describing very small circles, those near the hori- 
 zon very large ones ; but all will complete their circles 
 in the same time, namely, that in which the Earth goes 
 round on its axis. The Earth's axis is now right under his 
 feet ; and the North Pole of the Heavens is over his head. 
 
 26. Lastly, suppose the man to stand in some other 
 part of the Earth, and to watch carefully the motions of 
 the Stars — the motion, that is, which they seem to have 
 from East to West, because of the Earth going round 
 upon her axis in the opposite direction from West to East. 
 
bb FIRST LESSONS IN SCIENCE. 
 
 What new will he behold ? We shall see ■ this best, 
 perhaps, if we suppose the Earth really to stand still, and 
 the starry vault really to go round, as it seems to do, upon 
 its axis, that is, upon the line which joins the North and 
 South Poles of the Heavens. Wherever the man is, one 
 of these Poles will now be somewhere above his horizon. 
 There may be no Star to mark exactly its place in the sky, 
 though, indeed, there is a Star, very near the North Pole 
 of the Heavens, known as the Pole-star, which serves to 
 point out its place. But there such a pole is, tke point 
 where the axis of the Earth produced seems to meet the 
 starry vault. And in the' sky on the opposite side of the 
 Earth is another such Pole. And the axis, about which 
 the hollow sphere of the Heavens turns, is the line which 
 passes along the Earth's axis from one of these Poles to 
 the other. Now, as the Starry Heavens revolve about this 
 axis, the observer will see those Stars which are nearest to 
 the Pole circling about it continually, never rising or 
 setting, but going through the whole daily circles in his 
 sight. At last, there may be seen a Star, far enough from 
 the Pole for its circle to be so large that it just grazes the 
 horizon on one side of him, either to the North or South, 
 . as the North or South Pole is that which is seen by him. 
 And all the Stars which are farther off from the Pole than 
 this will ri^e and set, only describing portions of their 
 circles in his sight, these portions getting smaller as the 
 Stars are farther from the Pole. 
 
 27. Now let us look again at the figure which we drew 
 in (15), where the letters A, B, C, D, represent four 
 places of the Earth going round the Sun in her orbit, the 
 Ecliptic (in the direction opposite to that in which the 
 hands of a watch move), at the four quarters of the year. 
 Draw, as in (11), a circle of stars far outside the Earth's 
 orbit, to represent the region of the Fixed Stars. Then, 
 
FIRST LESSONS IN SCIENCE. 67 
 
 when tite Eartli is at A, it will be dark, of course, on that 
 side of the Earth which is turned away from the Sun ; 
 and, therefore, at midnight, a person will be able to see 
 only those stars which lie in that part of the Starry 
 Heavens which is on the side of BAD. Those about B 
 will be beginning to set to him, as he is being turned 
 away from them by the spinning motion of the Earth. 
 Those about B will be beginning to rise to him, as he is 
 being turned towards them. Those about A will be seen 
 the whole night long, and are now, at midnight, midway 
 between rising and setting. This, of course, is only true 
 of those Stars which do rise and set to him. The Stars 
 which circle around the Pole and never rise or set to him, 
 will be seen by him through that half of their course 
 which is on the same side of the Pole as A is from S. The 
 other part of their course they will perform in the day- 
 time, when he cannot see them.' 
 
 So again, three months after this, when the Earth will 
 have reached B, he will see at midnight the Stars on the 
 side of ABC ; and when the Earth has got to C, he will 
 see at midnight those on the side of BGB. Those, which 
 he saw when at A are now only to be seen, if seen at all, 
 in broad daylight, because, when he is turned towards 
 them, he is turned also towards the Sun. Except, of 
 course, the circumsolar Stars (those which circle about the 
 Pole), which he will still see the same as at A ; only now 
 he will see them in that half of their course which he 
 could not see when at A, 
 
 28. If we could imagine the Stars to be seen while the 
 Sun is shining, or if we could look through one of the best 
 telescopes we should always see him, from the earth, sur- 
 rounded by Stars, as the Moon is at night, and seeming to 
 be moving among them, by reason of the Earth moving 
 round in her orbit. Thus, when the Earth is at A, the 
 
 F 2 
 
68 FIEST LESSONS IN SCIENCE. 
 
 Sun will seem to lie among the Stars beyond C. He is 
 really not among them, for they are at a vast distance 
 beyond him. But it would look so to our eyes ; just as 
 the Moon seems to be moving about among the Stars, 
 though they are so far beyond her. Now the Stars, 
 through which the Sun seems thus to travel from one end 
 of the year to the other, have been, in ages long ago, by 
 old Hindoos and Egyptians, formed into groups, to which 
 certain names have been given by the ancients, which 
 names are still retained. The name is given in each case 
 from some fancied likeness, in the arrangement of the 
 Stars of each group, to the figure which it expresses. 
 Such groups have been formed by men's fancies all over 
 the sky, and are called Constellations. They are useful 
 for pointing at once to the place of a Star, if we know 
 that it belongs to any particular part of such a group. 
 Thus there is a famous group of Stars near the North Pole 
 which form the figure of a Great Bear ; and in the South- 
 ern regions of the sky there is another bright constella- 
 tion, making the figure of the Southern Cross. And 
 it is convenient to refer to a Star, as being in the 
 tail of the Great Bear, or in the foot of the Southern 
 Cross, &c. / 
 
 29. These groups, through which the Sun seems to 
 travel, have mostly the figures of animals, and are called 
 the Constellations of the Zodiac — this word Zodiac (from a 
 Greek word, zodion, animal), being the name given to a 
 narrow belt of the sky, within which the Sun, Moon, and 
 larger Planets, all appear to move. The Constellations of 
 the Zodiac are twelve in number, and each is supposed to 
 fill an equal length of the sky, so that the Sun takes 
 about 30J days in passing through each of them. The 
 names of these Constellations in Latin and English are as 
 follows : — 
 
FIRST LESSONS IN SCIENCE. 69 
 
 Aries, the Earn. 
 Taurus, the Bull. 
 Gemini, the Twins. 
 Cancer, the Crab. 
 Leo, the Lion. 
 Virgo, the Virgin. 
 
 Libra, the Balance:' 
 Scorpio, the Scorpion. 
 Sagittarius, the Archer. 
 Capricornus, the Goat. 
 Aquarius, the Water-bearer. 
 Pisces, the Fishes. 
 
 30. Next let us see how we may account for those 
 changes, which we observe in the length of the day and 
 night, at different parts of the year, and for those which 
 take place in the seasons. 
 
 Consider, first, that if the Earth's axis were kept always 
 perpendicular to the plane of the Ecliptic, as she went 
 round the Sun in her orfeit, there would be no such 
 changes at all. For, by her turning round on her axis, 
 every place on her surface would be brought under the 
 Sun's rays for twelve hours, and turned away into the 
 darkness for twelve hours; and so there would be no 
 difference in the length of the day and night all the 
 world over, and no difference in the seasons. Only the 
 places upon the Equator would be much hotter than those 
 near the Poles, for every part of the Equator would be 
 brought, as the Earth turns round, not only under the 
 Sun's rays, but directly under them. The Sun's rays at 
 noon would fall right down upon the heads of people 
 living on the Equator. Whereas, nearer the Poles they 
 would reach the surface of the Earth in a slanting direc- 
 tion, even at mid-day, just as they would do at the Equator 
 about sunrise or sunset. Hence the Earth about the Poles 
 would not take in so much of the heat as at the Equator, 
 and would not be so thoroughly warmed ; so that it would 
 be always intensely hot near the Equator, but cooler and 
 cooler towards the Poles. And, as I have said, there 
 would be no difference in the length of the day anywhere 
 throughout the Earth. 
 
 31. But God has ordered otherwise in his Goodness and 
 
70 FIRST LESSONS IN SCIENCE, 
 
 Wisdom. He has set the Earth's axis not perpendicular 
 to the plain of the Ecliptic, but sloping towards it. And 
 he has bid the Earth go round the Sun, with its axis 
 always pointing in the same direction, or parallel to itself. 
 And so, by making it turn about such an axis as this, He 
 has provided that all these changes shall be produced, 
 which minister so much to our welfare and happiness, 
 Let me show you how this is brought about. 
 
 Suppose, then, the Northern end of the Earth's axis, 
 which before we had placed perpendicular to the plane of 
 the Ecliptic, to be pulled over towards the Sun, through 
 an angle of 23° 28', that is, through about one-fourth of a 
 right angle ; by which, of course, the Southern end will 
 be moved away from the Sun through the same angle. 
 This is the position which the axis of the Earth has about 
 June 21. It is now inclined to the plane of the Ecliptic 
 and it will keep the same position as regards that plane 
 (though not, of course, as regards the Sun), remaining 
 always parallel to itself, while the Earth goes round the 
 Sun in its orbit. 
 
 32. Such, then, is the axis, inclined thus to the plane of 
 the Ecliptic, about which the Earth is daily turning. 
 Now, as it turns round, with one half bright with the 
 Sun's rays, and the other half turned away from the Sun, 
 and shaded in darkness, you will see that the parts about 
 the North Pole, which is turned towards the Sun, are 
 never turned away from the Sun's rays into the darkness, 
 though they turn round the Pole as the Earth turns round. 
 At this time of the year, then, there is constant daylight 
 to all these parts of the Earth. There is no night ; but 
 the Sun seems only to describe a circle in the sky during 
 the 24 hours. He will be at the lowest point of the circle 
 at that time, which corresponds to midnight in other parts 
 of the Earth ; and he will mount up higher and higher, 
 
FIEST LESSONS IN SCIENCE. 71 
 
 till at midday he will get to Hs highest point, and then 
 dip down till he reaches the lowest point again, without 
 ever setting. But, though there is constant daylight in 
 these parts at this season of the year, yet the Sun's rays 
 fall very slanting, and do not supply much heat. 
 
 33. Now, if you will look at the other Pole, the South 
 Pole, you will see that it is turned away from the Sun, as I 
 have said, and forms a portion of the dark side of the 
 Earth ; and all the parts near it never come out of the 
 darkness, though they go round the Pole as the Earth goes 
 round on its axis. While, then, the Northern polar regions 
 are having day without night, the Southern polar regions 
 are having night without day. The people who live there 
 see no Sun rise or set at this season. Only the Moon and 
 the Stars light up their darkness with brilliant flashes of 
 splendid light, called the Aurora, which streams quivering 
 up the sky at times in ceaseless glimmerings. And this 
 state of things will continue at any place near the South 
 Pole, till the Earth has gone on far enough in its orbit 
 round the Sun, for the position of the place to be so 
 changed with respect to the Sun, that, as the Earth turns 
 round on its axis daily, the place will be brought out of 
 the darkness into the light of the Sun's rays. First, for 
 a few moments at noon, the Sun will just peep above the 
 horizon of such a place. And then, day after day, it will 
 rise earlier and set later, and so they will see more and more 
 of its daily circle, till at last they will see the whole of 
 it, and they will have passed out of perpetual night into 
 perpetual day, while the Northern Polar regions have now 
 passed in their turn out of their long day into as long a 
 night. This will be when the Earth has got to the oppo- 
 site part of her orbit around the Sun, about December 21. 
 And you will see that the South Pole will now be turned 
 towards the Sun, and the North Pole turned away from it. 
 
72 FIRST LESSONS IN SCIENCE. 
 
 '34. At the Poles themselves, there will be six months 
 of contimial daylight, and six months of contimial dark- 
 ness during the year. At any other place in the Polar 
 regions, the time, during which there is constant day, 
 will be longer according as the place is nearer to the 
 Pole ; and the time of constant night will always be the 
 same as that of constant day. So that in some places the 
 Sun is wholly lost to view for four months at a time, in 
 others for two months, in others only for a month, or a 
 week, or even for a single day only, if the place happens 
 to be just on the edge of the polar regions. These regions 
 about the North Pole are called the Arctic Kegions, from 
 the Greek word Arctos, for Bear ; because, as you have 
 been told, the constellation of the Great Bear (and another 
 also, called the Little Bear), is very near the North Pole 
 of the Heavens. The opposite regions of the globe, about 
 the South Pole, are called the Antarctic Eegions. If 
 circles are drawn on the surface of a globe, passing 
 through the North and South Poles, the Polar regions 
 extend for arcs of 23° 28' along these circles in all direc- 
 tions from each Pole, this being, as you will remember, 
 the number of degrees in the angle, through which the 
 Earth's axis is pulled down from the direction perpendicu- 
 lar to the plane of the Ecliptic. And at that distance 
 from the Poles you will see drawn, on any globe or map, 
 two dotted lines, which are called the Arctic and Antarc- 
 tic Circles, and which mark off those regions, where, at 
 certain parts of the year, the Sun never rises or sets. 
 Hence, since these regions are so long at a time without 
 the Sun, and when they do come under his rays, receive 
 them in so slanting a direction, they are always very 
 cold indeed, and are for ever covered with ice and snow. 
 
 35. Now let us see what happens about June 21, at 
 other parts of the Earth's surface. All these, you will see, 
 
FIRST LESSONS IN SCIENCE. 73 
 
 as the Earth turns round, will pass daily out of light into 
 darkness, and out of darkness into light ; that is, the 
 people living in such regions will see the Sun rise and set 
 daily. Only the more Northern parts wiE remain in the 
 Sun's rays, as the Earth turns, for a longer time than the 
 Southern, and get more of daylight and warmth. The 
 Northern will get more light than darkness, more day 
 than night ; the Southern will get more night than day. 
 In other words, it will he Summer in the Northern half of 
 the globe, and the days will he long, and the nights short ; 
 while it will be winter in the Southern half of the globe, 
 where the days will be short and the nights long. Since 
 the Earth's axis has been pulled down towards the plane 
 of the Ecliptic through an angle of 23° 28', of course the 
 Equator will have been pulled down under that plane 
 through the same angle. And so you will see that, as the 
 Earth turns round on her axis, the Sun's rays strike full 
 upon the heads of all the people who live upon the Earth 
 in any place which is distant from the Equator by an arc 
 of 23° 28', measured along a circle passing through the 
 two Poles. Such points will lie in a circle ; and you will 
 see a dotted circle marked upon any globe, so as to be as 
 far North of the Equator as the Arctic Circle is distant 
 from the Pole. The Sun will be overhead, or vertical (from 
 the Latin vertex, the top of the head), at noon, at this time 
 of the year, to all people living in that circle ; and the 
 heat will be very intense, not only in this circle, but in 
 all the regions near it on both sides. 
 
 36. As the Earth goes round in her orbit about the Sun, 
 keeping her axis always parallel to itself, the Sun will 
 cease to be vertical to places in that circle, and will be 
 vertical to places farther South, till at last, at the end of 
 three months, about Sept. 21, he will be vertical to 
 places in the Equator. To us living on the Earth, it will 
 
74 FIEST LESSONS IN SCIENCE, 
 
 seem that the Sun himself has gone farther to the South ; 
 and each day he will rise and set more towards the South 
 "than he did the day hefore. "We shall see his place of 
 rising and setting on our horizon changing in this way 
 from day to day. As the Earth still goes on in her orbit, 
 for three months more, he will get to be vertical to places 
 on the other side of the Equator, seeming to go farther 
 and farther to the South, till at last, about Dec. 21, he 
 will be vertical to all places in a circle like the former, 
 drawn around the globe, at the same distance South of the 
 Equator, as the Arctic or Antarctic Circle is from the 
 Pole. You will see such a circle also marked with dotted 
 lines on any globe or map. Then, as the Earth still goes 
 on, the Sun will seem to move northward. He will never 
 get to be vertical to places South of the circle which has 
 just been spoken of. For a day or two, indeed, about Deo. 
 21st, he will seem to stand still in this respect, being ver- 
 tical at noon for some few days together to all places on 
 this circle. But then he will go on and_be vertical to 
 places North of this circle, farther and farther North, till 
 again, after three months, on March 21, he will be ver- 
 tical to places in the Equator, and seein, as it were, to 
 cioss it from the South to the North side. And so, as the 
 Earth goes on, the Sun will be vertical to places on the 
 North side of the Equator, more and more to the North, 
 till, after three months more, about June 21, he will be 
 vertical again to all places in the circle first spoken of. 
 He will get no further North than this ; but after seeming 
 to stop still in this resjiect for a few days, he will seem 
 again, as before, to go to the South. 
 
 37. Hence the time of the year, about June 21, or 
 December 21, is called the Solstice (that is the Sun's 
 standing-time), and the two dotted circles just spoken of 
 are called the Tropics (that is, circles of turning), because 
 
FIEST LESSONS IN SCIENCE. 75 
 
 the Sun seems to stop still for a while, and then to turn 
 towards the South or North, when he gets to be vertical 
 to the places in these circles. The Northern one is called 
 the Tropic of Cancer, because the Sun about June 21 is 
 seen moving through the Stars in the sign of Cancer ; 
 and the Southern one, for a like reason, is called the 
 Tropic of Capricorn. It is plain that to all parts of the 
 Earth's surface, which lie between the two Tropics, the 
 Sun is vertical during some part of the year. The places 
 which are just on the two circles, pass under his hot direct 
 rays only once ; and the sun is then overhead at Noon 
 for a few days together. But to all other places between 
 the Tropics the Sun is vertical twice every year, once 
 when he is going towards the nearest Tropic, and again 
 when he comes away from it — that is, of course, when he 
 seems to go towards or come away. Hence such countries 
 are much more heated than the other countries beyond 
 the Tropics towards the North or South, to which the 
 Sun is never vertical. They are called tropical countries, 
 and are best suited for producing sugar, cotton, coffee, 
 indigo, &c., and all those plants which require much 
 heat. 
 
 38. The whole of the hot region of which we have just 
 been speaking, is called the Torrid Zone, that is, the 
 Scorched Belt, of the Earth's surface. The two tracts, 
 between the Tropics and the Polar Circles, are called the 
 Temperate Zones, or Belts of the Earth, because they never 
 suffer either from the excessive heat of the Sun's vertical 
 rays, or from excessive cold. These are the most pleasant 
 and healthy parts of the world to live in. And those 
 around the Poles, inside the Polar Circles, though not, 
 like the former, shaped like belts upon the Earth's surface, 
 are yet called the Frigid or Cold Zones. 
 
 About March 21 and September 21, as has been shown. 
 
76 FIRST LESSONS IN SCIENCE. 
 
 the Sun is vertical for places on the Equator. And now, 
 as the Earth turns round, each place on its surface will 
 be for twelve hours in the light, and for twelve in dark- 
 ness. Hence days and nights will he equal all the world 
 over at these seasons, which are called the Equinoxes 
 (^Equinox equal night), and happen in Spring and Autumn. 
 The Spring or Vernal Equinox, at places north of the Equa- 
 tor, will be about March 21, and the Autumnal Equinox 
 about September 21 ; and the contrary will be the case at 
 places south of the Equator. At these times there will be 
 six hours of sunlight before Noon, and six after Noon, all 
 over the world : in other words, the Sun will rise all 
 over the world at six o'clock in the morning, and set at 
 six in the evening. About June 21 he begins to enter 
 Cancer, and about December 21 he begins to enter 
 Capricorn. The first of these days (June 21) is the 
 longest day for places in the North Temperate Zone, the 
 Sun being then more nearly vertical to such places than 
 at any other time of the year ; and it is, of course, the 
 shortest day for places in the South Temperate Zone. 
 And the opposite is true of December 21. 
 
 Thus we see the wondrous Wisdom with which our 
 Heavenly Father has contrived this globe, to be the dwell- 
 ing place of such a creature as man, and made all these 
 plans for our comfort, as well, as we may be sure, for a mul- 
 titude of other reasons which we are not able to imagine. 
 
 39. There are some words made use of in referring to 
 the Earth's surface, as well as to the places of the Sun, 
 Moon, and Stars, in the regions of the sky, which I must 
 here explain. 
 
 The Equator, as you already know, is, properly speak- 
 ing, a circle drawn around the Earth midway between 
 the two Poles. The parts of the Earth, North and South 
 of the Equator, are called the Northern and Southern 
 
FIRST LESSONS IN SCIENCE. 77 
 
 Hemispheres. The centre of the Equator is the same as 
 the Earth's centre, and so the plane of the Equator will 
 pass through the Earth's centre. Now, if we suppose the 
 Heavens to be (what they seem to be) a. hollow spherical 
 canopy, surounding the Earth on all sides, and then 
 imagine the plane of the Equator to be stretched out in 
 directions till it meets this canopy, it will mark upon it 
 a circle, corresponding to the Equator on the Earth's 
 surface. This circle is called the Equator of the Heavens, 
 or the Celestial Equator, while that drawn upon the Earth 
 is called the Terrestrial Equator. Hence we may speak 
 of the Sun or a Star being seen in the Equator, meaning 
 the Celestial Equator. 
 
 The Ecliptic again, is, properly speaking, the orbit in 
 which the Earth, or rather the Earth's centre, goes 
 round the Sun's centre. So the plane of the Ecliptic 
 passes through the Earth's centre ; and, if this plane be 
 supposed to be stretched out on all sides around the 
 Earth's centre till it meets the Heavens, it will mark out 
 a circle on the Celestial Vault of which the Earth's centre 
 will be the centre, and which will be the Celestial 
 Ecliptic. Hence we may speak of the Sun or a Star being 
 seen in the Ecliptic. The same plane will also cut the 
 surface of the Earth, in a circle of which the Earth's 
 centre is the centre, and which will be called the Terres- 
 trial Ecliptic. 
 
 40. The Terrestrial Meridian of any place on the Earth's 
 surface is a circle, passing through the North and South 
 Poles, and through the place. It is plain that the Earth's 
 centre is the centre of the Meridian, since it passes 
 through the two Poles. And as the Equator divides the 
 whole globe into two Hemispheres, the Northern and the 
 Southern, so the Meridian divides the whole globe into 
 two Hemispheres, the Eastern and Western, but only of 
 
78 FIEST LESSONS IN SCIENCE. 
 
 course with respect to that particular place, whose Meridian 
 it is. If the plane of the Meridian be supposed stretched 
 out in all directions to meet the Heavens, it will mark out 
 the Celestial Meridian of the place in question. And 
 this will go from North to South directly ahove the place 
 through the point overhead, or Zenith, as it is called, 
 dividing the whole of the sky, which is visible from the 
 place, into two equal parts, the Eastern and Western, 
 and marking the North and South points of the horizon, 
 where it cuts it. 
 
 The Horizon, as you have been told, is the circle 
 which bounds in our view at any place, or which would 
 bound it in, if there were no hills or mountains to prevent 
 the line being fully and evenly formed. And if the 
 plane of this circle be supposed stretched out like the 
 others to meet the Heavens, it will mark out the Celestial 
 Horizon. Hence, when the Sun or a Star is rising or 
 setting, it seems to cross this Celestial Horizon; and 
 when, as the Earth turns round on its axis, or the whole 
 vault of Heaven seems to turn round, the Sun or Star 
 has got to its highest point midway between its rising 
 and setting, it will just at that moment be crossing the 
 Celestial Meridian of the place. In observatories, or 
 places where the Stars are carefuUy watched, there is 
 always what is called a transit instrument, fixed so as to 
 turn round in the plane of the meridian, in order to 
 observe the meridian transit (or passing over) of any 
 heavenly body. When the sun passes over the meridian 
 of a place, he has then reached his highest point in the 
 sky for that day at that place, that is, it is then the hour 
 of noon for that place. 
 
 41. The Latitude of a place is its distance from the 
 Equator, North or South, measured by degrees, &c., along 
 the meridian of that place. Thus the latitude of the 
 
FIRST LESSONS IN SCIENCE. 79 
 
 Observatory at Greenwich, near London, is 51° 28' 40' 
 Nortii, and the latitude of Pietermaritzburg in Natal is 
 about 29J° South. For convenience of seeing roughly at 
 a glance the latitude of a place, circles are drawn upon a 
 globe, parallel to the Equator, at equal intervals, called 
 parallels of latitude. These circles are not great circles 
 whose centres are the centre of the earth, as the Equator, 
 &c. ; but they will get smaller and smaller as they are 
 drawn nearer to the Poles. There is also a circle of brass 
 attached to a globe, so as to pass through the two Poles, 
 as the meridians do. By turning round the globe, any 
 place may be brought under this brazen meridian, which 
 acts then as the meridian of the place, and its latitude 
 may be read off at once upon it. 
 
 The Longitude of a place is the distance measured in 
 degrees, &o., along the Equator of that point in which 
 the meridian of the place cuts the Equator, from some 
 fixed point in the Equator. This fixed point with 
 English observers, is usually the point where the meridian 
 of Greenwich cuts the Equator. And they reckon East 
 or West of it as far as 180°. Thus the longitude of 
 Pietermaritzburg is about 30 J° East of Greenwich. 
 
 For convenience of seeing roughly at a glance the 
 longitude of a place, a number of meridian lines are drawn 
 upon the globe at equal intervals. Also by bringing the 
 place under the brazen meridian, so making the brazen 
 meridian to be the meridian of the place for the time 
 being, and observing where it crosses the Equator, we can 
 read off at once more exactly the longitude of the place. 
 
 When we know the latitude and longitude of a place, 
 we can put our finger at once upon the spot where the 
 place should be found upon a globe or map. But on a 
 map, which is a flat piece of paper, we cannot of course 
 show the circles as they are really upon a globe. They 
 
80 FIRST LESSONS IN SCIENCE. 
 
 are represented by lines, drawn straigM or curved accord- 
 ing to certain rules, so as to distort as little as possible 
 the outlines of countries from wbat they really are upon 
 the globe, or so as to answer some other special purpose, 
 intended by the maker of the map. 
 
 42. We have seen that the Equator and Ecliptic, as 
 drawn upon the surface of a Terrestrial Globe, repre- 
 senting the Earth's convex surface, have corresponding 
 circles in the starry vault, where their planes, stretched 
 out on every side, seem to meet the concave (or hollow) 
 surface of the Heavens. All such lines, then, may be 
 drawn upon the surface of a Celestial Globe, representing 
 the appearance of the Heavens. Only, as we cannot of 
 course, get to stand at the centre of such a globe, we are 
 obliged to draw them on its convex outer surface, instead 
 of drawing them on the concave inner surface, as they 
 ought to be drawn, in order to represent exactly what is 
 seen from the Earth. 
 
 The Bight Ascension of a point in the sky corresponds 
 exactly to the longitude of a place on the Earth, being 
 measured along the Celestial Equator,. East or West, from 
 a fixed point in the Equator. But that fixed point is the 
 same with all Astronomers, namely, the point where the 
 Ecliptic cuts the Equator, when the Sun seems to pass to 
 the North of the Equator. At this point he is just going 
 to enter the sign Aries. 
 
 The Declination of a point in the sky corresponds to the 
 latitude of a place on the Earth, being measured Nortb and 
 South of the Equator on what may be called the meridian 
 of the point, that is to say, on a great circle passing 
 through the two Poles and the point itself. 
 
 When we know the Eight Ascension and Declination 
 of a heavenly body, we know exactly where it is to be 
 found in the sky. 
 
FIRST LESSONS IN SCIENCE. 81 
 
 43. Vertical Circles are great circles of the Heavens, 
 which, like the Celestial Meridian, pass through the 
 Zenith of a place, but do not pass through the Poles, and, 
 therefore, do not cut the horizon in a North and South 
 Line, as the meridian does. The planes of all such circles 
 are vertical planes. And all planes parallel to the 
 horizon are horizontal planes. 
 
 The Altitude of a point in the sky is its distance from 
 the horizon in degrees, &c., measured on a vertical circle 
 passing through the point. 
 
 The Azimuth of a point in the sky is the distance 
 measured in degrees along the horizon, of the point where a 
 vertical circle passing through the point cuts the horizon, 
 from the North or South point of the horizon. 
 
 When the altitude and azimuth of a heavenly body are 
 known, as it is seen from a certain place upon the Earth, 
 the place of the body in the sky is known, as seen from 
 that place. And then, if the latitude and longitude of 
 that place be known, it is easy by certain rules of calcula- 
 tion, to make out on paper what the Eight Ascension and 
 Declination of the body are — that is, to fix its place in the 
 sky. Now, at all observatories, instruments are at hand 
 carefully prepared for this purpose of observing altitudes 
 and azimuths, as the first step towards fixing the place of 
 bodies in the sky, the latitude and longitude of the place 
 itself being first very accurately ascertained. 
 
 44. Since the Earth turns round on its axis once in 
 24 hours, if we divide the whole Equator into 24 equal 
 parts of 15° each (so that the whole circle will contain, as 
 it ought, 360°), and through the points of division draw 
 24 meridian circles, passing, as all meridians must, 
 through the Poles, then, as the Earth turns round, one of 
 these meridians will pass under the Sun every hour. 
 Suppose, for instance, that one of these meridians passes 
 
 o 
 
82 FIRST LESSONS IN SCIENCE. 
 
 through Greenwich, and that is now uncler the sun, or, in 
 Other words, that the sun is on the meridian of Green- 
 wich, BO that it is noon at Greenwich, and at all places of 
 course on the same meridian. Then an hour afterwards, 
 as the Earth turns from West to East, the Sun will be on 
 the meridian which lies 15° to the West of Greenwich ; 
 that is, it wUl be noon at all places on that meridian, 
 which have, therefore, 15° West longitude, an hour later 
 than it is noon at Greenwich. Eor places 30° West of 
 Greenwich it will be two hours later, and so on. On the 
 other hand, the Sun has been upon the meridian 15° East 
 of Greenwich an hour before it was on the meridian of 
 Greenwich ; so that when it is noon at Greenwich, it is 
 an hour past noon at all places which have 15° East 
 longitude, two hours after noon for places 30° East of 
 Greenwich, and so on. Since 15° of longitude. East or 
 West, makes a difference of one hour, or sixty minutes, in 
 the time of two places, it follows that 1° of longitude will 
 make a difference of four minutes : that is, at any place it 
 will be four minutes later or earlier in the day than it is at 
 Greenwich, for every degree of longitude which the place 
 has East or West of Greenwich. Hence, since Pietermaritz- 
 burg is about 30J° East of Greenwich, it will be about two 
 hours later in the day than it is at Greenwich. When it is 
 noon at Greenwich, it will be two o'clock in the afternoon 
 at Pietermaritzburg, which is expressed by 2 p.m. (where 
 P.M. stands for the Latin words Post Meridiem, afternoon). 
 So when at Greenwich it is six in the morning, or six a.m. 
 (where a.m. stands for Ante Meridiem, before noon), it 
 will be 8 A.M. at Pietermaritzburg. 
 
 45. I will now explain to you the nature of those winds 
 called the irade-j««wd«, which we feel, as I told you in (13), 
 because of the Earth turning round on its axis. The 
 first mention of these was made by the great navigator 
 
FIRST LESSONS IN SCIENCE. 83 
 
 Columbus, wlio set out from Spain in the year 1492, 
 determined to sail continually to the West till he came to 
 land. He expected to reach the Eastern shores of Asia, 
 but he came upon one of the West Indian islands, and 
 was the first to discover America, which was then un- 
 known to those who lived in the Old World (as it was 
 called), that is in Europe, Asia, and Africa. The account 
 of this voyage is a most deeply interesting story, which I 
 shall hope to tell you at length in another book. I wish 
 now to mention only that part of it which concerns the 
 discovery of the trade winds. Columbus was engaged in 
 a business of great danger. He had to cross an unknown 
 sea, with a company of ignorant and fearful sailors. 
 Most of them had been forced to go against their will by 
 the orders of the King of Spain, and they thought that 
 they were being carried away from all their friends and 
 kindred into some far off region, from which perhaps, 
 they should never come back. When, however, they 
 found themselves wafted rapidly over a tranquil sea by a 
 pleasant breeze blowing steadily from East to West, their 
 fears gradually subsided. But when this wind was found to 
 continue in the same direction for days and weeks together, 
 they began to think that the wind in these seas might 
 always blow from the East, and, if so, they should never be 
 able to get back to their native land again. They implored 
 Columbus to try to turn back before it should be too late. 
 When he refused, and the wind still blew on steadily 
 from the East, the sailors began to murmur loudly. He 
 managed to soothe them down and quiet them, two or 
 three times, but at last they broke out in open mutiny 
 and threatened to throw him overboard if he persisted in 
 sailing any further to the West. He begged them to 
 wait only three days longer, and if land was not found 
 within that time he promised to go back to Spain. On 
 
 G 2 
 
84 FIEST LESSONS IN SCIENCE. 
 
 the third day they discovered an island, to which he gave 
 the name of San Salvador. In this way the trade-winds 
 became first known at the same time as the New World. 
 Columbus returned to Europe by the help of the ordiuary 
 winds, going to the North of that belt of the Ocean, over 
 which the trade-winds blow. 
 
 46. The trade-winds, then, are winds which are always 
 found to blow from the East for a certain distance on 
 each side of a belt of ocean near the Equator, blowing 
 from the North to the North of the Equator, and from the 
 South to the South of the Equator. Suppose a ship 
 sailing from England to the Cape. Soon after passing 
 Madeira, it will get into the Northern trades, and find the 
 wind blowing from the North. As the ship goes south- 
 ward, passing the Canaries and the Cape de Verd Islands, 
 the wind will gradually veer round towards the East, but 
 still it will blow on the Northern side of East. At 
 last, before it reaches the Equator, the trade-winds will 
 cease to be felt, the distance from the Equator at which 
 this takes place, being greater or less according to the 
 season of the year. "When the Sun is vertical North of 
 the Equator or Equinoctial Line, that is, from March 21 
 to September 21, the Northern trade-winds will not come 
 so near to the Line as in the other half of the year, when 
 the Sun is South of the Line from September 21 to 
 March 21. When the ship has got fairly into the trades, 
 the sailing is delightful. The vessel moves on steadily 
 day after day, and the sailors have seldom to touch a sail 
 or rope. The sea is smooth, and the sky serene. By day 
 the warm sunny air is cooled by the pure fresh breeze ; 
 the night is almost as warm as the day, and the clear blue 
 sky is lit up by the _silvery moon and brilliant stars. 
 On all sides of the ship may be seen flying-fish, and 
 dolphins and porpoises, playing about in the waters. An 
 
FIEST LESSONS IN SCIENCE. 85 
 
 open boat might cross the ocean safely in these regions. 
 On this account the Spaniards, when they first sailed 
 over this part of the sea, called it " the Ladies' Sea." 
 
 47. As the ship goes on out of the Northern trade-winds 
 towards the Equator, she enters a region of calms and 
 variable winds, where, perhaps, she may roll about for 
 days, or even weeks, creeping along by the help of every 
 puff of air that can be caught, but often drenched with 
 torrents of rain, and surprised with heavy squalls of wind 
 and thunderstorms. The sky is now covered with white 
 clouds and the air very sultry and oppressive, loaded with 
 moisture, which makes every thing feel clammy to the 
 touch. However, at la';t, perhaps in one week, or perhaps 
 in three or six, she will get through this tedious part of 
 her voyage. I am speaking of a sailing vessel : a steam- 
 ship will put on all her power, and press through this part 
 of her course as soon as possible. Then, while still North 
 of the Equator, she will begin to feel the Southern trade, 
 blowing, at first, almost from the East, then veering round 
 more and more towards the South. This wind will 
 compel the ship to go very near the coast of South 
 America, advancing southward, however, all along, till it 
 will get out of the Southern trades, and find westerly 
 winds, which prevail in these parts, and so, by the help 
 of these will reach the Cape. 
 
 48. Coming back from the Cape, the ship will be 
 troubled, at first, with the westerly winds ; but sailing in 
 a zigzag course, as best she can, she will get, at last, into 
 the South-East trades, and go merrily on to St. Helena, 
 where almost all homeward-bound ships stop to take in 
 supplies of food and water. Still the trade lasts on, be- 
 coming now more easterly, till the ship crosses the Equator, 
 gets again into the doldrums, as sailors call that disagree- 
 able part of the voyage, and experience again light variable 
 
86 FIRST LESSONS IN SCIENCE. 
 
 winds, blowing from all quarters, long calms, and, now 
 and then, a furious squall, and heavy rains. In July and 
 August, however, there are often light southerly winds, 
 which help a ship along in these parts. And, at all 
 seasons of the year, the homeward voyage to England is 
 more easily made than the outward. The ship will, at 
 last, get, into the North-East trades, and be obliged to 
 go at first towards the coast of North America, tUl 
 she can steer North, or even North-East, make for the 
 Azores. Getting out of the trades, it will generally 
 find westerly winds, as it did about the Cape, which 
 will carry it to England, and up the British Channel. 
 These westerly winds prevail in these parts so much, 
 that the voyage from America to England, that is, from 
 West to East, may be performed in 23 days, while that 
 from East to West, from England to America, takes about 
 40 days. 
 
 49. The cause of the trade-winds is thus explained. The 
 Sun's powerful rays, in the tropical regions of the Earth, 
 over which he is vertical from time to time, causes the air 
 in these parts to become heated, and so to expand, and be- 
 come lighter, and ascend to the higher regions of the sky. 
 Meanwhile, cooler air rushes in from each side, from the 
 North and from the South, to fill up the vacancy. This 
 accounts for the trade-wind blowing, at first, from the 
 North or South, when a ship begins to feel it. But the 
 air will have been moving round from West to East, 
 together with the Earth, as it turned upon its axis, and at 
 the same rate as the places from which it came. Now these 
 places, being nearer the Poles than the Equator, will not 
 be carried round through so large a circle, in the 24 hours, 
 as places nearer the Equator — that is, they will not have 
 so quick a motion from West to East as places near the 
 Equator have. Hence the air from the North or South, 
 
FIRST LESSONS IN SCIENCE. 87 
 
 ■when it reaches the Equatorial regions, will not be moving 
 so fast towards the East as the ocean, or land, to which it 
 has come. So, as the Earth turns round, the ocean or land 
 will be carried towards the East with a more rapid motion 
 than the air above it, and will rub, as it were, against the 
 air : that is, the air will be felt as a wind coming from the 
 Easterly direction, and more and more so, as the ship gets 
 nearer to the Equator, and so the difference between the 
 Eastward motion of the air from the North or South, and 
 that of the land or sea becomes greater. Hence we see 
 how the wind on the North side of the Equator is felt first 
 as a North wind, then is felt more and more from the East, 
 and, at last, when it goes on further to the South, is felt 
 only as an East wind. And the like takes place with the 
 Southern trade-wind on the other side of the Line. Only 
 there is so much more land in the Northern Hemisphere 
 than in the Southern, that the Northern is the hotter of the 
 two ; and the belt of greatest heat does not lie equally on 
 each side of the Equator, but almost wholly on the 
 Northern side of it. Hence the Southern trade-wind goes 
 nearly to the Equator, and sometimes even past it ; while 
 the Northern trade never goes down so far as to the 
 Equator. 
 
 50. Meanwhile the hot air, which has ascended into the 
 higher regions from the parts near the Equator, will get 
 cooled, as it mounts, throwing off its heat into the vast 
 regions of space, and wiU travel high overhead, above the 
 currents of air that are flowing from the North and South, 
 to fill up the places thus left empty. At last, these upper 
 currents will come down to the surface of the Earth at 
 some distance on each side of the Equator. But the air, 
 which thus descends, will still be moving from West to 
 East, at the rate at which it was moving, when it first as- 
 cended near the Equator; it will be moving, therefore. 
 
00 FIRST LESSONS IN SCIENCE. 
 
 much, more rapidly than the land or ocean on which it falls, 
 at parts of the Earth's surface more distant from the 
 Equator. It will rush towards the Bast, more speedily 
 than these places will move, hy the turning of the Earth 
 about its axis. And they will feel, in consequence, a wind 
 coming from the West. This accounts for the westerly 
 breezes which prevail both North of the Northern, and 
 South of the Southern, trade-wind, as it occurs in the 
 great Atlantic and Pacific Oceans. Other similar effects 
 are produced in other parts, as in the Indian Ocean and 
 Gulf of Mexico, though modified, of course, by the different 
 shape of the land. 
 
 51. Nothing has yet been said about the Moon, which, 
 however, is an object of great interest to us, only less than 
 that with which we regard the Sun. It seems, indeed, to our 
 eyes, to be. nearly as large as the Sun, when we see them 
 both in the sky at the same time. But this is only because 
 it is so near to us ; for it is really a very small body. In - 
 fact, it would take about 60 Moons to make up the bulk of 
 the Earth ; whereas, you have been told, it will take more 
 than a million Earths to make up the bulk of the Sun. 
 As the Earth goes round the Sun once in 365 days, or a 
 year, so the Moon goes round the Earth once in 28 days* 
 And this is going on all the while that the Earth itself is 
 going round the Sun. So that the Earth takes the Moon 
 along with it, as a kind of attendant. And on this account 
 the Moon is called the Earth's satellite, from the Latin 
 word satelles, for hodyrguard. Hence it. is that the Moon 
 has not only an apparent motion from East to West, 
 as the Stars have by reason of the Earth turning round 
 upon its axis. But it has a real motion also of its own, by 
 reason of its going round the Earth, in a direction from 
 West to East, the opposite to its apparent motion. If it 
 had no motion of this kind, it would rise to-morrow, by 
 
FIRST LESSONS IN SCIENCE, 89 
 
 reason of the Earth turning round, just 24 hours after it 
 rose to-day. But this motion of its own, in the opposite 
 direction to its apparent motion, makes its apparent daily 
 motion seem less than that of the Stars. They seem to go 
 at such a rate that they get round the Earth in 24 hours. 
 But the Moon seems to go more slowly, because she travels 
 •^ith her own real motion in the opposite direction. And 
 so she lags behind the Stars and will rise to-morrow 
 about 60 minutes, or nearly an hour, later than she does 
 to-day. 
 
 62. We know that the Moon shows to us different 
 appearances, or phases, as they are called. Let us see 
 what is the cause of this. The fact is, that she gets all 
 her light from the Sun, as the Earth and the Planets do. 
 But, of course, only one side of her body, that turned to- 
 ward the Sun, can be bright with his light at one time ; 
 the other side, that turned away from the Sun, will be dark 
 and not visible.^ Now as the Moon goes round the Earth, 
 she comes into different positions, so that we see more or 
 less of her bright side at different times. Thus, for 
 instance, at one time, she is on the same side of the Earth 
 as the Sun ; and then her dark side is turned towards us, 
 and we cannot see her at all for a day or two, unless, in- 
 deed, it should so happen, as it does at certain times, that 
 she comes just between the Earth and the Sun, and then 
 she will hide from us for a while more or less of tbe Sun's 
 face, and the Sun is said to suffer an eclipse, from a Greek 
 word which means " failing out," because the Sun seems to 
 " fail out " of his place. " But how is it," you may ask 
 " that she does not always get between the Earth and the 
 Sun, every time she goes round the Earth, that is, once 
 every month? " It would be so, if she went round the 
 Earth in the plane of the Ecliptic, in which the Earth 
 goes round the Sun. Then, every time she got round the 
 
90 FIRST LESSONS IN SCIENCE. 
 
 Earth to the side on 'whicli the Sun is, she would get her 
 body between the Earth and Sun, and eclipse the Sun's 
 face. But the Moon goes round in a plane, which is a 
 little inclined to the plane of the Ecliptic at an angle of 
 about 5°. And as she goes round the Earth in her orbit, 
 she passes through the Ecliptic .twice every month. At 
 one time she ascends to run through the Northern half of 
 her orbit ; and then, after fourteen days, she descends again 
 to run through the Southern half. The places, where she 
 thus passes through the Ecliptic, are called her nodes; 
 and thus the Moon reaches an ascending or descending 
 node at intervals of fourteen days. At such times, then, 
 she is in the plane of the Ecliptic ; and, if she also happens 
 to be passing between the Earth and the Sun, as, of course, 
 she must do every time she goes round the Earth, the Sun 
 will be eclipsed. Or if she is very near the node, when she 
 has got round to that side of the Earth on which the Sun 
 is, she may hide from our sight a part of the Sun's face 
 and he will be partially eclipsed. 
 
 53. Sometimes, then, in an eclipse of the Sun, only a little 
 piece of its bright face is darkened — sometimes a larger 
 portion. Sometimes, there may be what is called an 
 annular, or ring-like, eclipse, when the Moon's disk hides 
 from us the greater part of the Sun's disk, but is not large 
 enough to cover the whole of it, and so leaves a bright 
 ring of the Sun's disk still shining behind the black disk 
 of the Moon. Sometimes, again, there may be what is 
 called a total eclipse, and we lose sight for a short time of 
 the Sun's face entirely. This arises from the fact, about 
 which I will tell you more farther on, that the Earth's orbit 
 about the Sun is not quite a circle ; so that sometimes the 
 Sun is farther off from the Earth than at others, and his 
 disk is, therefore, smaller, and so the Moon's disk can cover 
 it entirely. At such times of total eclipse, a strange 
 
FIRST LESSONS IN SCIENCE. 91 
 
 appalling darkness settles down upon the Earth. The 
 birds cease their songs and go to roost. The cattle begin to 
 go home, as if it were evening. The flowers shut up their 
 blossoms. The sky has a violet, purple-black, or yellowish- 
 crimson hue ; the sea appears of a lurid red ; human faces 
 look ghastly ; all nature seems stricken with dismay and 
 dread. At last, the Moon's disk passes away from before 
 the Sun's face, and the light of day returns, by degrees as 
 before. Now that we are able to explain how an eclipse of 
 the Sun takes place, there is nothing surprising or dreadful 
 in it. But ignorant people, and rude and untaught savage 
 nations, are always much frightened when an eclipse of 
 this kind occurs. They make sure that something awful 
 is about to happen — a fierce, bloody war, perhaps, or a 
 destroying pestilence, the death of their king, or, it may 
 be, the end of the world. Now, however, so certain is the 
 knowledge, which astronomers have of these things, that 
 they can tell exactly the time when an eclipse is to take 
 place, hundreds of years beforehand — can fix the very 
 moment, when it will begin and end, and say how much of 
 the Sun's face will be darkened. 
 
 If, however, the Moon, when passing between the Earth, 
 should not be near enough to a node, there can be no 
 eclipse. And astronomers have shown that there may be 
 five eclipses of the Sun in each year, and that there must 
 be two. 
 
 54. But now suppose that about a week has passed since 
 the time of new moon. In that time the Moon will have 
 got about a quarter of the way round in its orbit about 
 the Earth. Hence, as it moves from West to East, we 
 may expect, when the Sun is just setting in the West, 
 to find the Moon high up above our heads, having 
 moved so far towards the East from the Sun in that 
 time. Now, however, its bright side being that which 
 
92 FIRST LESSONS IN SCIENCE. 
 
 looks towards the Sun, we can see only about a half of it, 
 while the other half of its face, which the Moon presents 
 to us, will be half of its dark side. When a week more 
 has passed, the Moon will have got still further towards 
 the East, going on in its path about the Earth. And, 
 when the Sun is just setting, as before, we shall now see 
 the Moon in the East just rising, and shall be able to see 
 the whole of her bright face, except when she happens to 
 be in or near a node, and then the Earth's body will lie be- 
 tween the Sun and the Moon, and the Moon will fall into the 
 Earth's shadow, and be eclipsed. It may be shown that 
 there may be as many as four eclipses of the Moon in a 
 year, or there may be none at aU. On such occasions, it 
 is seen that the shadow of the Earth, which is seen to 
 pass over the Moon's face, as she enters into the darkness, 
 is always circular ; from which we learn that the form of 
 the Earth is certainly that of a globe. We now see the 
 reason why the Earth's orbit has been called the Ecliptic, 
 because it is only when the Moon is in or near a node, 
 and, therefore, in or near the plane of the Earth's orbit, 
 that an eclipse, either of the Sun or Moon, can take 
 place. 
 
 55. When another week has passed, the Moon will have 
 separated from the Sun still more ; and now, when the 
 Sun is setting in the West, the Moon will have got to be 
 right under our feet. Of course, we cannot see it then at 
 all. But, some hours after sunset, the Earth will have 
 turned round so far as to bring the Moon into view, so 
 that she wiU rise about midnight. But she will show us 
 only half of her bright face, which will be turned, of 
 course, full towards the Sun, as we shall see plainly at 
 sunrise, when the Moon will be up above our heads. A 
 week after this she will rise and set with the Sun once 
 more, as at first, and her dark side will be turned again 
 
FIEST LESSONS IN SCIENCE. 93 
 
 towards us, and she will be no longer visible. At such 
 time, the Zulus, and, I suppose, many other untaught 
 people like them, say that the old Moon is dead, and 
 another new Moon will come in to being. 
 
 Thus are explained the four chief phases of the Moon, 
 between which, of course, she takes others, sometimes 
 smaller, sometimes larger, than the half of her bright 
 face. In the first quarter of her course, for a week after 
 new-moon, she takes the form of a hollow curve, which is 
 called a crescent, the hollow being turned away from the 
 Sun, but the bright part getting larger and larger daily 
 till we see the half-moon. In the second quarter she has a 
 bulging, or, as it is called, a gihhous form, the bulge being 
 toward the Sun, that is, towards the West, and the bright 
 part getting larger daily till we see the whole full-moon. 
 In the third quarter, her form also appears gibbous, but 
 the bulge is now on the other side, towards the East, 
 on which side the Sun now is, and the bright part gets 
 smaller daily, till she shows again her half-face. And 
 then, in the fourth quarter, we see the crescent again, 
 with the hollow towards the West, dwindling down by 
 degrees to a fine silver thread, till we loose sight of her 
 altogether. 
 
 66. But, though it is true that the Moon gets round the 
 Earth in about 28 days, yet it does not follow that, if it 
 be full-moon to-day, it will be full-moon again after 28 
 days exactly, because during that time the Earth will have 
 gone on in its orbit about the Sun, and so will have 
 shifted its place with regard to the Sun. And, on this 
 account, the Moon will have to go on some distance 
 further in its course, beginning to go round the Earth a 
 second time, before it will get into such a position with 
 regard to the Sun as to show the full moon. This will 
 appear more plainly by help of a figure. So draw a large 
 
94 FIRST LESSONS IN SCIENCE. 
 
 circle to represent the Earth's orbit, and put S in the 
 centre to represent the Sun. Let E be the Earth in some 
 part of its orbit; and (supposing now that the Moon 
 moves in the plane of the Ecliptic, as it nearly does) in 
 the line SH produced, take a point M to represent the 
 Moon, in opposition, that is, in the position of full-moon, 
 on the opposite side of the Earth to that on which the Sun 
 is. At the end of 28 days, let e be the place to which the 
 Earth will have got in its orbit. Draw em parallel to 
 SEM ; and let m represent the Moon, which has got 
 round the Earth, while it moved from E to e, and now is 
 seen from e in the same part of the sky as M, when it was 
 looked at from E. For the Fixed Stars are so far off, that, 
 if EM and em be supposed to be lengthened out, or pro- 
 duced, to reach the same place among the Stars, though, 
 of course, these lines would meet at last, yet their place 
 of meeting will be such a vast way off, that they will 
 seem to our eyes to run parallel to one another. They 
 must, in fact, be slightly inclined to one another. But 
 the inclination is so very slight, that neither our eyes, 
 nor the finest instruments which can be made, are able to 
 detect it. But now, plainly, e does not lie between S and 
 m, as E did between S and M ; so that m will not appear 
 to e as the full-moon. The Moon must still move on a 
 little farther in its path about the Earth, while the Earth 
 too moves on in its path round the Sun, till the Earth's 
 place, which we may mark by e', lies between the Sun, S, 
 and the Moon's place, m' ; and then will be seen from the 
 Earth the full-moon. Thus we see that the Moon does 
 not go through all its phases in the same time that it goes 
 round the Earth. It takes 28 days (more strictly, 27j 
 days) to do the latter. But it takes 29i days to pass from 
 one full moon, or one new-moon, to another. Since 13 
 times 27j is 364|, the Moon will go thirteen times round 
 
lb face page 94. 
 
FIRST LESSONS IN SCIENCE. 95 
 
 the Earth in a year, with some days to spare. But since 
 12 times 29J is 354, there wUl only he twelve full-moons 
 in that time. 
 
 57. And here let me explain that the Moon's path in 
 space is not exactly what you might suppose. It is a 
 circle as far as the Earth is concerned, that is to say, to 
 us living upon the Earth the Moon seems to go round in a 
 circle, and we may make all our reasonings about it, as 
 if it did. But we must not forget that the Earth itself is 
 moving on all the while. And, therefore, it is impossible 
 that the Moon's path in space should be a circle. I may 
 be able to give you some idea of the actual path of the 
 Moon in space by means of a figure. 
 
 Draw a large circle, as before, to represent the Earth's 
 orbit, with S for the Sun in its centre. Draw on another 
 part of the paper a small circle with centre e, to represent 
 the Moon's orbit about the Earth. Divide this small 
 circle into four equal parts by two diameters, drawn at 
 right angles to one another ; and divide these parts equally 
 by two other diameters ; and put letters, m, n, o,p, q, r, g, t, 
 at the points, where these four diameters cut the cir- 
 cumference. So now we shall have the eight radii, em, en, 
 eo, &c. ; and these may represent so many distances of the 
 Moon from the Earth in eight different points of its orbit, 
 which we will suppose, as before, to be in the plane of the 
 Ecliptic. At first, then, suppose the Moon to be seen 
 from e in the direction em. In the other circle, draw S E 
 parallel to em, and produce it to M, so that EM may 
 represent the Moon's distance from the Earth. Then M 
 will be seen in the same direction from £ as m from e, and 
 may represent the moon, when full, as seen from E. 
 
 58. Now while the Moon goes on in its path about e, 
 and gets from m to n, suppose that the Earth goes on from 
 E to A. From A draw AN parallel to en, and equal in 
 
96 FIKST LESSONS IN SCIENCE. 
 
 length to EM. Then N will he seen in the same direction 
 from the Earth at 4 as w from e, and may represent the 
 Moon as seen from the Earth at A. 
 
 In like manner determine other points, 0, P, Q, &o., 
 representing places of the Moon, as seen from the Earth 
 in different parts of its path. And now join the points 
 M, N, 0, &c., by a sort of sweeping curve line. This will 
 give yon some idea of the kind of path, which the Moon 
 really describes in space, while still to the people on the 
 Earth, unconscious of their own motion, she seems to be 
 only going round the Earth in such a circle as mnopqrst. 
 In describing the curved line MNOPQBST, the Moon 
 really has gone round the Earth, as you see. But it has 
 done more. It has been going round the Sun at the same 
 time. And, in doing these two things, it has described 
 this strange curved line. In point, of fact the actual path 
 of the Moon is a wavy line, like this, which cuts the 
 Earth's orbit, going in and out thirteen times, but so as 
 always to have its concave, or hollow, side turned towards 
 the Sun. And, since the Moon's distance from the Earth 
 is only one four-hundredth part of the Earth's distance 
 from the Sun, it follows that the farthest distance, to 
 which the Moon can go outside or inside the line of the 
 Earth's orbit, must be very small indeed, compared with 
 the size of that orbit. In fact, if we take the circle, which 
 we drew in (15) to represent the Earth's orbit, the whole 
 wavy movements of the Moon, outside and inside that 
 orbit, must be included within the black line, which we 
 drew for the circumference of that circle. 
 
 59. Hence, just as we saw that we might call the Earth 
 a sphere, in spite of the little roughness on its surface, so 
 now we may say the Moon goes round the Sun very 
 nearly in a circle, in the same circle as the Earth, though 
 it does go a little outside or inside it, above the plane of 
 
'lofaeepage ^%, 
 
FIRST LESSONS IN SCIENCE. 97 
 
 the Ecliptic and below it, and by so doing manages to go 
 thirteen times also round the Earth while it is going once 
 round the Sun. 
 
 And this, indeed, is what we ought to expect ; for the 
 Sun attracts the Moon as strongly as he attracts the 
 Earth. And, in fact, though the Sun is so much farther 
 off from the Moon than the Earth is, yet his mass is so 
 enormous, that he attracts the Moon with a much greater 
 power than the Earth does, though the Earth is so near to 
 it. The force, with which the Earth attracts the Moon, is 
 only about two-fifths of that with which the Sun attracts. 
 And, therefore, if we pleased, we might speak of the 
 Moon, as going round the Sun in the centre, in a curve 
 which is nearly a circle, and which would be a circle, but 
 that the Earth disturbs its motion, and makes it go a little 
 in and out of the circle in the way above described. 
 However, as the Moon is plainly a satellite, or attendant 
 on the Earth, it is more usual to speak of it only as going 
 round the Earth, while the Earth itself goes round the 
 Sun — going round the Earth in a curve, which is nearly a 
 circle, and which would be a circle, but that the Sun 
 disturbs its motion, making it go a little in and out of its 
 proper path, sometimes accelerating or quickening, some- 
 times retarding or holding back, its motion. Observe, 
 however, it is not the whole pull of the Sun, which dis- 
 turbs the Moon's motion about the Earth, but only the 
 difference between his pull on the Earth and his pull on 
 the Moon at any moment, taking into account also the 
 directions in which these two pulls take place. This 
 disturbing force, therefore, is very small. 
 
 Several of the Planets also have Moons like ours, and not 
 one Moon only, but many. Thus Jupiter has four, which 
 go round about him at different distances, while he goes 
 round about the Sun, just as our Moon goes about the 
 
 H 
 
98 FIEST LESSONS IN SCIENCE. 
 
 Earth. So Saturn has eight Moons, and Uranns six. 
 Neptune, too, -has certainly two, and, possibly, others, 
 which have not yet been seen, being very small and 
 distant bodies. And these Moons might, of course, lite 
 our Moon, be considered as describing circles about the 
 Sun, and disturbed by the Planets about which they 
 revolve, which are called their primaries.* 
 
 60. The satellites of Jupiter are very famous in the 
 history of the science of Astronomy. They were first 
 seen in the year 1610, by Galileo, a famous Italian 
 philosopher, about whom I must tell you something. 
 Galileo, one day, while living at Venice, had heard that a 
 certain Dutchman had made a curious sort of a toy, in the 
 form of a long tube with a glass at each end, which, when 
 pointed towards any distant object, as a tree or a tower, 
 enabled a person looking through it to see the objects 
 seemingly brought nearer and made plainer, but turned 
 upside down. This was all that Galileo heard ; but lit 
 was enough to set him thinking. He began to consider 
 how this could be contrived ; and God had given him 
 great wisdom, and blessed him in the use he made of it. 
 He soon found that by putting certain curved glasses at 
 the end of a tube he could himself repeat the Dutchman's 
 wonder. The first eye- tube which he made, or telescope as 
 it is called, that is, " far-seer," made objects appear three 
 times as large as they otherwise would. But before long 
 he made another, which magnified eight times. And this 
 he turned to the skies, and saw, for the first time, with 
 delight and awe, what no mortal eye before had seen. 
 He saw that the Moon's face was, like that of the Earth, 
 ridged with high mountains, and furrowed with deep 
 
 * " The word Moon, taken to denote Bimply a satellite, is riot used 
 btiictly in its etymological meaning. The moon is simply the measurer, 
 as determining for us the length of the week ; hence the word month, 
 as indionting the moon's period of revolution." 
 
FIRST LESSONS IN SCIENCE. 99 
 
 valleys — that Mercury, Venus, and Mars showed phases 
 like the Moon — that Jupiter had four Moons, and that 
 Saturn had something strange about his form, which he 
 could not clearly make out, though now, by the help of 
 more powerful telescopes, we know very well what that 
 is — that the Milky Way is one vast mass of Stars, and that 
 the little bright misty spots, called nehulse (clouds), which 
 are seen here and there in the sky, are also clouds of star- 
 dust, each particle of which is in fact, as we know, a 
 glorious Sun ; or, perhaps, a world in a state of formation 
 — in short, that the whole Heaven is sown over, as it 
 were, with an immense multitude of Stars, too distant to be 
 seen by the naked eye at all. He saw all this and bowed 
 his head in reverence, and with his heart he glorified 
 God. 
 
 61. "When Galileo first caught a glimpse of Jupiter's 
 satellites, he saw only three of them close to the body of 
 the planet. He thought, at first, that they were only 
 very faint Fixed Stars. But, on the next night, he found 
 that they had changed their places ; and, watching them 
 again and again, he became certain that they were satel- 
 lites. So he boldly announced to the world that there 
 were in the heavens three Stars, which went round 
 Jupiter just as Jupiter himself went round the Sun. 
 After a little while he saw the fourth satellite. 
 
 And now how was this announcement received ? Many 
 there were who knew nothing about such matters, and 
 did not pretend to know ; and these were full of admira- 
 tion and delight, when they heard of his discovery, and 
 looked themselves through his tube. Galileo's telescopes 
 were in great request. They were made and sold every- 
 where ; and he himself had his time taken up for a whole 
 month in showing the new Stars to the chief people of 
 Venice. The true philosophers, again, who knew a little, 
 
 H 2 
 
100 FIEST LESSONS IN SCIENCE. 
 
 and knew also how little they knew, hut were longing to 
 know more, these, too, rejoiced in the joy of Galileo, and 
 felt that a great step had been made towards a better 
 knowledge of the heavens than as yet they possessed. 
 Among these was the noble Kepler, of whom you shall 
 hear more presently. But others there were who knew 
 nothing, but fancied they knew much — men, ignorant, 
 and yet obstinate in their self-conceit — who refused to 
 believe at all in the report of Galileo. Some said that his 
 eyes had been deceived, and that he had not really seen 
 the Stars he spoke of. Others scoffed at the notion of his 
 seeing them as if such a thing were even possible. One 
 person, who thought himself very wise, argued in this 
 way. " There are only seven openings in the head," he 
 said ; " there are only seven metals (as people' then 
 thought) ; there are only seven days in the week ; and so 
 there cannot be more than seven Planets " — by which he 
 meant the seven Planets of Ptolemy's system, namely, 
 the Sun and Moon, and the five Planets, known to the 
 ancients, and visible to the naked eye. Another refused 
 to look into the tube, lest he should be obliged to see the 
 new Moons, and confess that they were there. 
 
 62. At that time, indeed, Galileo himself, who was a 
 teacher of philosophy, appointed by the Government, had 
 been teaching all along according to the system of 
 Ptolemy, which was then believed by most people to be 
 true. He had long had great doubts upon the subject, 
 and had begun to see that the system of Copernicus was 
 very possibly the true one. But, perhaps, he did not as 
 yet feel' so sure about it, as to be ready boldly to assert 
 that the Earth went round the Sun. As time passed on, 
 howover, he became convinced of the truth of the views 
 of Copernicus, and wrote books, from time to time, in 
 which he expressed his opinions freely on this and other 
 
FIRST LESSONS IN SCIENCE. 101 
 
 matters, and ran no small risk in doing so. For in those 
 days it was thought a matter of religion to believe that 
 the Earth stood still, and that the Sun went round it, 
 because the Bible said so. The Bible said, that " God had 
 made the round world so fast that it cannot be moved." 
 Therefore, it was said, it must be true that the Earth 
 stands still. "A man must not dare to contradict the 
 Bible." You will not forget, I hope, what you have been 
 told, that the Bible was not given to make us wise in 
 matters of this kind, in things which God means us to find 
 out by searching, with the powers of mind which He has 
 given us — ^but to make us wise in matters which concern 
 the heart of man, to make us love and practise truth 
 and righteousness, to help us to be brave for speaking 
 and doing, at all cost, what we know to be good and just 
 and right, to be meek and patient under wrongs, to be 
 kind and loving, to be " pure in heart, that we may see 
 God." 
 
 63. At last, in 1613, one of Galileo's writings was 
 attacked in a book, as containing words contrary to the 
 teaching of the Bible, on the question of the Earth and 
 the Sun. He wrote a long letter in reply, in which he 
 showed that there was nothing contrary to religion in 
 believing that the Earth went round the Sun. And he 
 wrote with such power, that it only made those who 
 opposed him the more furious with rage, and determined 
 to crush him. Galileo, having heard of their intention, 
 asked leave of the prince, under whose protecting care he 
 lived, that he might go to Eome and face his enemies. As 
 soon as he reached that city, in 1616, he was seized by 
 officers of the Church of Eome, and charged with the 
 crime of holding the notion that the Earth moved and the 
 Sun stood stUl, contrary to the express words of Scripture 
 — with teaching this doctrine to others, with writing on 
 
102 FIEST LESSONS IN SCIENCE. 
 
 the subject to persons in foreign countries, and publishing 
 his opinions, and, worst of all, with trying to show that 
 these opinions were right, and did not overthrow the 
 truth of the Bible, in direct opposition to the judgment of 
 the Eoman Church. He was ordered to renounce them 
 at once, and to promise that he would neither hold, nor 
 teach, nor publish, any such wicked doctrines in future. 
 Galileo promised all this, and was then let go. Doubtless 
 he ought never to have made such a promise : for we dare 
 not deny the truth, which God in His Goodness is pleased 
 to reveal to us, and a man must not tell a lie to save his 
 life. But, before we judge him harshly, we must 
 remember that in those days men and women were burnt 
 alive for holding opiaions which the Church of Eome 
 condemned. However, so it was. Copernicus's book, and 
 some of Galileo's letters, were declared to be unfit to be 
 read. And for a time Galileo was silenced, escaping in 
 this way a gloomy dungeon, and a long and painful 
 imprisonment, perhaps, for the rest of his life ; perhaps, 
 also, cruel tortures and a dreadful death. 
 
 64. During the next two years Galileo was very quiet, 
 writing papers on matters of science, and receiving from 
 all quarters honours due to the labours of his life ; for he 
 had made other great discoveries, besides these in matters 
 of astronomy. But, at last, sixteen years afterwards, when 
 there was another Pope (as the chief Bishop of the Church 
 of Eome is called), he wrote again another book, setting 
 forth his old doctrine over again, and filled with pleasant 
 wit and stinging satire, against those who condemned 
 it. This roused up the fury of his old enemies into fresh 
 violence. Though an old man now, seventy years of age, 
 worn out and infirm, he was dragged again to Eome. His 
 prince, who was also his friend, tried to shield him in 
 vain. He was ordered to be tried on the same charges as 
 
FIEST LESSONS IN SCIENCE, 103 
 
 before. At first lie was shut up so closely that his health 
 began to fail. But his friends earnestly pleaded for him, 
 on the score of his old age and dignity, and he was allowed 
 more liberty till his trial should be brought to a close. It 
 took more than three months. First his books were searched 
 through and through for words which might be used to 
 condemn him. Then he himself was closely questioned. 
 And, last of all, he was called to make his defence. 
 The old man, however, had little to say for himself. It 
 was plain that he had broken the promise which he had 
 given so many years before ; and he could not, of course, 
 and would not, deny it. So on January 21, 1633, the 
 sentence was passed upon him, by these ignorant men, 
 that he should curse the " false doctrines,'' which he had 
 spent his life in proving to be true, and renounce them 
 utterly ; and that then he should be kept in prison as long 
 as the Pope thought good, and once every week, for three 
 years, should recite three psalms, expressing his contrition 
 for the grievous sin he had committed in teaching that 
 the Earth went round the Sun, when the Bible and the 
 Church of Eome said that it stood still. Galileo was 
 made to kneel down while the sentence was read to him. 
 But it is said that as he rose up from his knees he stamped 
 on the ground and whispered to a friend, " And yet it 
 does move." 
 
 65. He lived nine years longer, years of pain and 
 humiliation. He was ordered not to show himself in 
 public, and to confine himself to his own house in the 
 country, where he was strictly forbidden to receive any of 
 his friends. In addition to an old disease, from which he 
 suffered in his youth, he was now subject to another 
 bodily complaint, which caused him much pain. In 1634 
 he lost a favourite daughter, and two or three years after- 
 wards he lost the sight, first of one eye then of the other. 
 
104 FIRST LESSONS IN SCIENCE. 
 
 And yet the noble old man consoled himself amidst his 
 trials by making discoveries in science still, by God's help, 
 though he was not allowed to publish them to the world. 
 And, above all, he found comfort in putting his trust in 
 God, and patiently submitting to His Will. " Alas ! " he 
 once wrote to a friend, " your dear friend and servant Gali- 
 leo has become quite blind, so that this heaven, this earth, 
 this universe, which my own labours have wondrously 
 enlarged, a hundred thousand times beyond the belief of 
 bye-gone ages, is now shrunk for me into the narrow 
 space, which I myself fill in it. So it pleases God ; and 
 so it shall, therefore, please me also." Towards the end of 
 his life the strictness of his confinement was relaxed, and 
 he was allowed to receive the friends, who crowded to 
 him, as well as strangers from foreign parts, who had 
 heard his name, and wished to do him honour. Among 
 these was the poet Milton, who refers to him in the 
 ' Paradise Lost,' when he says — 
 
 " The Moon, -whose orb 
 Through optio glass the Tuscan artist views 
 At evening from the top of Ftsole, 
 Or in Valdamo to descry new lands, 
 Kivers, or mountains, in her spotty globe." 
 
 He died January 8, 1642, aged 78 years. 
 
 When Galileo was on his trial, he was asked if he 
 believed in God. Taking up a straw from the floor, he 
 replied, "The sight of this compels me to believe in 
 Him." In one of his books he wrote to this effect. " How 
 great and common a mistake it is for men to measure 
 God's Wisdom by their own, as if , that only were perfect, 
 which they see to be so ! If man had been told to plan 
 a scheme for the motion of the heavenly bodies, he would 
 have had things very different, more according to his 
 notion of what is proper and beautiful. He would have 
 
FIEST LESSONS IN SCIENCE. 105 
 
 arranged tlie Stars in perfect order, in squares and in 
 triangles, and other fine forms, the larger ones among 
 the middle-sized or less. And then he would think 
 that he had made the sky look very pretty. God has 
 just shaken them out from His Sand, as it were, as if by 
 chance. And we, poor simple creatures, must be thinking 
 that He has scattered them up yonder without order or 
 beauty ! " 
 
 66. It was by means of these same satellites of Jupiter 
 that it was first discovered that light, like sound, takes 
 time to travel. For the satellites of a Planet are, like the 
 Moon, often eclipsed, when they pass behind the body of 
 the Planet as seen from the Sun, that is, when they pass 
 into the shadow which Jupiter's body throws behind him, 
 away from the bright face of the Sun. Now, when these 
 eclipses were first observed, it was supposed that light 
 travelled in a moment, however great the distance might 
 be, and that any event, such as an eclipse, which took 
 place at the distance of Jupiter from us, would be seen by 
 us in the very instant in which it took place, just as if 
 we were present on the spot. But a Danish astronomer, 
 named Eoemer, in 1675, on putting together the times at 
 which these eclipses took place for several years, observed 
 that they always seemed to happen sooner when Jupiter 
 was nearest to us (that is, when the Sun and Jupiter were 
 on opposite sides of the Earth, or when Jupiter was in 
 opposition), and later, when he was farthest from us (that is, 
 when the Sun and Jupiter were on opposite sides of the 
 Earth, or when Jupiter was in conjunction'), than when 
 Jupiter was midway between these two positions. Upon 
 looking clo ely into the matter, he found out the cause of 
 this, namely, that light took time to come from Jupiter to 
 the Earth, though it travels very quickly, at the rate of 
 192,000 miles in a second, so as to reach the Earth from 
 
106 FIRST LESSONS IN SCIENCE. 
 
 the Sun, travelling a distance of 96 millions of miles, in 
 8 minutes 13 seconds, pr 8J minutes. If the sun were at 
 this moment blotted from the Heavens we should still see 
 him in his place, and all his motions would seem to go on 
 for 8^ minutes longer. 
 
 67. But you may be asking, " What is a telescope ? 
 and how has it power to make things appear nearer and 
 clearer to our eyes ? " I must try to explain this a little. 
 As to what light itself is, we must leave that question for 
 the present. It is enough for us to know that lights 
 whatever it may really be, seems to come to us from a 
 luminous or shining point, in straight lines, called rays 
 {radii) of light, which spread from the point in all direc- 
 tions, like radii of a sphere from the centre. It matters 
 not whether the point is bright with its own light, or 
 receives its light from another bright point, and only 
 bends it back, or reflects it, to our eyes. Still we see it 
 by means of rays, which spread from it in all directions, 
 and a certain number of which, called a pencil of rays, 
 enter the round hole in front of the eye, called the pupil, 
 and so enable us to see the point. Thus, from every point 
 of the flame of a candle which we look at, and from every 
 point of a white wall, a pencil of such rays has entered 
 our eye. In the former case, each point is giving forth 
 its own light ; in the latter case, each point in the wall is 
 reflecting to us light which has shone upon it, it may be, 
 from the candle or the Sun. In like manner, every point 
 of the Sun is seen by a pencil of rays of its own direct 
 light ; and so is each bright point in the midnight sky, 
 which we know to be a Fixed Star. But each point of a 
 Moon or Planet is seen by reflected light- — by light which 
 it has received from the Sun, and reflects to our eyes. 
 And so, too, while the Sun is shining, each point of the 
 sky overhead, and of the Earth below, is seen by reflected 
 
FIEST LESSONS IN SCIENCE. 107 
 
 light wliioli has been received from the Sun. Nay, when 
 clouds cover the Sun's face, it is still his light by which 
 we see things in the daytime. His rays escape by the 
 sides of the clouds, and so get reflected from the sky upon 
 the Earth ; and they have power enough also to pierce 
 through the particles of vapour of which the clouds are 
 formed. And so from every object we look at, or rather 
 from each point in every object, from each point of every 
 tree, and flower, and blade of grass, there still comes a 
 pencil of reflected sunlight, stronger or fainter, as it may 
 be, to fill the little opening in front of our eye. Even 
 before the Sun rises, and after he has set, while his 
 disk is still below the horizon, some of his rays strike 
 upward, and are reflected back to us by the sky, and 
 we see what is called twilight. It can be shown that, 
 the nearer we are to the Poles, the longer will be the 
 time of twilight. There is very little of it in tropical 
 countries near the Equator. In such countries, almost 
 as soon as the Sun has gone down, the darkness sets in ; 
 and, in the morning, the first break of day is very soon 
 followed by the rising of the broad disk of the Sun above 
 the horizon. 
 
 68. Thus, then, we see each point of an object by means 
 of a pencil of light, which enters our eye, and then, by 
 the wondrous contrivances of God's Wisdom, there is pro- 
 duced within the eye an exact copy, or image, of the point. 
 And similar pencils from all the other points of the object 
 produce their images too. And so, inside the eye, we 
 shall have an image of the whole formed, very much 
 smaller than the object we are looking at, but an exact 
 copy of it. And the marvel is that ten thousand of such 
 pencils may enter the eye at one moment, coming in 
 various directions, and yet not confuse each other's effects. 
 If you make a hole with a pin in a piece of paper, and 
 
108 FIRST LESSONS IN SCIENCE. 
 
 hold it close to the eye, you may see the whole country 
 round by means of pencils which have passed through 
 that hole into your eye in all directions, and formed their 
 images within it. But here you must observe that you 
 cannot see by a single t&j of light. You must have a 
 pencil of light to enter your eye if you wish to see the 
 point from which it comes. And in that pencil there 
 must be gathered together a certain number of rays in 
 order to produce an effect on our organs of vision and 
 enable us to see the point from which they came. If a 
 bright point be distant, though it is throwing out rays in 
 all directions, yet it is plain that fewer and fewer will fall 
 upon our eyes as we go farther away from it. When we 
 stand far away, the rays, which enter the eye from any 
 point, though they fill the pupil of the eye, will yet be 
 few; they will not be so much crowded together in the 
 pencil as when we stand nearer. In fact, it can be shown 
 that, if we first stand at any distance from the point, and 
 then go off twice, thrice, four times, &c., as far from it, 
 then at the point where we first stood, twice two, or four, 
 times as many rays will enter the eye as when we are 
 twice as far off; three times three, or nine, times as many 
 as when we are thrice as far off; four times four, or sixteen, 
 times as mariy as when we are four times as far off, &c. ; 
 and the point will appear to us four times, nine times, 
 sixteen times, &c., as bright. Hence we may be so far 
 off from a very bright point, that the image formed by 
 the rays which enter the eye from it may only be strong 
 enough to see it very faintly, or may not be strong enough 
 for us to see it at all. 
 
 69. Now, as you have been told, the telescope is a hollow 
 tube, with a glass at each end. These glasses are not 
 common flat glasses, but lenses, as they are called, that is, 
 glasses curved on one side, or both, in a particular way. 
 
FIEST LESSONS IN SCIENCE. 109 
 
 One part of the effect of a telescope is to collect more light 
 from any point of a distant bright object than we can take 
 in with the small pupil of the eye. This is done by a 
 large lens at one end of the tube, which is called the 
 object-glass, and which is turned towards the distant 
 point. It plainly catches a much larger number of rays 
 from the point than the naked eye could catch ; and, by 
 means of its curved form, it has the power also to bend 
 all these rays, so that they all converge, as it is said, or 
 meet together, in one point. This point, in such a tele- 
 scope as Galileo's, is inside the tube, and there these rays 
 form a bright image of that distant point from which they 
 came. The same takes place for every point of the bright 
 luminous object ; and so a bright image is formed of the 
 whole distant object inside the tube. This, then, is the 
 use of the object-glass. Such a glass as this, if held to 
 catch the Sun's rays, will bend them in to form a small 
 image of the Sun. And this will be of such intense heat, 
 because so many pencils of rays are collected by the glass, 
 that it will soon burn a hole in a piece of paper. Hence 
 the place where such an image of the Sun is formed is 
 called a, focus, or fire-place. And the same term is applied 
 to the place where the image of any other object or point 
 is formed by the rays of each pencil being collected in a 
 point. 
 
 70. At the other end of the tube is a lens, or a set of 
 lenses, called the eye-glass. This receives the rays coming 
 from each point of the bright image inside the tube, and 
 bends them again, so that they enter the eye in a fit state 
 to produce clear vision, for the image inside the tube is 
 formed too near the eye to be seen distinctly. You know 
 that any object looks magnified if you put it nearer to 
 the eye ; but, if it be brought too near, you cannot see it 
 clearly, though stiU the nearer it is, the larger it will 
 
110 FIEST LESSONS IN SCIENCE. 
 
 look. So then' this image of the distant object formed 
 ■within the tube being brought so near the eye, would 
 look much larger than the object itself does, if only it 
 could be seen distinctly. Now the eye-glass effects this 
 by bending the rays in each pencil that comes from any 
 point in the image, so that they all enter the eye in a 
 direction nearly parallel to one another, which is the best 
 for clear vision. 
 
 In fact the eye itself is a lens, or, rather, a set of lenses 
 which has power to bend the rays of any pencil which 
 pass through the pupil, and make them all converge to a 
 point. At the back of the eye is a fine network, called 
 the retina ; and if the rays of a pencil converge to a point 
 on the retina, the effect is then carried to the brain by the 
 optic nerve, of which the retina is a part, and the image 
 formed at the point is seen distinctly. If the image is 
 formed at a point behind the retina, the rays will fall upon 
 the retina in a little circular patch as they are converging 
 towards that point. If the image is formed at a point 
 before the retina, the rays will fall upon the retina in a 
 little circular patch after having passed through that 
 point when they are now diverging, or spreading out 
 again. In either case, then, the image will not be seen 
 distinctly as a point. 
 
 71. Now, the more curved the front of the eye is, the 
 stronger will be its power of thus bending the rays of any 
 pencil that enters the pupil. The eyes of most men are 
 so made that they can bend the pencils of rays which 
 come from distant points, such as the Stars, and which 
 come to us nearly in parallel lines, so as to make them 
 converge upon the retina. In other words, most men are 
 able to see distinctly a Star, as a bright point of light. 
 And the eye has also a power given to it, by means of 
 certain muscles belonging to it, of slightly altering its 
 
FIRST LESSONS IN SCIENCE. Ill 
 
 form in front, and making the curve somewhat greater, 
 so as to make a pencil of rays which is coming from a 
 point nearer than a Star, if not too near, converge also to 
 a point in the retina. Thus most men can see clearly a 
 distant ship at sea, or a tree upon a hill, or a bird upon a 
 tree (if near enough for the image formed of it upon the 
 retina to be strong enough to be seen at all), or an object 
 still more close to the eye, as the letters of a book, pro- 
 vided that the book be not held too near. Most persons 
 can read distinctly when the book is held about two feet 
 from the eye. But if they hold it closer, the eye has not 
 power to curve itself enough, so as to cause the rays 
 from each point of the page to converge to a point in the 
 retina. They will form their images hehind the retina, 
 and so these will not be seen distinctly. 
 
 72. This is not the case, however, with the eyes of 
 all persons. Some persons have their eyes too convex, or 
 curved outwardly in front, so that the image of a Star will 
 be formed at a point before the retina, and so they will see, 
 not a bright point, but a little circle of fainter light. And 
 all other objects, which the eyes of most men see distinctly, 
 will appear to these indistinct. But then such persons 
 are able to read a book when held closer to the eye than 
 two feet; and using the power which the eye has of 
 curving itself yet more, they can read the book distinctly 
 when held still closer. Hence such persons are said to be 
 short-sighted. Their sight is excellent for near objects ; 
 but for more distant ones they require the help of spec- 
 tacles, of which the glasses are concave lenses, that is, 
 slightly hollowed or curved inwardly on each side. The 
 effect of these is to make the rays which pass through 
 them converge towards a point farther off than they would 
 otherwise do, so that the very convex eye is now able to 
 bring them to a focus exactly on the retina. 
 
112 FIRST LESSONS IN SCIENCE. 
 
 Others, again, have the fronts of their eyes less convex 
 in front than usual. They can use their muscular power 
 to curve them a little more, and so be able to see distinctly 
 a distant object. But they cannot curve them enough to 
 see distinctly a near object, or to read a book at the usual 
 distance. They must hold a book three feet off, in order 
 to see the letters distinctly; and at that distance, 
 probably, the images will not be strong enough to be seen 
 at all. Such persons are said to be long-sighted; and 
 require the help of spectacles with convex glasses, which 
 help to make the rays converge before they enter the 
 pupil, and then the eye does the rest, and brings them to 
 a focus on the retina. As persons get older, the front of 
 the eye usually becomes less convex ; so that most old 
 persons require the aid of such spectacles. For the same 
 reason, however, short-sighted persons get to see more 
 distinctly, without the help of concave glasses, as they get 
 older. 
 
 73. Let us now return to the Moon. As the Earth 
 attracts the Moon, so too the Moon attracts the Earth, 
 and disturbs its motion about the Sun very slightly. 
 And, in fact, all the Planets attract one another, and more 
 or less disturb each other's motions, as we have seen in 
 the case of Neptune. So that all this shows that they do 
 not exactly move in circles round the Siin, as we have 
 been supposing, though the curves they describe are 
 almost circles. And when it is desired to fix the place of 
 any Planet, as Jupiter, and say in what part of the sky it 
 will be found on a certain day, all these little effects must 
 be taken into account, and it must be seen how much 
 Jupiter is drawn from his proper place in his orbit about 
 the Sun, by each of the other Planets, and in what direc- 
 tion he is drawn. Besides this, we must take into 
 account, what time has passed since the rays, by which 
 
FIRST LESSONS IN SCIENCE. 113 
 
 ■we see him, left the Planet, and during that time he and 
 the Earth have heen moving on. And many other nice 
 calculations of this kind must he made, before we can 
 be sure that we know where the Planet will be on a given 
 day. But in this way its place may be fixed in the sky 
 long beforehand. And this, perhaps, shows, as clearly as 
 anything, the wonderful knowledge which God has 
 now granted to us, far greater than the knowledge which 
 even Galileo possessed, so that, in spite of all such dis- 
 turbing forces and irregular movements, men, who study 
 these matters, are able to fix many years beforehand, and 
 to set down in books for the use of their fellow-men, the 
 places which Jupiter, or any of the heavenly bodies, will 
 have at any precise moment of any future day. Thus 
 every year there is printed in England, by the Queen's 
 Order, a book called the Nautical Almanac, which is meant 
 specially for the use of sailors. And in this book are set 
 down the places of most of the bright or well-known 
 Stars, whether Planets or otherwise — not the places which 
 they had when the book was printed, but those which 
 they will have at the end of five years from that time. 
 
 74. These books are printed year by year continually ; 
 so that ships sailing from England, and expecting to be 
 absent some time, may obtain them for some years to come 
 before they start, and find their way, by their help, across 
 the great deep in safety. For, by looking at the Sun and 
 Stars, sailors are able to direct their path over the wide 
 ocean, though they can see nothing but the sea and sky 
 around them. They are able to make out each day how 
 far they have sailed, and in what direction they have 
 gone. And each day at noon they set down upon a large 
 map a dot of ink, to mark the exact spot in the sea which 
 the ship has reached. Eor this purpose they are very 
 much helped by watching the eclipses of Jupiter's satel- 
 
114 PIEST LESSONS IN SCIENCE. 
 
 lites. And, therefore, in the Nautical Almanac, the exact 
 moment is fixed, five years beforehand, when each of these 
 satellites wUl he eclipsed — not passing behind the body 
 , of the Planet, as seen from the Earth, but passiag into his 
 shadow, as I have said, vs^hich is thrown away from the 
 Sun ; so that, as we cannot see the shadow itself, but only 
 the effect of a satellite entering it, they seem suddenly to 
 disappear at a little distance from the body of their lord. 
 But besides being eclipsed by Jupiter's shadow, they are 
 also occulted, or hidden, by his body, when they pass 
 behind it as it were. The first and second satellites are 
 so near the Planet, that the times of their entering into 
 the shadow (immersion), and coming out of it {em:ersion), 
 cannot both be observed. The satellite, if we have seen 
 its immersion, will be occulted before it emerges ; or it 
 may be occulted when immerging into the shadow, and 
 we can only see its emersion. 
 
 75. This you will easily see by a figure. Draw a small 
 circle to represent the Sun's large body, and at some 
 distance from it draw a much smaller one to stand for 
 Jupiter. Draw two lines touching both circles, so ag 
 to meet when produced in a point behind Jupiter, that is, 
 on the farther side of him from the Sun. Then the space 
 behind Jupiter, between these two lines, will be that of 
 the shadow of Jupiter. No light can reach this space from 
 the Sun, because of Jupiter's body. Now draw a bit of 
 the Earth's orbit around the Sun, and around Jupiter 
 draw a circle to represent the orbit of one of his Moons. 
 Let E be the Earth in any part of its orbit, but so as not 
 to lie between the Sun and Jupiter ; and from E draw 
 lines Ea, Eb, to the points where the orbit of the satellite 
 cuts the lines which bound the shadow. Then the im- 
 mersion will take place at a, and the emersion at 6. Now 
 draw lines Eo, Ed, from E, to touch the body of Jupiter, 
 
To face page lU. 
 
PIEST LESSONS IN SCIENCE. 115 
 
 and to cut the satellite's orbit behind Jupiter in c and d. 
 You will see then that, if the orbit be large, as that of the 
 third or fourth satellite, the immersion and emersion will 
 both be seen from E, the satellite suddenly disappearing 
 from view as it enters the shadow at o, and not being 
 seen again till it comes out of it at 6. Then it will go on, 
 till at c it disappears again, and suffers oocultation while 
 it goes on from c to d, when it has passed behind the body 
 of the Planet, and comes again into view from E. But if 
 the satellite's orbit be a very small one, as that of the first 
 or second satellite, you will see that, if its immersion at a 
 be visible, it will get behind the body of the Planet and 
 be occulted, before it emerges at 6; or, if its emersion at 
 6 is visible, it must have been behind the Planet's body 
 at its immersion. 
 
 76. Sometimes the four are seen in a line on one side 
 of Jupiter, sometimes three on one side and one on the 
 other, sometimes only three, two, or even one can be seen, 
 the others being at that moment eclipsed in the shadow 
 of Jupiter. All four, however, never disappear at the 
 same time, for it is a curious fact that the three inner 
 moons can never be all together on the same side of 
 Jupiter, so that two only can be eclipsed at the same 
 time. The third of these moons, reckoning outwards from 
 Jupiter, is the largest — larger, in fact, than Mercury ; the 
 second is the smallest, a little larger than our Moon. But 
 they are all much smaller compared with Jupiter, than 
 the Moon is compared with the Earth. The nearest of 
 them is about 289,000 miles off from Jupiter, farther off 
 than the Moon from the Earth, but it goes round him in 
 less than two days, fourteen times as fast as the Moon 
 goes round the Earth. If it did not go so fast, the great 
 mass of Jupiter would draw it in to himself. The farthest 
 off of them goes round him in seventeen days, and the 
 
 I 2 
 
116 FIRST LESSONS IN SCIENCE, 
 
 others at lesser intervals. So that eclipses or occultations 
 of one or other of them are almost daily happening. And 
 the times when they will happen, and the places of the 
 Planet, are set down in this book long beforehand with 
 the most perfect accuracy, so that those who travel by 
 land or by sea may tnow when and where exactly to look 
 for them. 
 
 77. Now let me tell you something more of what is 
 known about the nature of the Sun himself, and each of 
 his troop of Planets. You know already the shape and 
 size of the Sun, and his distance from the Earth, But 
 there are one or two other things to be said about him. 
 "When he is looked at with a telescope, by the help of a 
 coloured glass, so that the eye will not be hurt by the 
 glare of his light, there may often be seen upon his surr 
 face certain dark spots or patches, of no regular shape, 
 some large and some small, And these spots, if watched 
 from day to day, are seen to move from the Western side 
 of the Sun's disk to the Eastern, always moving in one 
 direction. Then they disappear, and then, perhaps, they 
 will come into sight again on the same side as before, and 
 pass again over the Sun's face. The time wiihin which 
 any one of these spots is eeen to ajppear on the edge of the 
 Sun's face, pass across, disappear, and appear again, is 
 always the same, about 25J days. Whatever these spots 
 may be, this fact plainly shows that the great globe of 
 the Sun is spinning about on its axis, like the Earth, 
 turning round from West to East once in 25J days. It 
 is found that all the Planets and their Moons turn round 
 upon their axes, from West to East, as the Earth does, 
 with the sole exception of Saturn's satellites, which turn 
 from East to West. 
 
 78, "But what are these spots on the Sun?" We 
 paimot say for certain. But there is great reason to 
 
MEST LESSONS IN SCIENCE, 117 
 
 believe that when we look at the Sun we do not see his 
 real hody, but a bright outer covering of luminous or 
 light-giving matter, which wraps it round, just as the air 
 wraps round the Earth. Perhaps there may be another 
 covering of air inside this, next to the body of the Sun ; 
 and there seems some reason for thinking that there is a 
 third outer wrapper of some airy or gaseous matter. 
 However this may be, it seems almost certain that these 
 spots are hollows in the luminous covering which floats 
 around the Sun's body, made, it may be, by violent 
 storms sweeping across his body underneath, or by other 
 causes which we cannot guess at, and that the dark patch 
 which is seen in the centre of any one of them is a part 
 of the Sun's body, which is just disclosed to us. Around 
 the/cdge of this central black patch is a dark border or 
 fringe. And this is what we might expect if we conceive 
 a vast hollow pit, as it were, with shelving sides sloping 
 down through the luminous stratum towards the body of 
 the Sun. 
 
 79. These spots are always found to lie within two 
 belts or zones, on each side of the Sun's equator. Some- 
 times none will be seen for weeks or months together ; 
 sometimes great numbers will be seen at once. They may 
 be small and numerous, clustered perhaps in groups near 
 one another, and so close as almost to mix. Or a very 
 large one may be seen, as much as 45,000 miles in length 
 and breadth, and such a spot as this may be seen after a 
 time to break up into several small ones. Some have 
 appeared and vanished in less than a day. But most of 
 them are visible for about six weeks ; and one in 1779 
 was seen for six months, disappearing and reappearing 
 several times in that interval. When watched from day 
 to day, or even from hour to hour, they are seen to get 
 larger or smaller, changing their forms by degrees, and 
 
118 FIRST LESSONS IN SCIENCE. 
 
 at last vanishing away, the dark edges closing in upon 
 the black patch, which dwindles to a mere point, and at 
 length disappears altogether, after which the dark part 
 vanishes also. 
 
 Besides these dark patches, the face of the Sun is flecked 
 or mottled over with a numher of minute dark spots, 
 which, when closely watched, are seen to be in a constant 
 state of change, as if the luminous matter were in constant 
 motion. And near the larger spots there are often bright 
 curved and branching streaks, which are best seen towards 
 the border of the disk. 
 
 80. The Sun has been ordained by its Creator to be the 
 great source of light to all the bodies of its system, and 
 also of heat, and hence of motion. By its heat are pro- 
 duced the winds, and that state of the air which brings 
 on thunderstorms and lightning. By the Sun's rays the 
 plants are helped in drawing their needful supplies from 
 the soil and the rain; and the plants support animals, 
 and plants and animals are the food of man, and so he is 
 nourished as well as warmed by the action of the Sun's 
 rays. It is the Sun that has been helping through vast 
 ages in laying up stores of coal for man's use, which, as I 
 hope to show you in another book, are made wholly of 
 vegetable matter. And now by the help of this coal he 
 speeds along his iron roads at the rate of a mile a minute, 
 or churns the briny deep with the wheels of his steam- 
 ship, riding, as it has been said, upon the wings of 
 sunbeams. But what it is which causes the Sun's 
 heat, or its power of giving light to the world, God has 
 not given as yet to mortal man to know. It is one of 
 the secrets which He has not yet been pleased to reveal 
 to us. 
 
 81. Next let me speak of the Moon, which is better 
 known to us than any other heavenly body, being so near 
 
FIRST LESSONS IN SCIENCE. 119 
 
 to US. We can see marks upon it with our naked eyes, 
 though, we cannot see plainly what they are. But by the 
 help of the telescope we can make out distinctly that 
 these are no other than mountains and valleys. We can 
 see the shadows cast by the mountains ; and when the 
 Moon is not full we can see the border, next to the dark 
 part, jagged all along, and notched with deep hollows and 
 marked with sharp projecting points. Sometimes the 
 peak of a high mountain is seen beyond the extreme edge 
 of the bright part, catching the sunbeams and glittering 
 as a bright speck in the midst of the dark field. But all 
 the mountain ranges in the bright p^irt appear shining in 
 the Sun's rays of a beautiful creamy white colour, casting 
 shadows of the deepest black on the side turned away 
 from the Sun, these shadows getting longer or shorter, 
 according to the position of the Moon with regard to the 
 Sun. These mountains in the Moon are very numerous. 
 More than 1000 have been actually measured by the skill 
 of man, by means of the lengths of their shadows, and 
 some have been found to be 23,000 feet high, not much 
 lower than the highest mountains of the Earth. They 
 are most of them cup-shaped in form, and the hollow 
 within the cup is very deep, three or four times as deep 
 as the mountain is high. The larger ones have flat 
 bottoms within the cup, from the centre of which rises a 
 small steep conical hill. In short, we are here looking 
 down into volcanoes which are now burnt out. But the 
 marks of streams of lava can be clearly traced with 
 powerful telescopes. There is no sea, no sign of water 
 in the Moon — no clouds, no sign of an atmosphere. When 
 a star passes behind the Moon, however faint may be its 
 light, it is lost to sight in an instant behind the body of 
 the Moon, which would not be the case if it was sur- 
 rounded by air as the Earth is. For then the light of the 
 
120 FIEST LESSONS IN SCIENCE. 
 
 Star -woTild teoome fainter at first, as soon as it got behind 
 the fringe of air, 
 
 82. But in speaking of what we see in the Moon, we 
 can only speak of this side of the Moon, the side turned 
 towards the Earth. The Moon, indeed, turns round from 
 West to East upon its axis, as the other bodies of the 
 Solar System, and probably all the Stars do. But she 
 turns in such a way that the same face is always turned 
 towards the Earth, and we can never see the other side, 
 except a little bit over the border. For anything we 
 know, the state of things may be different there. But 
 since the Moon goes round the Earth in 27^ days, and 
 always shows the same face to us, it is plain that she 
 must turn round upon her axis once, and once only, in 
 that time. So that any place upon its surface must lie for 
 about fourteen days exposed, without change of day and 
 night, to the glare and burning heat of the Sun, without 
 relief from the cloudy shade or the Cooling breeze. And 
 for the other fourteen days it must be turned away from 
 the Sun, and lie in extreme cold and utter darkness. It 
 seems impossible that any form of life, like those which 
 we see on this Earth, should be found at present in the. 
 Moon. No sign of vegetation has yet been observed — ^no 
 change of the surface, such as might arise from change of 
 season. If there were people in the Moon, the Earth 
 would present to them a splendid object. Its face would 
 appear to them thirteen times as large as the Moon's 
 does to us, and showing phases just the opposite of hers. 
 But, as the Earth turns round each day on its axis, they 
 would see a constant change going on in the appearance 
 of the bright part of the Earth, and see distinctly, when- 
 ever our sky was clear of clouds, the countries on the 
 Earth's surface, as we see the tracts of country in the 
 Moon. Often, about the time of new-moon, when the 
 
FIEST LESSONS IN SCIENCE. 121 
 
 dark face of the Moon would not properly be seen at all, 
 we may perceive it shining faintly with EartJisMne, the 
 light of the full-earth, received from the Sun, being 
 thrown back or reflected upon the Moon, as that of the 
 full-moon is upon the Earth. 
 
 83. Mercury is too near the Sun to be well observed. 
 It is said that Copernicus, living, as he did, among the 
 marshes of the Vistula, could never get a glimpse of this 
 Planet. And, though he can be seen at times, yet we 
 know little more of him than that he is globular, about 
 one-fourteenth of the Earth in size, and showS phases 
 like the Moon. Towards dusk, or before sunrise, this 
 Planet twinkles with a vivid, rosy, light ; and, with a 
 good telescope, it may be seen in the day-time, when not 
 very near to the Sun's place. 
 
 Venus is the most brilliant of all the Planets, her 
 yellowish-bright light being at certain times so bright 
 as to cast a shadow. When she rose in the morn- 
 ing, the ancients called her Phosphorus or Lucifer, the 
 light-bringer, and, when she shone after sunset, they 
 called her Hesperus or Vesper. And such words may 
 often be met with now in poetry. It is, however, the 
 most difficult of all the Planets to be seen distinctly with 
 a telescope. Its intense lustre dazzles the sight. All 
 that can be made out is that its surface is not mottled 
 over with spots like the Moon's, but bright all over, 
 except that there may be slight indications of some 
 parts being rather brighter or duller than others. Also 
 the bright horns and edges of her disk, as seen in her 
 different phases, show the same irregular uneven 
 appearance as in the Moon, though not so distinctly. 
 Prom observing these faint marks, it has been concluded 
 that Mercury and Venus both turn on their axes in about 
 the same time as the Earth. This is very probable, but 
 
122 FIRST LESSONS IN SCIENCE. 
 
 not certain. Most likely we do not see, as in the Moon, 
 the real surface of these Planets, hut only their cloudy 
 wrappers, which, if they are inhabited, may serve to 
 ward off the intense glare of the nearer Sun. To Mer- 
 cury the Sun wUl appear sometimes twice, and sometimes 
 thrice, as large as he does to the Earth ; to Venus, he 
 will seem half as large again as he does to the Earth. 
 
 84. Since the radius of the orMt of Venus is 60 millions 
 of mUes, and that of the Earth's orbit, 96 millions of 
 miles, it will follow that when Venus is nearest to us, 
 her dark side is turned towards us, and we cannot see 
 her at all, unless she happens to make a transit over the 
 Sun's disk. If we draw a circle to represent the orbit of 
 Venus, with the Sun, S, in the centre, and take a point 
 E, outside it, to represent the Earth, then if V represent 
 Venus in her orbit, the angle VES is called her angle of 
 elongation, which is plainly greatest when the line EV 
 just touches the circle. This angle gives ns an idea of 
 the distance on each side of the Sun, to the East or West, 
 to which the Planet can stray, as it were. For Mercury, 
 the greatest elongation is about 29°, for Venus about 47°. 
 Venus appears brightest when her elongation is about 
 40°, on either side of the Sun, between the Earth and 
 her position of greatest elongation. She is very far 
 from being full then; indeed, her phase is that of the 
 Moon about five days old. But when her phase gets 
 larger, she gets also farther away from the Earth : so 
 that this is the position in which she appears brightest, 
 bright enough to cast a shadow at night. The transits 
 of Venus over the Sun's disk are of the utmost import- 
 ance in Astronomy, as by means of them a close 
 approximation can be made to the distance of the Earth 
 from the Sun. They happen, however, very rarely, but 
 always in the beginning of June and December. A 
 
To face page 122. 
 
FIRST LESSONS IN SCIENCE. 123 
 
 transit occurred on June 3, 1769 ; when the chief 
 countries of Europe sent out able astronomers to differ- 
 ent parts of the world to make the proper observations, 
 and an expedition was sent out from England to the 
 island of Tahiti, in the Pacific Ocean, under the famous 
 Capt. Cook. Another transit happened on Deo. 8, 1874. 
 
 85. Mars has a ruddy, fiery, appearance, which appears 
 to arise from a strong red colour in his soil. But this is 
 more remarkable to the naked eye, than when the Planet 
 is seen through a telescope ; and, indeed, the colour is 
 yellowish, rather than red, when so observed. His 
 surface is strongly marked with spots, which, no doubt, 
 are the outlines of continents and seas, the land appear- 
 ing of a dull red, the seas of a greenish hue. At the 
 poles there are bright spots of dazzling whiteness, which 
 are thought to be masses of ice and snow, as they are 
 seen to grow less when the Sun's heat is strongest upon 
 them, and to be largest at the end of the polar winter, 
 which is one long night with Mars, as it is with the 
 Earth. For Mars resembles the Earth in many respects. 
 His axis is inclined to the plane of his orbit nearly at 
 the same angle as that of the Earth to the Ecliptic, and 
 he turns round it in about 24J hours. Hence his seasons, 
 and the changes of day and night upon his surface, will 
 be very much the same in character as on the Earth. 
 But, as his year contains 687 days, being nearly twice as 
 long as the Earth's, his seasons will be nearly twice as 
 long as ours. Mars appears to have an atmosphere also, 
 as the Earth has, through openings in which, by careful 
 long-continued observations, the form of the land and sea 
 have been noted, remaining still the same, whenever they 
 could be observed. He is best seen when in opposition, for 
 we then see his full disk ; and, as he is then also nearest 
 to the Earth, he is, at such times, bright enough to be 
 
124 FIBST LESSONS IN SCIENCE. 
 
 compared witlt Jupiter. More commonly, his fprm is 
 gibbous, as part of his bright face is turned away from us. 
 The breadth of the Sun's disk will appear to Mars about 
 two-thirds of what it does to the Earth, 
 
 86. Omitting the small Planetoids, about which I have 
 said all that you need be told about them, I have next to 
 speak of the great Planet Jupiter, who, when nearest to the 
 Earth, in opposition, is almost as brilliant an object as 
 Venus herself, when not at her very brightest. In fact, 
 Jupiter is, perhaps, at such a time, even more remarkable 
 than Yenus, as he is seen at midnight in full splendour, 
 not dimmed, as Venus is, by the presence of sunlight. 
 He is by far the largest Planet of the System, a thousand 
 times as large as the Earth, and nearly half as large 
 again as all the rest of the Planets put together; and his 
 mass, that is, the quantity of matter in his body, measured 
 by his power of attracting other matter, is three times as 
 great as that of all the others, and disturbs very much 
 the small Planetoids, which are so near him. And yet 
 both in bulk and mass the Sun is more than a thousand 
 times bigger than Jupiter. The surface of Jupiter, 
 when seen through a telescope, appears of a light yellow 
 colour, streaked with a number of belts, fading off towards 
 the edge of the disk. These belts are believed to be open- 
 ings in his cloudy yellowish atmosphere, through which 
 his darker body becomes more or less visible. There are 
 generally two strongly-marked belts, one a little north, 
 and the other south of his equator, while the equator itself 
 seems rather brighter than the rest of the disk. And 
 there are smaller ones nearer to the poles, which change 
 their form much less frequently than the equatorial belts. 
 Spots only, darker than the belts, have been seen in the 
 equatorial regions; and, by watching them, astronomers 
 have found that he is whirled round on his axis in about 
 
FIRST LESSONS IN SCIENCE. 125 
 
 ten hours, an extremely short time if we consider his 
 vast size. In fact, his diameter being 88,000 miles (about 
 ten times the Earth's, or one-tenth of the Sun's), we shall 
 find his circumference at the equator to be nearly 280,000 
 miles ; and, therefore, a point on the equator will be going 
 round at the rate of 28,000 mile an hour, twenty-eight 
 times as fast (12) as a point on the Earth's equator. This 
 is the same as the rate at which the whole body of Jupiter 
 moves in its orbit round the Sun, namely, 30,000 miles an 
 hour, a speed sixty times as great as that of a cannon ball. 
 In consequence of this very rapid rotatory motion, the 
 body of Jupiter is much more flattened at the poles than 
 that of the Earth is. In fact the equatorial diameter 
 exceeds the polar by nearly 7000 miles, and the flattened 
 shape of the Planet is very conspicuous. The day will 
 only be about five hours long in Jupiter ; and his axis is 
 so nearly perpendicular to the plane of his orbit, that the 
 days and nights wiU be almost always of the same length, 
 and there will be scarcely any change of seasons. The 
 four moons of Jupiter are found to show always the same 
 face to their primary, turning on their axes, like our Moon, 
 from West to East, in the same time that they go round 
 him. The nights of Jupiter will be always moonlit, 
 except during eclipses, and there will often be in the sky 
 at the same time three moons of different apparent sizes, 
 and having different phases. But there is a region close 
 to his flattened poles from which not one of his satellites 
 can be seen. The breadth of the Sun's disk will appear 
 at the distance of Jupiter only one-fifth of what it appears 
 at the Earth. 
 
 , The system of Jupiter is a miniature, so to speak, of the 
 Solar System. We can here see on a small scale, and 
 taking place in short times, and all completely within 
 our powers of observation, the same effects 'which take 
 
126 FIEST LESSONS IN SCIENCE. 
 
 place in tlie Solar System on a nrncli larger scale, in the 
 course of ages. 
 
 87. Saturn comes next in order, which, is nearly as large 
 as Jupiter, and is attended by eight moons. But the most 
 remarkahle fact with regard to this Planet is that it is 
 surrounded with three (or, it may be, even more) broad, 
 flat, and very thin rings, having all the same centre, 
 which is very nearly the same as that of the Planet itself, 
 the two outer ones bright with the Sun's light, and the 
 inner one dark, very faint, and almost transparent. They 
 all seem to lie in one plane, and remain parallel to them- 
 selves, as the Planet goes round the Sun ; and they are 
 parted from one another by very narrow intervals, and 
 from the Planet by a much wider one, in which the black 
 sky may be seen. Hence they appear almost as one ring, 
 and are sometimes spoken of as such. This occasioned 
 the strange peculiarity which Galileo noticed in the form 
 of Saturn, and whict his telescope was not powerful 
 enough to explain to him. The body of Saturn also is 
 striped with belts, like those of Jupiter, but broader, and 
 not so strongly marked. One principal belt remains 
 almost unchanged upon the Equator. It is plain that the 
 ring is a solid opaque substance, since it throws a distinct 
 shadow on the body of the Planet, on the side nearest the 
 Sun, and on the other side the ring itself receives the 
 shadow of the Planet. The Planet revolves about an axis, 
 perpendicular to the plane of the rings, in about lOJ 
 hours ; and hence it is, like Jupiter, much flattened at the 
 poles. Its days and nights will be short, as Jupiter's. As, 
 however, this axis is not, like Jupiter's, nearly perpen- 
 dicular to the plane of the Planet's orbit, but bent down, 
 like the Earth's, through a large angle of 27°, there will 
 be changes in the seasons, and changes also in the length 
 of day and night. 
 
FIEST LESSONS IN SCIENCE. 127 
 
 88. As Saturn goes round the Sun, sometimes we see 
 the northern or upper surface of the ring, sometimes the 
 southern or lower, and sometimes the thin edge. This 
 edge cannot be more than from 100 to 250 miles broad, 
 and at so great a distance can only appear like a mere line 
 of light on the body of the Planet, being, indeed, quite 
 invisible except with a very strong telescope. This occurs 
 once in fifteen years, when Saturn, in going round the 
 Sun (which he does in about thirty years), reaches the 
 points in its orbit which correspond to the equinoxes in 
 the Earth's orbit. At such times, having been looking at 
 one side of the rings for fifteen years together, we begin 
 to see the other side, and shall continue to see it for fifteen 
 years. At such times also the ring may be invisible for a 
 short time, because we are looking on the dark, and not 
 on the brightened side of it. It is believed that the 
 surface of the rings is uneven, as if there were mountains 
 upon it. The outer ring revolves round its axis in about 
 10^ hours, the same time as it would take a satellite to go 
 round the Planet, revolving at the same distance as the 
 middle of the breadth of the ring. Probably the inner 
 rings revolve, each in its own time somewhat different 
 from this. The motion of this entire system — the Planet, 
 its rings, and its satellites — is so exactly maintained that 
 all the parts of it keep their proper distance unchanged 
 while together they travel on about the Sun. This 
 revolving motion of the rings, and the fact that their 
 centre is not exactly the same as the centre of the ball of 
 the Planet, can be shown to be necessary, in order that 
 the rings may not be drawn in by the attraction of the 
 Planet, and fall upon its surface. The apparent breadth 
 of the Sun, as seen from Saturn, will be only one-tenth of 
 what it is when seen from the Earth, 
 
 89. We know very little about Uranus, except that he 
 
128 riEST LESSONS IN SCIENCE. 
 
 has six satellites, and that their motions form the only 
 exception to the law which is found to prevail among the 
 bodies of the Solar System, namely, that of being from 
 West to East. The moons of Uranus move in orbitgj 
 which are nearly at right angles to the plane of the 
 Ecliptic (whereas all the other bodies of the System con- 
 fine their movements within the Zodiac, except the small 
 Planetoids), and they move from East to West. At the 
 distance of Uranus, the Sun's breadth will appear only, 
 one-nineteenth as large as it appears at the Earth. The 
 diameter of Uranus is d,bout four tinies that of the Earth. 
 
 Neptune is a little larger than Uranus. The Sun 
 appears to him about one-thirtieth only of the size which 
 it appears to have when seen from the Earth — just, in 
 fact, as large as Venus does, when seen as a morning or 
 evening star. But the light of the Sun at Neptune will 
 be far greater than that of Venus at her brightest ; in 
 fact, both the light and heat which reach Neptune from 
 the Sun will be about a thousandth part of what we 
 receive on the Earth. Neptune's distance from the Sun 
 is 2884 millions of miles, which distance light will travel 
 in about 15,000 seconds, or 4 hours 10 minutes ; so that 
 the Sun will have actually risen and set nearly four hours 
 before he will appear to do so to the people, if any, who 
 live in the planet Neptune, 
 
 90. But are there any such people in Neptune and the 
 other Planets ? This is a question which has been much 
 discussed, and to which no certain reply can be given. 
 Our first impulse will, no doubt, be to suppose that these 
 bodies are inhabited worlds. It is natural to think that 
 the Great Creator has not made aU these wise arrange- 
 ments of moons, and rings, and motions of all kinds, and 
 made them, as it seems .to us, in vain. But if we come to 
 look into the question closely, we shall find much to make 
 
FIRST LESSONS IN SCIENCE. 129 
 
 Tis cautious and humble before we lay down laws to tlie 
 Almighty for the government of his own works. As 
 Galileo said, we shall not be so ready to " measure God's 
 wisdom by our own, as if that only were perfect which 
 we see to be so." The fact is that, though we cannot 
 determine the matter either way, yet as far as we have 
 any positive signs to guide us, they tend to show that the 
 Planets are not inhabited. They certainly show that they 
 are not inhabited by creatures like those of this world. 
 If there are any living creatures there, and such, no donbt, 
 there may be, their natures must be wholly different from 
 any we have to deal with here, and from any we can 
 conceive of. The only body of the Solar System which 
 we can examine thoroughly is the Moon ; and that, we 
 have every ground to believe, is not inhabited. Her 
 surface lies waste and barren, like the streams of lava or 
 of volcanic ashes on the Earth, or like the sands of Africa, 
 where no blade of grass finds root. We can examine 
 portions of the Moon's surface so small as a mile square : 
 but no sign of change, no token of life, animal or vege- 
 table, has ever been discerned in any part of it. As you 
 have been told already, it has no water and no air. In 
 short, it is a mere cinder, " a collection of sheets of rigid 
 slag and inactive craters." 
 
 91. Then, as to the Planets, it is known that though the 
 hulk of Jupiter is so large, yet his mass is vastly smaller 
 than it would be if he were made of matter as dense upon 
 the whole as the matter of the Earth is. Bulk for bulk, 
 he is lighter than the Earth, though his whole mass is so 
 much greater. In fact, Jupiter may be even now a fluid 
 mass, not more dense than water, and this may account 
 for the belts by which he is always surrounded: they 
 may be belts of vapour raised by the action of the Sun. 
 But yet the mass of Jupiter is enormous, and its attrac- 
 
 E 
 
130 FIEST LESSONS IN SCIENCE. 
 
 tion will be very great upon a body at the surface of the 
 Planet. In fact, anything which weighs a pound at the 
 Earth's equator would weigh 2^ pounds at the equator of 
 Jupiter. So that if there are living creatures in Jupiter, 
 of what kind must they be ? Dwellers in the waters, at 
 all events, which would help to bear up their weight. 
 But, beyond these, it is scarcely conceivable what beings 
 could live there. And the same is true in a yet greater 
 degree of Saturn, where the Suns light and heat must be 
 one-ninetieth of what they are on the Earth, and where 
 the matter of the ball must, upon the whole, be much less 
 dense than water. Probably a large portion of the ball, 
 which we see as his, is vapour; and yet his whole mass 
 is large, and the weight of a body on his surface will be 
 much greater than on the Earth. Here too, if we sup- 
 pose that there are inhabitants at all, they must be 
 "floating in their ice-cold water, shrouded for ever by 
 their humid skies." And the same holds good in a yet 
 stronger degree for Uranus and Neptune. From all that 
 we can see of Mars, we have reason to think that he 
 resembles the Earth more than any other Planet, and he 
 may, perhaps, be peopled with inhabitants. Of Mercury 
 and Venus we know very little. But Venus receives 
 from the Sun twice as much light and heat as the Earth 
 does, and Mercury seven times as much. It is hard to 
 suppose the existence in such circumstances of living 
 creatures such as we know of. 
 
 92. We cannot doubt thepower of the Creator to adapt 
 these Planets, or any others, to be inhabited worlds. He 
 may enable animals and plants to live on the surface of 
 Venus, screening them from the Sun's burning rays and 
 glaring light by clouds, which never allow them to get 
 a glimpse of the Sun. Or he may adapt their bodies to 
 live with comfort in the cold, moist, dismal, gloom of 
 
FIEST LESSONS IN SCIENCE. 131 
 
 Uranus or Neptune. Or he may even fit tliem to live 
 upon one of the minute Planetoids, whose attraction is so 
 small that "a man placed on one of them would spring 
 with ease sixty feet high, and sustain no greater shock in 
 his descent than he does on the Earth from leaping a 
 yard." All that can be said is, we have no reason what- 
 ever to believe that He has exerted such a power. The 
 only body of the Solar System, the Moon, which we know 
 well, we are almost sure has no inhabitants now. We 
 have no reason to suppose that it has had any during the 
 ages upon ages which passed away, before the creation of 
 man upon this Earth. It is quite possible, therefore, that 
 the Planets may be in the same state now. At all events, 
 it is quite possible that they may not be inhabited by a 
 race of spiritual beings like man — creatures gifted with 
 reason, and conscience, and will. We, in our poor wisdom, 
 may think it necessary that there should be such beings, 
 in the various bodies which circle round the Sun. " If 
 we had planned the system," as Galileo said, " we would 
 have had it so.'' But God, we know, ordered otherwise in 
 the case of this Earth. For countless ages, for millions 
 and millions of years, this Earth was in being before 
 man was placed upon it. It may be so with the rest of 
 the Solar System. 
 
 93. And, if we are asked for what then were the 
 Planets made, we may answer, with a wise and good man 
 (Coleridge) " perhaps to make dirt cheap " — that is, if 
 they are made for no other reason, they may have been 
 made to show, at all events, how little in the eye of Him, 
 whose Name is Love, and Truth, and Holiness, are mere 
 masses of matter, however vast, or multitudes of living 
 creatures, however fearfully and wonderfully made, com- 
 pared with one living man, made in the very image of his 
 Maker, one who can know God, and glorify Him with a 
 
 K 2 
 
132 FIEST LESSONS IN SCIENCE. 
 
 pure and loving service, whioh sliall begin in this world, 
 and endure for ever. 
 
 Yes! the order of this mighty Universe must he 
 beautiful in the eyes of its Creator. We can fancy, as it 
 were, the glorious orbs of Heaven singing for ever, as 
 they go, in perfect harmony, a song of praise to their 
 Almighty Lord. But let us ever bear in mind this fact, 
 that the voice of one little child, that lisps with reverent 
 lips the words of prayer, makes sweeter music than this 
 in the ears of its Father in Heaven. Let us be sure that 
 the acts of willing, loving, obedience, which God wit- 
 nesses in His children upon Earth — their faithful dis- 
 charge of duty, their patience under sufferings, their 
 meekness under wrongs, their self-sacrificing love for the 
 sake of others, their efforts to overcome some bosom sin, 
 their deeds of manliness and brave resolve in the main- 
 tenance of the truth, or in the defence of some righteous 
 cause, it may be, even unto death — such acts as these, 
 which are the acts of spiritual beings, are more beautiful 
 and blessed in His Sight, who is the Father of Spirits, 
 the God of Eighteousness, and Truth, and Love, than all 
 the hosts of Suns and Stars in the Universe. 
 
 94. Besides the Planets and Planetoids, there appear to 
 be also a multitude of much smaller bodies, which circle 
 around the Sun, and sometimes come in contact with the 
 Earth, striking upon it with great force, when they happen 
 to come within the range of her attraction. There are 
 records of many masses of stone and lumps of iron, which 
 have thus fallen from the higher regions of the air, where 
 they would never have been generated. In 1620, a mass 
 of iron fell from which an Eastern Emperor had a sword 
 forged for his use. On April 26, 1803, thousands of 
 stones were scattered over a district in Normandy by the 
 bursting into fragments of a large fiery globe. Some 
 
FIRST LESSONS IN SCIENCE. 133 
 
 have thouglit that these masses were shot up originally 
 from volcanoes in the Moon, with great violence, and 
 went so far, that the Sun or the Earth got a stronger hold 
 upon them than the small mass from which they came. 
 However, it is now generally admitted that they are of the 
 nature of Planets. And all the fiery appearances, with 
 which they are attended, can be fully accounted for by 
 considering the effect of the amazing speed with which 
 they travel upon the air, which they suddenly enter and 
 condense before them. 
 
 95. " Shooting stars also," says Sir John Herschel, 
 " often followed by long trains of light, and those strange 
 meteors, like great fiery globes, which are seen, not un- 
 commonly, traversing the higher regions of the air — 
 sometimes leaving trains behind which last for many 
 minutes, sometimes bursting with a loud noise, sometimes 
 quietly disappearing — may be regarded as bodies outside 
 our Planet, becoming visible only when in the act of 
 grazing the boundaries of the air. One such meteor, on 
 Aug. 18, 1783, traversed the whole of Europe, frord 
 Shetland to Eome, at the rate of thirty miles a second, 
 at a height of fifty miles above the Earth, with a light 
 greatly surpassing that of the full moon, and a diameter 
 of fully half a mile. It changed its form visibly, and, at 
 last, quietly parted into several distinct bodies, taking 
 parallel courses, each followed by a train of light. 
 
 96. On several occasions shooting stars have been seen 
 in astonishing numbers, "like a shower of rockets, or 
 snow-flakes falling, and brilliantly illuminating the whole 
 heaven for hours together, not in one spot only, but over 
 whole continents and oceans, and even in both hemi- 
 spheres." This grand display takes place usually on the 
 night of Nov. 12 or Nov. 13, though not in every year. 
 And, time out of mind, these days generally, but some- 
 
134 FIEST LESSONS IN SCIENCE. 
 
 times the days before and after, have been so marked. 
 There is also a more certain, though not so brilliant a dis- 
 play, on Aug. 9, 10, and 11, when many large, bright 
 shooting stars, with trains, are almost sure to be seen. It 
 is believed that a stream of meteors is always circulating 
 round the Sun, in a kind of broken ring of many groups ; 
 and that the Earth, going round in her orbit, crosses at 
 these times the paths of these bodies, and now and then 
 comes upon a group of them, but not always. 
 
 97. Hitherto I have been speaking of the orbits of the 
 Planets and Moons, as being actually circles, when not 
 disturbed. But, in point of fact, they are not circles, but 
 curves called ellipses. You may describe an ellipse in this 
 way. Pin down a piece of paper by two pins. Then 
 take a piece of thread, and tie its ends so as to make a 
 loop of string large enough to lie loosely around the two 
 pins. And now, with the point of a pencil inside the 
 loop, stretch out the string upon the paper so as to be 
 tight, and trace a line upon the paper by carrying the 
 pencil round the pins, as far from them as the stretched 
 string allows. The curve, which you will have thus 
 drawn, is an ellipse. And you will see that it is of an 
 oval, or egg-like, shape, longer in one direction than the 
 other. If you put the pins far apart, keeping the same 
 length of string, so that the string lets tbe point of the 
 pencil pass at only a very short distance from the pin at 
 each end of the figure, the ellipse will be a very long one, 
 or, as it is said, an ellipse of great eccentricity. But, if 
 you put the pins close together, it will be an ellipse of 
 very small eccentricity, and very nearly a circle. In fact, 
 by using one pin only, and putting the loop over it, you 
 will draw a circle. 
 
 98. Now all the orbits of the Planets and Moons of the 
 Solar System' are ellipses of very small eccentricity, 
 
FIRST LESSONS IN SCIENCE. 135 
 
 almost circles, except those of Mercuiy and the Planet- 
 oids, which move in longer ellipses, though still not -very- 
 different from circles. It seems as if a large Planet, of 
 -which the small ones are the fragments, had been burst 
 or shattered -with great violence, and so these little 
 bodies -were shot off in all directions, far out of the path 
 -which the unbroken Planet -was taking, and out of the 
 Zodiac itself, -within -which he -was moving. And though 
 the Sun's strong arm dragged them back, and compelled 
 them to go round him still as the rest, instead of running 
 away from him altogether, yet he -was obliged to be con- 
 tent -with letting them go round in these longer ellipses, 
 running off at one part of their course to a greater 
 distance than at others. 
 
 99. But this curve, the Ellipse, is a curve of such 
 importance in Astronomy, that I must tell you something 
 more about it. and explain to you some of its chief proper- 
 ties. Next to the circle, -which, indeed, as you have seen, 
 is a kind of ellipse, it is the simplest of all curves. And 
 on this account it had been closely studied by the ancient 
 philosophers, hundreds of years before it -was kno-wn that 
 the bodies of the Solar System moved in ellipses. When, 
 therefore, the illustrious Kepler, -who lived in the same 
 age as Galileo, first found out this great fact, learned men 
 -were already quite familiar -with these curves and all their 
 beautiful properties. The Almighty Giver of all Wisdom 
 had granted this knowledge already to men, to prepare 
 them for the time when He would be pleased, by means of 
 their fellow-men, like Galileo, Kepler, and others, to reveal 
 to them a fuller knowledge of the wondrous order of His 
 Works. 
 
 100. So now take the pins out of your ellipse, and put 
 the letters S and H to mark the points where they stood. 
 Each of these points is called a focus of the ellipse, for a 
 
136 FIEST LESSONS IN SCIENCE. 
 
 reason which you will understand if you rememher what 
 I told you in (69). For, as the pencil went round the 
 curve, the two lengths of the string in its different posi- 
 tions were like so many rays of light all going to make an 
 image at the points S and H. Now join these points by a 
 straight line, and produce it both ways to meet the curve 
 in A and a. Put C at the middle point of Aa or SH ; and 
 through C draw BGb, perpendicular to Aa, to meet the 
 curve in B and b; and join SB, SB. Take P any point 
 in the curve ; join SP, MP, and OP, and produce PG to 
 meet the curve again in p. 
 
 Then is the centre of the ellipse, about which the 
 whole curve is said to be symmetrical, that is, it has the 
 same form on opposite sides of it ; and all lines, such as 
 Aa, Bh, Pp, drawn through G to meet the curve at both 
 ends, are equally divided at G, so that GA and Ga, GB 
 and Cb, GP and Gp, are equal. Such lines are called 
 diameters of the ellipse, and their halves are radii ; but, of 
 course, in an ellipse the diameters and radii are not all 
 equal, as in a circle. The longest diameter is Aa, which 
 is called the major axis ; the shortest diameter, or minor 
 axis, is Bb. 
 
 101. Now, when the pencil was at P, the string lay in 
 the direction SPH, so that SP and HP together made up 
 the whole length of the string stretched outside the two 
 pins. So SB and HB will make up the whole of that length 
 of string, and therefore either SB or HB is half of it. 
 
 Again, when the pencil was at A, SA and HA made up 
 the whole of that length of string ; but SA is equal to 
 Ha ; and, therefore, Ha and HA, or Aa, is the same length ; 
 and, therefore, AG, being the half of Aa, is equal to SB. 
 
 Once more, the least distance of any point of the ellipse 
 from S will be SA, and the greatest distance will be Sa ; 
 and the mean distance, as it is called, or that which is half- 
 
Tofaeepage 136. 
 
FIRST LESSONS IN SCIENCE. 137 
 
 •way between the greatest and least, is SB, wliich is the 
 same as AC ; that is, the mean distance is half the major 
 axis. 
 
 It is plain that if the whole length of string, Aa, and, 
 therefore, its half, AG, he kept the same, the ellipse will be 
 more or less eccentric, and differ more or less from a circle, 
 according as SH, or its half SC, is greater or less. Hence 
 we shall know how great or small the eccentricity of the 
 ellipse is, if we know what part or fraction the line SO is 
 of the line AC. The number, which expresses this frac- 
 tion, is called the eccentricity of the ellipse. In the orbits 
 of Mercury and many of the Planetoids, the eccentricity is 
 about ^, that is, SO is one-fifth of AC. In the Earth's 
 orbit it is only one-fiftieth, and in that of Venus only about 
 one- tenth even of this, so that her orbit is very nearly a 
 circle. 
 
 102. This then is the real form of the curves in which 
 the Planets and Moons are moving. They are, therefore, 
 sometimes nearer to the Sun, and sometimes farther off 
 than when at their mean distance. But these changes in 
 distance are not very large, owing to the small eccentrici- 
 ties of their orbits, if we take into account their great dis- 
 tances from the Sun. Thus, the Earth's eccentricity being 
 one-fiftieth, SC in her orbit will be one-fiftieth of AG, the 
 mean distance, that is, will be one- fiftieth of 96 millions of 
 miles. Hence SC will be nearly 2 millions of miles ; and 
 SA will be 94 millions, and Sa, 98 millions of miles. Fo 
 that, when the Earth is at A, nearest to the Sun, at her 
 perihelion, as it is called (meaning, about the Sun), she will 
 be nearer the Sun by 4 millions of miles than when she is 
 farthest off at a, at her aphelion (which word means, away 
 from the Sun). Now the Earth reaches her perihelion about 
 the time when she gets to the southern solstice, that is, 
 when it is midsummer in countries south of the Equator, 
 
138 FIRST LESSONS IN SCIENCE. 
 
 or Equinoctial Line, as it is also called. Hence tlie direct 
 rays of the Sun in summer are hotter South of the Line, 
 than North of it. 
 
 103. This great discovery of the orbits in which the 
 Planets move around the Sun, was made, as I have said, by 
 Kepler, and first published to the world by him in 1609. 
 Kepler was a German philosopher, who, though much 
 honoured with the praise and confidence of princes, was 
 left all his life to struggle with poverty, yet patiently and 
 joyfully pursued the work which God had given him to do 
 in this life, of searching into the secrets of nature, and 
 making known to his fellow-men the wondrous truths 
 which he had first been enabled to discover. He was some- 
 what fanciful, indeed, at times, in his notions. For instance, 
 he held, at one time, that the Earth itself was a huge living 
 creature, with passions like those of other creatures, living 
 on its surface. It breathed in volcano blasts ; it trembled 
 or shook itself in earthquakes. " The Earth," he wrote, " is 
 not an animal, like a dog, easily roused or quieted ; but 
 more like a bull or an elephant, slow to become angry, and so 
 much the more furious when enraged." At last, he became 
 closely engaged for many years in considering the motions 
 of the Planet Mars. He found that no scheme which had 
 yet been devised by Astronomers for explaining his move- 
 ments answered to those which really took place. The 
 Planet would not take the position which it ought to have 
 taken, according to calculations made beforehand, in agree- 
 ment with any one of those schemes. He devised other 
 schemes of his own, making calculations with infinite toil 
 to test the truth of each of them. And when one of these 
 scbemes failed him after another, he patiently threw aside 
 his useless papers, and most ingeniously struck out a new 
 one, to spend the same labour over that with the like re- 
 sult. At last — by chance, as it seemed, but as we shall 
 
FIRST LESSONS IN SCIENCE. 139 
 
 surely say, by the gift of God — his wonderful patience and 
 perseverance were rewarded by tbe discoYery of the actual 
 nature of Mars's orbit, and, through that, of the nature of 
 the orbits of all the Planets. Nor was this all. He found 
 out other most remarkable facts connected with their 
 motions, which have since been shown to be true by cer- 
 tain proofs, as well as tested by millions of observations, 
 and upon which, in fact, all those calculations of the 
 Nautical Almanac, before spoken of, are based. These 
 are now handed down to all ages as Kepler's Three 
 Laws. 
 
 104. Before I set down in words these Laws of Kepler, 
 I must explain one or two expressions that will be used in 
 stating them. 
 
 When we say that one thing varies as another, we mean 
 that it is proportional to another, so that, as in (19), if one 
 be doubled, trebled, halved, &c., then the other will have 
 to be doubled, trebled, halved, &c. 
 
 Again, the square of a number is the number obtained by 
 multiplying it by itself, or by taking two such numbers 
 and multiplying them together. Thus 4 is the square of 
 2, 9 of 3, 16 of 4, &c. And the cube of a number is the 
 number found by multiplying three such numbers together. 
 Thus 8 is the cube of 2, 27 of 3, 64 of 4, &c. 
 
 Now Kepler's Three Laws are these : — 
 
 I. Every Planet moves about the Sun, describing a curve 
 in one plane, such that the time of going through any arc 
 of the curve is proportional to the area or space bounded 
 by the arc itself, and lines drawn from the Sun to the two 
 ends of the arc. 
 
 II. The curve, which each Planet describes about the 
 Sun, is an ellipse, with the Sun in one of the two foci. 
 
 III. The square of the periodic time (that is to say, the 
 time in which it goes round the Sun, and which we have 
 
140 FIEST LESSONS IN SCIENCE. 
 
 called the Planet's Tear), is proportional to the cube of its 
 mean distance from the Sun. 
 
 When Kepler had discovered the last of these Three 
 Laws, he broke out into a burst of exulting joy. " It is now 
 eighteen months since I got the firstglimpseof light, three 
 months since the dawn, very few days since the unveiled 
 sun, most admirable to gaze upon, burst out upon me. 
 Nothing holds me : I will indulge my sacred fury. If you 
 forgive me, I rejoice ; if you are angry, I can bear it ; the 
 deed is done, the book is written, to be read now or by pos- 
 terity, I care not which. It may well wait a century for 
 a reader, as God has waited six thousand years for an ob- 
 server." 
 
 106. Thus, supposing the Earth, or any other Planet, to 
 move in its orbit from a to P in any time, say a month of 
 28 days, then, by Kepler's First Law, in the next month it 
 would move on from P to Q, so that the area QSP will be 
 equal to the area PSa ; in the next week, it would move on 
 from Q to iJ, so that the area MSQ is one-fourth of the area 
 QSP or PSa ; in the next day it would move on to T, so 
 that the area TSB is one-seventh of the area BSQ; and so on. 
 
 But the Second Law says that any Planet, such as the 
 Earth, moves in an ellipse with the Sun in the focus. 
 Hence it will be plain that a Planet will move quicker at 
 its perihelion than at its aphelion, in order that the areas 
 described in the same times may be equal. And so, though 
 the Sun's heat is greater, as was shown in (102), at places 
 south of the Earth's Equator during their summer, because 
 then the Earth is at her perihelion, yet her motion is then 
 more rapid, and, therefore, the heat, though greater at any 
 moment, has not so much time to produce its effect upon 
 the Earth. In other words, the Earth itself is not more 
 heated on this account, though a person's face may be more 
 burnt. South of the Line, than North of it. 
 
3b /ace page 140. 
 
FIRST LESSONS IN SCIENCE. 141 
 
 Again, Neptune's distance from the Sun is thirty times 
 that of the Earth ; and so the cuhe of his distance is 27,000 
 times the cube of the Earth's distance. Hence, by the 
 Third Law, the square of his Periodic Time, or Year, ought 
 to be 27,000 times the square of the Earth's Periodic Time, 
 ■which is 1 year; that is (since the square of 1 is 1), the 
 square of the number of years in Neptune's Year ought to 
 be 27,000. Now, Neptune's Year is 60,127 days, or nearly 
 165 years ; and the square of this number, 165, as you will 
 find by multiplying, is 27,225, which is, of course, a little 
 too large, because 60,127 days do not quite make 165 years. 
 The result is near enough, however, to give you some idea 
 of the truth of Kepler's Law. 
 
 106. The discovery by these Laws, which were confirmed 
 after a time beyond all doubt, was a great step in Astro- 
 nomical Science. But something more was needed to com- 
 plete the value of this knowledge, and that was to explain, 
 if possible, the reason of these facts. Kepler had only 
 come upon them, as it were, by chance, by the help of 
 shrewd guesses, and by dint of dogged perseverance. It 
 was reserved, in Grod's good time, for the great English 
 philosopher, Sir Isaac Newton, to bring all the facts under 
 the dominion of one Great Law, which he first announced 
 to the world in 1687, as the Law of Universal Gravitation. 
 This Law I will state to you presently. Let me tell you 
 first the story of the way in which Newton was led to dis. 
 cover it. He was sitting in his garden one day, when an 
 apple fell from a tree upon the ground. He was led to 
 think of the cause which had made it fall, namely, the 
 Earth's attracting force. That force had acted on the 
 apple at the top of the tree, and brought it to the ground. 
 It would have acted upon a cannon-ball fired up into the 
 air, and would have brought that also down. " How high, 
 then," he thought, " must a thing go before that force would 
 
142 FIEST LESSONS IN SCIENCE. 
 
 cease to be felt ? What was there to prevent its being felt 
 at any height ? Why might it not act even at the distance 
 of the Moon ? Might not the Moon, perhaps, be made to 
 go round in her orbit, by having a motion given to her at 
 first, and then being left to be pulled by the Earth's attrac- 
 tion ? " But the Earth and Planets went round the Sun 
 just as the Moon went round the Earth. Kepler had shown 
 this : though neither he nor any one else had thought of 
 their being drawn towards the Sun. But might it not be 
 so after all ? " What if they too were drawn to the Sun by 
 some attracting force ? " 
 
 Such thoughts as these passed through the mind of New- 
 ton as he brooded in deep reflection over the fall of the 
 apple. Doubtlessi they came to him by the gift of Him 
 who is the Father of Lights. The time was come when 
 God was pleased to reveal this farther knowledge of His 
 Works to man. 
 
 107. Newton went to his house, determined to see what 
 he could make out on these points by reasoning on paper. 
 It took him days and weeks to complete the work. But, 
 at last, by a series of ingenious calculations, he showed 
 that each of Kepler's Three Law s was only a necessary con- 
 sequence of One Great Law. 
 
 He shewed that Kepler's First Law proved that each 
 Planet, having first had given to it a motion of its own, 
 was attracted to the Sun by some force or other, always 
 drawing the Planet towards the Sun. 
 
 Again, he showed that Kepler's Second Law proved that 
 this Force must be proportional to what is called the 
 inverse equare of the Planet's distance from the Sun : that 
 is to say, the force, with which the Sun attracts a body at 
 any given distance from it, will be four times as great as 
 it will be at twice the distance, nine times as great as at 
 thrice the distance, sixteen times as great as at four times 
 
FIRST LESSONS IN SCIENCE. 143 
 
 the distance, and so on, the force being always kss as the 
 distance is greater, in proportion to the square of the dis- 
 tance. 
 
 Lastly, he showed that Kepler's Third Law proved that 
 the Sun attracted one Planet just in the same way as 
 he attracted the others, the difference in the pulling force 
 which he exerted on them depending only on their distance 
 from him, not on anything in the Planets themselves. 
 The Sun, in fact, was not a partial lord to his troop of fol- 
 lowers. He had no special interest in Mercury or Venus, 
 more than in Uranus or Neptune. If they were all at 
 the same distance from him, they would all be equally 
 attiacted. 
 
 Finding, then, such reason to believe that the Sun 
 attracted, in this way, with a force varying as the inverse 
 square of the distance, he boldly assumed the Law of 
 Gravitation, namely, that every particle of matter attracts 
 every other particle, with a force varying as the inverse square of 
 the distance. 
 
 108. " Now, if this Law be true," he said, " the Earth will 
 attract the Moon with a strong pulling force, made up of 
 the separate pulls at each of its little particles, and varying 
 as the inverse square of the distance." He could not tell 
 the number of particles in the Earth's mass. But he knew 
 what her pull was upon a particle at her own surface, at a 
 distance of 4000 miles from her centre. He could measure 
 this by the speed that pull would produce in any given 
 time, say one second, in a stone let fall from the hand. 
 That speed, he saw, was the same for all stones, large or 
 small, if they were not too small, so as to be blown about 
 by the wind. He found that, during the first second of 
 time, they would fall about 16 feet, but they would then 
 be moving at the rate of 32 feet in a second ; at the end. of 
 two seconds, they would be moving at the rate of 64 feet 
 
144 FIKST LESSONS IN SCIENCE. 
 
 in a second ; at the end of three seconds, they would be 
 moving at the rate of 96 feet in a second; and so on. In 
 one word, the Earth's pull was adding a speed of 32 feet 
 every second ; and from this he could calculate how far it 
 would be pulled by the Earth's attraction in any given 
 time, say ten seconds, or ten hours, or ten days. But this 
 would be the effect of the Earth's attracting force at the 
 distance of 4000 miles from its centre. Whatwoidd be 
 the effect of it at the distance of the Moon, 240,000 miles 
 off? This distance is 60 times as great as the other ; there- 
 fore, if the Law of Gravitation be true, the Earth's pull at 
 her own surface would be 3600 times as great as at the dis- 
 tance of the Moon ; and the distance, therefore, through 
 which a stone would be drawn at any given time at the 
 Earth's surface, would be 3600 times as great as that 
 through which the Moon would be drawn by the Earth's 
 pull at the same time. Eeasoning thus, with great labour 
 he worked out on paper the motion which the Moon ought 
 to have, and fixed the place where she ought to be found 
 at a certain time. Alas ! the result was, like so many of 
 Kepler's, a complete failure. The place which the Moon 
 really had did not at all agree with the place which he 
 had marked for her beforehand. 
 
 109. Newton was beaten back for a time. Still he was 
 confident that his reasonings, with regard to the motions 
 of the Planets about the Sun, could not be wholly wrong ; 
 and he did not abandon his belief in the Law of Gravita- 
 tion, though he could not account for its failure when 
 applied to the Moon's motion. He put away his papers 
 for the present, and kept his secret to himself for some 
 years, waiting for light to be thrown upon the matter. 
 What I have now told you took place in 1666, when he 
 was only twenty-three years old. Thirteen years passed 
 away before he set himself again to consider these ques- 
 
FIRST LESSONS IN SCIENCE. 145 
 
 tions very closely once more. In 1679 lie worked out more 
 fully upon paper his reasonings for the planetary motions, 
 and was convinced more than ever of their truth, though 
 the difficulty of the Moon's motion remained as before. 
 But how had he come to know the distance of the Moon 
 from the Earth, which was so important an item in his 
 calculations ? He had found this too by reasoning (which 
 I will try to explain to you a little at the close of this 
 book), taking for granted, in order to find it, that he knew 
 for certain the length of the Earth's radius, the distance 
 from her centre to her surface, which was also an item of 
 equal importance in all his reasonings. In that very year, 
 1679, by the good Providence of God, a French philosopher, 
 Picard, made a new and very careful measurement, in order 
 to determine the Earth's radius. Three years afterwards, 
 Newton heard a report of his doing, and of the result he 
 had arrived at, at a meeting of philosophers in England, 
 in the rooms of the Eoyal Society. The length of the 
 Earth's radius, according to Picard's measurement, differed 
 considerably from that which Newton had all along as- 
 sumed to be true. So he went home to go through all his 
 calculations again, with this new fact before him. Every 
 step he took in his work seemed to make it more certain 
 that all his old difficulties would vanish. At last he got 
 so excited with the prospect of such complete success, which 
 was opening more and more before him, that he could not 
 go on with his work for agitation of mind. He was obliged 
 to call in a friend, and beg him to finish the calculations. 
 The result was all he could desire. The Moon took the 
 very places in her orbit about the Earth which he had 
 marked out for her beforehand. And, from that day to 
 this, the Law of Gravitation is admitted by all philosophers 
 to be the Law of the Solar System, and, most probably, of 
 the whole visible Universe. 
 
 L 
 
146 FIBST LESSONS IN SCIENCE. 
 
 108. Tlie Law of Grravitation is, as I have already said, 
 that every particle of matter attracts every other particle of 
 matter with a force varying as ike inverse square of the distance. 
 And Newton showed that it followed from the above Law, 
 that a mass of matter, in the form of a sphere, attracts any 
 particle, on its surface or outside it, just as if the whole mass 
 were collected in one point at the centre. 
 
 The Earth, however, is not exactly, a sphere, but 
 bulges out at the Equator, so that a body at the Equator 
 will be farther off from the centre, than at the Poles. 
 Hence the attraction of the Earth may be expected to be 
 less upon a body at the Equator, than upon a body at the 
 Poles. So that, on this account only, namely, the shape, 
 of the Earth, the same body may be expected to weigh 
 somewhat less at the Equator than at the Poles. But the 
 Earth is also revolving about its axis. And on this ac- 
 count a body at the Equator will be like the stone slung 
 round by a string, that is, it will want to go on in the 
 direction, in which it is moving at any moment, and so it 
 will pull as it were, upon the Earth's hand, and, if it does 
 not fly off, it will be because it is pulled back by the 
 Earth. Hence, part of the Earth's attraction on a point 
 in ihe Equator will have to be spent in counteracting 
 this centrifugal tendency, as it is called ; whereas, at the 
 Poles, the whole attraction of the Earth acts in increasing 
 the weight of the body. And so it is found that, if a body 
 could be taken from the Pole to the Equator, it would lose 
 a small part of its weight in consequence of the Earth's 
 shape, and another small part in consequence of the 
 centrifugal tendency at the Equator ; and, in fact, from 
 both causes, a body that weighs 194 pounds at the Poles 
 would weigh only 193 at the Equator. 
 
 109. Newton also applied the Law of Gravitation to 
 explain the Tides of the Ocean. Suppose, for the sake of 
 
FIKST LESSONS IN SCIENCE. 147 
 
 simplicity, tiiat the ocean wraps the whole Earth round, 
 as a thin film of water. Then the Moon will attract 
 the water on the side nearest to it more then the hody of 
 the Earth, which is farther off, and she will attract the 
 body of the Earth more than the water on the farther side 
 of the Earth. Newton showed that the resrtlt of this will 
 he that the water will tend to form itself into a spheroid ; 
 that is, it wiU lose its form as a spherical shell, and bulge 
 out both on the side next the Moon, and on the side 
 opposite to it or farthest off. If the Moon were at rest, 
 and the Earth did not turn upon her axis, this spheroid 
 would be quietly formed, and, once formed, all then would 
 be tranquilly at rest. But there is no time for the spheroid 
 to be fully formed. Before the waters can so arrange 
 themselves, the Earth will turn round, and so the waters 
 on its surface will pass continually under the Moon, and 
 the same will happen also from the Moon*s own motion. 
 The result will be that an immensely broad and very flat 
 wave will follow after the Moon, as it were, the spheroid 
 trying to form itself all along the surface of the ocean as 
 the Moon goes on, though this effect does not tate place 
 rill about three hours after she has past the meridian of a 
 place. It will be a wave, not a current, that will thus 
 travel along. In other words, it will not be the water 
 itself, but a form, which the water wUl take, that will 
 travel along. Just so, when a stone is thrown into a pool 
 of water, you may see circular waves spreading out from 
 the place where it fell, and travelling towards the border 
 of the pool. Or, when you are in a ship at sea, you may 
 see a huge wave coming along, as if it would swallow up 
 the ship and all ; but when it reaches the ship, the ship 
 will just be lifted up upon it, the wave will pass under it, 
 and be seen on the other side, travelling on as before. In 
 such cases it is the appearance, not the water itself, that is 
 
 L 2 
 
148 FIKST LESSONS IN SCIENCE. 
 
 moving on. The water, in fact, is just being lifted up 
 and down in its place as the ship is ; but this produces 
 an appearance of a wave going on, 
 
 110. Well, then, such a very broad flat wave is caused 
 by the Moon's attraction, and travels on after the Moon ; 
 and, when the higher or lower parts of this wave reach 
 the open coast of a country, it is high or low water there. 
 The Sun by his attraction forms a similar wave. When 
 it is new or full Moon, the Sun and Moon are either on the 
 same or on opposite sides of the Earth ; and, in either case, 
 their efforts will be joined together, and the wave will be 
 increased; and then occur the highest or spring tides. 
 When the Moon is at the end of her first or third quarter, 
 the Sun's tide will be formed at right angles, as it were, 
 to the Moon's, and the two efiects will partly neutralise 
 each other : then we have the lowest or neap tides. 
 
 It is to be observed that the tides are caused by the 
 difference only of the attractions of the Sun and Moon 
 upon the waters and upon the solid body of the Earth. 
 If, for instance, the Sun pulled the water on the nearest 
 side of the Earth, just as strongly as he pulled the body 
 of the Earth, and pulled the body of the Earth just as 
 strongly as he pulled the water on the other side of the 
 Earth, there would be no disturbance, no spheroid formed, 
 and no tide. It is because he pulls the first more than the 
 second, and the second more than the third, and so tends 
 to pull the first away from the second, and the second 
 away from the third, that the solar tide is formed. And, 
 of course, the same is true of the lunar tide. Now the 
 Sun's attraction, either upon the water or upon the Earth's 
 body, is very much greater than the Moon's. But the 
 Sun is so much farther off than the Moon, that he attracts 
 the water on the nearer side of the Earth very little more 
 than the water on the farther side. The difference between 
 
FIRST LESSONS IN SCIENCE. 149 
 
 the Sun's attraction upon the water, and upon the Earth's 
 body, is much less than the difference, in the case of the 
 Moon. Hence the tide caused by the Moon is greater 
 than that caused by the Sun. The two tides, in fact, may 
 be represented by the numbers 5 and 2 ; when joined, the 
 spring-tide may be represented by 7, and when counter- 
 acting each other, the neap-tide may be represented by 3. 
 This however, is only true of the tides in the ocean, or 
 on open coasts, where there are no strong currents. Local 
 circumstances, currents, &c., affect the tides very much in 
 particular places. 
 
 111. But another fact was shown by Newton to be true 
 in connection with these discoveries. He had now made 
 it certain that the Sun did attract all bodies in its System 
 with a force proportional to the inverse square of the 
 distance. And he showed that, in consequence of this, all 
 these bodies, having had a motion given to them at first, 
 which would have carried them on in straight lines, for 
 ever, if they had not been attracted, will now be compelled 
 to travel in a curved line around the Sun, hut not necessarily 
 in ellipseg. He showed that there were two other kinds of 
 curves, which they might move in, as well as ellipses, by 
 reason of the Sun's attraction ; and that whether they 
 would move in one or other of these three curves, would 
 depend entirely on the velocity or speed, with which they 
 were moving. The Planets, be showed, were moving with 
 such velocities, that they must go in ellipses. But the 
 speed, with which a body was moving, when first acted on 
 by the Sun, might have been too great to allow of its 
 going in an ellipse. It might then move in a parabola, 
 or, if the speed were greater still, it would move in an 
 hyperbola. You will be able to form some idea of the 
 shape of these curves in this way. 
 
 Take S for the Sun in the focus, and SA the peri- 
 
150 FIRST LESSONS IN SCIENCE. 
 
 helion distance of a body. Produce SA to E, and draw a 
 line through E perpendicular to EAS. Now draw a 
 curve line through A, such that, if P be any point in it, 
 and PJlf be drawn perpendicular to the line just drawn 
 through E, the distance SP shall be in the same proportion 
 to PM, that SA is to AE. So that, if SA be halfoi AE, 
 then SP must be half of PM ; if SA be equal to AE, 
 then SP must be egwaZ to PM; if S^ be twice AE, then 
 jSP must be twice PM; and so on. The curve so formed 
 will be an ellipse, parabola, or hyperbola, according as SA 
 happens to be taken less than, or eqaal to, or greater 
 than, AE. 
 
 You will see that the parabola and hyperbola are not, 
 like the ellipse, closed curves. A body, going on in either 
 of these, would go on for ever, without returning to the 
 same point again. 
 
 112. Now there are bodies in the Solar System which do 
 move in such curves as these, some in hyperbolas, many 
 more in parabolas, and others of them in very long ellipses, 
 ^so long, that, when they have once passed round the 
 Sun, it may be thousands of years before they will pass 
 round him again. These are the Comets (that is, Hairy 
 Stars), which appear from time to time in the sky, and 
 sometimes are so bright and strange in form, with their 
 long fiery tails, that, like eclipses of the Sun, they are 
 objects of dread to superstitious and ignorant people, who, 
 on seeing them, fancy that some dire calamity is about to 
 happen. Now, however, we know how to explain exactly 
 the movements of these bodies, as we know how to predict 
 the exact time of an eclipse. Some of them, as I have 
 said, move in elliptic orbits of very great eccentricity. 
 They come in, many of them, from distant regions, some 
 from regions far beyond the bounds of Neptune's orbit, 
 aad often come quite olose to the Sun, so as almost to 
 
Tofaoepage 150. 
 
FIRST LESSONS IN SCIENCE. 151 
 
 graze his body, hurrying round him with amazing speed, 
 because they are still bound to obey Kepler's First Law, 
 that of the description of equal areas in equal times. In 
 fact, Newton showed that this Law applies, not only to 
 the Planetary motions, but to orbits of every kind described 
 round any centre of attraction, whether the force varies 
 as the inverse square of the distance, or not. Then they 
 go off again into distant space, to return after a longer or 
 shorter interval, according to thei^ mean distance from the 
 Sun, in obedience to Kepler's Third Law. We can calcu- 
 late their times of return to the Sun, and say when we 
 may look for them, though tens, or hundreds, or even 
 thousands, of years may pass between one perihelion visit 
 of one of these rovers and another. But those which 
 move in parabolic or hyperbolic orbits, will never come 
 back, when once they have passed round the Sun, unless, 
 as they speed along their paths, some one of them should 
 be pulled or struck out of its proper path, by coming 
 near to some other body; and then the direction of its 
 motion might be so changed that it might pass round the 
 Sun again, and, perhaps, ever after go round in an ellipse. 
 This is believed to have happened to one Comet, which 
 came very near the great Planet, Jupiter. 
 
 113. We only see the Comets in that part of their 
 orbits which is close to the Sun. And it is not always 
 easy to decide, from observations taken at this part of the 
 orbit, whether a body is moving in a long ellipse, parabola, 
 or hyperbola. Besides they travel very fast, when so near 
 the Sun, and remain in sight only for a few weeks or 
 months at a time — rarely for so long as a year. However, 
 about 200 of these bodies have been noted with sufficient 
 care to enable us to say that 40 of them move in elliptic 
 orbits, 160 in parabolic orbits or ellipses of very great 
 eccentricity, and seven in hyperbolas. Most of these, and 
 
152 riKST LESSONS IN SCIENCE. 
 
 a multitude of others, can be seen only with telescopes, 
 when they appear as small faint filmy clouds or nehulae. 
 It is believed that there are many thousands of these 
 bodies in the Solar System, and many which do not come 
 near enough to the Sun, at their points of perihelion 
 passage, for us to see them at all. We know of one, in 
 1729, which came no nearer to the Sun than the orbit of 
 Jupiter. And multitudes may not be seen by us, because, 
 when near the Sun, they may be in that part of the 
 heavens which is above our horizon in the daytime. In 
 such a case, a Comet might become suddenly visible, if 
 there occured an eclipse of the Sun. And this actually 
 happened, as we are told by a Eoman writer, Seneca, 
 sixty-two years before the birth of Christ (B.C. 62), when 
 a large Comet was seen near the Sun in an eclipse. We 
 can imagine what an appalling effect this darkening of 
 the Sun, and glaring forth, at the same time, of the 
 Comet, like a flaming sword, must have had upon ignorant 
 people in those days. ' 
 
 114. The motions of the Comets are not, like those of 
 the Planets, confined to the Zodiac. They come rushing 
 in towards the Sun, like messengers from distant parts 
 of his dominions, from all parts of the heavens. North 
 and South, West and East — some going forward, that 
 is, from East to West, as the Planets move, others 
 going hachward, from East to West, with what is called a 
 retrograde motion. Yet they obey still the Laws of 
 Kepler, or that, which includes those Laws, the Law of 
 Gravitation. So that not only the Planets, those Wan- 
 derers, as the ancients called them, but the Comets also, 
 these fiery meteors, which were once thought to rove in 
 perfectly lawless disorder through the heavens, are proved 
 to be under Law, as every thing else is in the Universe 
 of God. Superstitious terror must now give place to 
 
FIRST LESSONS IN SCIENCE. 153 
 
 devout admiration of the Order, which, reigns supreme 
 under his Government, and to a child-like trust, that even 
 other things, which we cannot yet explain and see with 
 our eyes to he governed hy Law — which may seem to 
 us at present irregular and disorderly — are yet held in 
 control hy our Father's Mighty Hand, and are working 
 out the good pleasure of His Will. 
 
 115. Some of these Comets, which are seen by the naked 
 eye, are, certainly, portentous objects, having long tails 
 of light, with which they seem to sweep the skies. But 
 these tails, and the very bodies of such Comets, are seen, 
 upon closer observation, to be nebulous or cloud like, as if 
 they were composed of masses of thin vapour — so thin, 
 indeed, that not bright Stars only, but very faint ones, 
 too faint to be seen at all by the naked eye, can be seen 
 with a telescope through the thickest parts of them, 
 without being the least dimmed. And yet the same Stars 
 would have been quite hidden from sight by a common 
 fog. Great fears have been felt, at times, lest a Comet, 
 in its headlong wild career, should some day dash against 
 the Earth, and shatter it to pieces, or else, at all events, 
 approach so near to it, as to raise 'the waters of the seas 
 on its surface by its attraction, and so produce an over- 
 whelming deluge. All that can be said is, that, as far as 
 we can judge, should such an event ever happen, "it would 
 be a very bad thing for the Comet." As for the Earth, 
 there is little cause to fear from her coming near to such 
 a mass of thinnest possible vapour. All the Comets in the 
 Solar System have not yet sensibly disturbed in the 
 slightest degree the motion of any one of the Planets, 
 however often they must have crossed their paths, and 
 however near they may have come to them. 
 
 116. " But, indeed," says Sir John Herschel, " the largest 
 Comets can only be regarded as great masses of thin 
 
154 FIRST LESSONS IN SCIENCE. 
 
 vapour, penetrated through and through with sunbeams, 
 
 and reflecting the Sun's light from all their particles, as 
 
 a cloud, which floats in the highest regions of the air, and 
 
 seems at sunset to be drenched with light, glowing 
 
 through its whole depth, as if actually on fire. Nay, the 
 
 most light and airy of such clouds must be looked upon 
 
 as dense and massive bodies, compared with the filmy and 
 
 all but spiritual texture of a Comet." It is true, the hulJe 
 
 of a Comet may be enormous. The body of the Comet of 
 
 1811 was 540,000 miles in diameter, more than half that 
 
 of the Sun, to say nothing of its tail. But Newton has 
 
 shown that a globe of common air one inch in diameter, if 
 
 raised 4000 miles above the Earth, would expand of itself 
 
 to fill up a sphere exceeding in diameter that of Saturn's 
 
 orbit. " Hence," says Sir John Herschel, " the whole body 
 
 and tail of a great Comet may consist of only a few pounds 
 
 or even ounces of matter," expanded to an immense bulk, 
 
 and each particle reflecting the rays of the Sun. What 
 
 else, in fact, can be expected, when a Comet approaches 
 
 so near to the Sun, that his heat is felt, like the heat of 
 
 70,000 tropical Suns ? Sir John Herschel says that this 
 
 is twenty-five times as hot as the heat of a very powerful 
 
 lens, which melted rock-crystal. 
 
 When such a Comet first appears, it looks like a little 
 spot of faint nebulous light on the dark ground of the 
 sky. As it draws nearer to the Sun, day by day, it 
 becomes more bright, and the tail begins to show itself, 
 always in a direction opposite to that in which the Sun is 
 situated, behind the Comet, as it were, but not generally 
 lying exactly in the path along which the Comet has 
 come. Brighter it shines and brighter, sometimes bright 
 enough to be seen in broad daylight, and the tail becomes 
 longer and longer, till the Comet often gets so close to the 
 Sun, as to be lost in his beams. After a time it appears 
 
FIRST LESSONS IN SCIENCE, 155 
 
 again on the other side of the Stin, having passed the 
 perihelion. And then it is, after passing the Sun, that a 
 Comet generally shines forth in its greatest splendour. 
 Its tail, which will either have vanished altogether for a 
 time, or else will have twisted around with amazing 
 rapidity, through two right angles, in perhaps two days, 
 so as always to point away from the Sun, will now ac- 
 quire its greatest length and brilliancy, showing that the 
 Sun's heat is really the cause of this strange appendage. 
 The Comet will now begin to move more slowly, and 
 appear more faint, the tail dying away by degrees, or 
 being gathered up, as it were, into the head, which, 
 though feebler, yet, strange to say, will get larger, as the 
 tail gets shorter, this latter being still turned away from 
 the Sun, and, therefore, now being in front of the Comet. 
 At last, from mere faintness of light, the body of the 
 Comet is no longer visible with the strongest telescope, 
 even while its magnitude is still increasing, as appears 
 from observation and calculation, though to the eye it 
 looks smaller with its increasing distance. The tail is often 
 long and straight, sometimes bent into the form of a 
 curve, sometimes parted into two branches. Some have 
 been seen with two tails or more, one with six, spread out 
 like an immense fan. The tail of the Comet of 1843, whose 
 centre was only 97,000 miles from the surface of the Sun at 
 its perihelion passage, was of enormous length, nearly 200 
 millions of miles longer than the whole diameter of the 
 Earth's orbit. And this tail was thrown out from the Comet 
 in the astonishingly short time of twenty daj's. The tail of 
 the great Comet, which Newton observed in 1680, was 
 thrown out to a length of 60 millions of miles in two daje. 
 117. I have said, just now, thrown out, because there is 
 little doubt that the tail of a Comet is a thin hollow coni- 
 cal shell of matter, which has been turned into vapour by 
 
156 FIEST LESSONS IN SCIENCE. 
 
 the Comet approaching so near to the Sun, and is first 
 thrown out towards the Sun from the hody of the Comet, 
 and then driven hack violently by some unknown force of 
 extraordinary power, and so forms the tail. When Halley's 
 Comet appeared in 1835, the tail began to be formed on 
 Oct. 2, by nebulous matter being thrown out violently, in 
 front of the Comet, from its body or nucleus, which had 
 hitherto been faint and small, but suddenly became much 
 brighter. This matter was thrown out, not all at once, 
 nor in one continued stream, but in jets, which came out 
 on the side towards the Sun, but were then turned back, 
 as smoke would be by a current of air. After the first day 
 the matter ceased to be poured forth for several days •, but 
 on Oct. 8 the jets began again more violently than before. 
 In this way, then, the tail of a Comet is made. Being in 
 the form of a conical shell, it looks, of course, brighter and 
 thicker at the edges than in the middle. The increase of 
 size in the body of a Comet, after leaving the Sun, is ex- 
 plained thus : As it draws near to the Sun, the vapour 
 already composing this shell, and other portions of its 
 matter, are changed by intense heat into a pure, trans- 
 parent, and, therefore, invisible gaseous substance. Hence 
 it came to pass that Halley's Comet, at its perihelion, was 
 seen without any tail. But, after passing round the Sun, 
 this rarefied matter, becoming in some measure cooled, 
 appears again condensed in the form of a cloud, and so in- 
 creases the visible bulk of the Comet. When lost sight of, 
 Halley's Comet looked just as it did when it first made its 
 appearance, having the form of a small round nebulous 
 spot, with a bright point inside it. Though it looked so 
 small to the eye, yet that arose from its great distance. It 
 was really, at that time, a globe of vast size ; and in one 
 week only, shortly after it had passed the perihelion, it had 
 increased so as to become forty times as large as before. 
 
FIRST LESSONS IN SCIENCE. 157 
 
 Many, however, of the brightest Comets have had very 
 short and feeble tails, and a few great Comets have had 
 none at all. 
 
 118. There are some famous Comets, which have been 
 seen again and again in times gone by, and have been 
 taken note of by the writers of those days. One of the 
 most remarkable of these is Halley's Comet, above men- 
 tioned (one of the retrograding Comets), so called from the 
 philosopher of that name, who observed it in 1682, when 
 it appeared in great splendour. Seeing good reason to be- 
 lieve that it was the same which had appeared also in 1531 
 and 1607, so that it seemed to have a period of about 75 
 or 76 years, he predicted that it would appear again in 
 1759. As the time drew near, astronomers were keenly on 
 the watch for it. Clairaut, a great French philosopher, 
 went through a long series of most complicated calcula- 
 tions, based upon the truth of Kepler's and Newton's Laws, 
 to see how much it would be disturbed on its way by the 
 attractions of the larger Planets. He found that Saturn 
 would retard its return by 100 days, and Jupiter by 518 
 days. And, taking due account of these, he announced 
 that the Comet would pass its perihelion within a month 
 before or after the middle of April 1759. It actually did 
 so on March 12 of that year. The next return of this 
 Comet was fixed by two astronomers for the year 1835, 
 one naming Nov. 11, the other Nov. 26, for its perihelion 
 passage. They had now taken into account the exist- 
 ence of the Planet Uranus, which had been discovered 
 in the interval, but not, of course, that of Neptune, 
 which was not yet known. The Comet actually passed 
 its perihelion on Nov. 16 in that year. This shows how 
 accurate are the reasonings of astronomical science, and 
 how sure is the action of the Law of Gravitation, 
 even when applied to these bodies, which are liable to 
 
158 FIRST LESSONS IN SCIENCE. 
 
 meet with, so much disturbance in their extravagant 
 courses. 
 
 119. Encke's Cotaet goes round the Sun in about 3^ 
 years, and it is remarkable for its period being a little 
 shortened every time it goes round. This shows, accord- 
 ing to Kepler's Third Law, that its distance from the Sun 
 is getting smaller by degrees — by very slow degrees, in- 
 deed, but yet so that it seems likely that the Comet will 
 at last fall into the Sun. It is thought that there must be 
 some very rare matter, filling the regions through which, 
 it travels, and by a slight resistance to its motion pro- 
 ducing this effect. And, in fact, there is a remarkable 
 appearance, called the Zodiacal lAglit, which may, perhaps, 
 explain this. This light may be seen on any clear evening, 
 soon aft^r sunset in spring, and just before sunrise in 
 autumn; but it is seen best in tropical countries. It 
 resembles a cone of light, reaching from the horizon 
 upward in the direction of the Ecliptic. Sir John Herschel 
 believed it to be a conical envelope of the Sun, reaching 
 beyond the orbit of Mercury and Venus, even to the Earth's 
 orbit, and that it may be the very matter which retards 
 the motions of the Comets. 
 
 Biela's Comet has a period of 6f years, and, on its 
 appearance in 1846, astonished astronomers by suddenly 
 parting into two Comets, which travelled on, side by side, 
 at about a distance of 160,000 miles from each other. At 
 first, the old Comet got fainter, and the new one got 
 brighter, till it looked sharp and clear as a diamond-spark. 
 Then the new one faded, and the old one recovered its 
 brightness, till it sparkled also as the other. At last the 
 new one disappeared, and the old one after it. All the 
 while, there was a thin bright line passiag from one to 
 the other, seeming to proceed from that which was brightest 
 at the time. After the new one had disappeared, the old 
 
FIRST LESSONS IN SCIENCE. 159 
 
 Comet threw out ttree faint tails, one of wliich pointed to 
 the place where its companion had been. 
 
 There are other Comets, with periods of from 5 to 8 
 years ; and several which describe long ellipses, in periods 
 of from 60 to 80 years. That of 1811, which was visible 
 for months, shining like one of the brightest stars, and 
 with a beautiful fanshaped tail, will not be seen again for 
 3000 years. One appeared in 1844, which at its aphelion 
 distance must have been 142 times as far off from the Sun 
 as the Planet Neptune. This is the longest elliptic orbit 
 that we know of at present in the Solar System. The 
 Periodic Time of this Comet is about 100,000 years. And 
 yet even this hody only travels a fiftieth part of the distance 
 between our Sun and the nearest of the fixed Stars. Once 
 more we are thus made to see, and, perhaps, begin to 
 feel in some measure, how separate, and alone by itself, 
 our little System stands in its awful vacancy. But how 
 comforting it is to know that we may rest secure, under 
 the shadow of the Mighty Hand. 
 
 120. On turning a telescope to the sky at night, a mighty 
 host of Stars will come into view which were too faint to 
 be seen at all by the naked eye, but are now made visible 
 by the larger pencils of rays which the object glass catches, 
 and bends in, so as to form images in the focus of the tube. 
 These images, as you have been told, are formed too near 
 the eye to be seen distinctly. But the eye-glass takes the 
 pencils of rays which come from them, and bends them sb 
 that they may enter the eye in a state fitted to produce 
 clear vision ; and thus the object is not only seen more 
 bright, but seems to be brought nearer to the eye, and 
 magnified. When seen through a telescope, each Planet 
 has a round disk ; and, indeed, with a powerful telescope, 
 Jupiter may be made to look as large as the Moon does to 
 the naked eye. But no telescope has ever yet been mad* 
 
160 FIEST LESSONS IN SCIENCE. 
 
 of sufficient power to show any one of the Fixed Stars, 
 even the nearest of them, with a sensible disk. They 
 appear, when seen by the telescope, as fine bright points of 
 light. Indeed, they look smaller, and look more truly as 
 points, when seen by the telescope, than they do when 
 seen by the naked eye. For, when we look at a Star with 
 the naked eye, the eye is affected in some way, so that 
 there is a certain appearance, which is often represented 
 on paper by rays, spreading from the Star on all sides. 
 This is cut off by a good telescope, and we see only a bright 
 point like a diamond-spark. And when the Moon passes 
 before such a Star, she occults it in a moment ; the lustre 
 of the Star is instantly extinguished, which would not be 
 the case if it had any sensible disk. This is the first inti- 
 mation we get of their vast distance from us, namely, the 
 fact that the most powerful telescopes do not seem to bring 
 them any nearer to our eyes, so as to exhibit a sensible 
 disk. The Stars often seem to twinkle, but this arises from 
 the state of the air. In the clearer skies of the tropical 
 regions, they may often be seen without any sign of 
 twinkling. 
 
 121. The Stars, which can be seen by the naked eye, in 
 the whole heavens, do not exceed about 6000. They are 
 divided into six Classes, according to their brightness. 
 There are reckoned to be about 22 Stars of the First Class, 
 50 or 60 of the Second, 200 of the Third, &c. It is certain 
 that the brightest Stars are not always the nearest. For 
 instance, Sirius, the brightest of the Stars, is known to be, 
 for reasons which I will explain presently, four times as 
 far off as the nearest Fixed Star. Still it is taken for 
 granted that the fainter Stars are, generally speaking, 
 more distant than the brighter. The light of a Star of 
 the Sixth Class is about one-hundredth of that of one of 
 the First Class. But it would take 300 or 400 Stars of 
 
FIRST LESSONS IN SCIENCE. 161 
 
 the Sixth Class to make up the light of Sirius. These 
 6000 Stars, which are seen by the naked eye, have been 
 formed, as yon have been told, into groups or constellations, 
 from some fanciful resemblance to certain figures. And 
 the Stars of each group being numbered, or marked by 
 letters, can be easily referred to. 
 
 But the telescopic Stars are in countless numbers. They 
 are divided into ten Classes, from the seventh to the six- 
 teenth. Of the seventh Class more than 10,000 have been 
 registered. But it has been computed that 20 millions of 
 Stars can be seen by a large telescope. Sir W. Herschel 
 once counted 60,000, which passed before him during one 
 single hour's observation of a very small strip of the sky. 
 But they are not by any means spread equally in all direc- 
 tions over the face of the sky. In some parts of the sky 
 they lie very thickly crowded together ; in others only a 
 few will be met with if the telescope is turned to them ; 
 in others, none at all. 
 
 122. There is one great zone or belt of the sky, which 
 runs all round the heavens, almost in a circle, in which 
 Stars are so thickly crowded that the whole looks to the 
 naked eye, like a trail of milky whiteness drawn across the 
 nightly sky. This is the Galaxy or Milky Way (from the 
 Greek word gala, milk), which was first seen by Galileo to 
 consist of nothing but Stars. It forms, as I have said, a 
 sort of belt all round the sky, but is parted at one point 
 into two branches, which remain separate for a long dis- 
 tance, and then reunite ; and, besides, it sends off, here and 
 there, other minor branches. 
 
 Now, what is this Galaxy of Stars, which plainly has 
 some special relation to our Sun, since we find ourselves 
 thus in the middle, as it were, of this belt. Besides which, 
 there is something more to be noticed as to the way in 
 which the Stars generally are spread about the sky. You 
 
 M 
 
162 FIRST LESSONS IN SCIENCE. 
 
 may remember Galileo's words : " God has just shaken 
 them out of His Hand, as it were, as if by chance. And 
 we, poor simple creatures, must be thinking that He has 
 scattered them up yonder without order or beauty ! " 
 Galileo was right. They seem to be strewed about, " as it 
 were, by chance." But, on looking more carefully, it 
 appears that after all there is an order in their arrange- 
 ment. If a circle be drawn round the sky, through the 
 middle of the Milky Way, as nearly as it can be done, it 
 is found that, as we go Northward or Southward from this 
 circle (which is called the Galactic Circle), the Stars get 
 more and more scarce as we get farther off. But they are 
 somewhat more numerous on the Southern side of the 
 Galactic Circle than the Northern. Thus, suppose we 
 make six belts of the sky, of equal breadth, 15° on each 
 side of the Galactic Circle, then the average number of 
 Stars, which will be seen in a small circular space of a 
 certain size, will be as follows, within the first, second, 
 third, &c., of these belts : — 
 
 Belt. 
 
 Northern. 
 
 Southern. 
 
 1 
 
 53 
 
 59 
 
 2 
 
 24 
 
 26 
 
 3 
 
 11 
 
 14 
 
 4 
 
 8 
 
 9 
 
 5 
 
 5 
 
 7 
 
 6 
 
 4 
 
 6 
 
 123. Now, all the above appearances are explained by 
 supposing the Sun to be in the middle of a cluster of Stars, 
 in the form of a flat bed, of immeasurable breadth on all 
 sides, but not in comparison of great depth or thickness. 
 So, when we look along the breadth of the cluster in any 
 direction, we see Stars innumerable, crowded, as it seems, 
 faint and bright ones together, but these fainter ones being 
 in reality in general the more distant ones, which are seen 
 
FIRST LESSONS IN SCIENCE. 163 
 
 * in the open spaces between the nearer and brighter ones. 
 In other words, if we look along the breadth of the cluster 
 in any direction, we see the Milky Way. If, however, we 
 look in a slanting direction, on either side, we see fewer 
 Stars, and fewer and fewer as we look more away from the 
 direction of the breadth ; till at last, if we look on either 
 side in the direction of the depth, we look very soon, as it 
 were, out of the cluster into the dark abyss of space, and 
 see very few Stars. Yet in these dark openings between 
 the Stars in the Galaxy, may be seen, far away in the dis- 
 tance, faint cloudy spots or nebulse, which may be each of 
 them clusters of millions of Stars, like the Galaxy itself. 
 It is difScult to conjecture the exact form of our cluster as 
 it would appear when seen from a distance — if looked at, for 
 instance, with a telescope from one of those far-off nebulse ; 
 since we are thus placed inside it, and looking out upon it 
 from all parts of the Earth. 
 
 124. You will, perhaps, understand the above more 
 clearly if you imagine yourself standing in the midst of a 
 wood of tall trees, not choked up with undergrowth, but 
 so growing that you can see clearly between the trunks of 
 the trees. If you suppose the wood to be somewhat cir- 
 cular, then you will have an idea of our position when we 
 look at the Stars of the Milky Way, for you will see the 
 trees crowded around pretty equally on all sides, but it 
 will be difficult to judge what the exact form of the wood 
 is on the outside. If, again, you suppose the wood to have 
 a much greater length than breadth, you will see that 
 the trees seem thicker together when you look along the 
 length, but much thinner when you look along the breadth. 
 And, in this case also, it will be difficult to judge of the 
 exact form of the wood as it will be seen by one outside of 
 it. One thing is clear, that the cluster is not exactly of 
 the same breadth everywhere, for then we should see the 
 
 M 2 
 
164 FIEST LESSONS IN SCIENCE. 
 
 Galaxy having nearly the same brigjitness all round. In 
 some parts of it this is the case for immense tracts. But 
 in other parts, rich patches are closely clustered, separated 
 by spaces which are thinly occupied, and are sometimes, 
 indeed, quite dark, void even of the smallest telescopic 
 Star. When we look at these dark places, we are looking 
 through the starry bed which surrounds us into the vast 
 abyss of space. But, whatever may be the exact shape 
 of the cluster, it must be, generally, a mass of Stars, of far 
 greater length and breadth than thickness ; and its thick- 
 ness lies in the North and South direction. 
 
 125. The Sun is placed in the middle of this bed, but a 
 little nearer to the Northern surface of it than the Southern ; 
 and on this account we see the Stars in the Milky Way 
 more crowded when we look at the Southern portion of it. 
 [n other words, the Milky Way will appear brighter when 
 we gaze at it in the Southern Hemisphere, than in the 
 Northern. The place of its nearest approach to the South 
 Pole is near the Southern Cross, which constellation it 
 enters by a very bright and narrow neck, and immediately 
 spreads itself out into a broad, bright mass. In the midst 
 of this bright mass, surrounded by it on all sides, occurs a 
 singular pear-shaped cavity, called from its shape the coal- 
 sack. In this large space only one very small Star can be 
 seen by the naked eye. It contains, however, many tele- 
 scopic Stars, so that its striking blackness must arise from 
 the contrast with the brightness all around it. 
 
 This, then, is the cluster of Stars to which our Sun be- 
 longs. These millions of bright bodies are aU his brethren, 
 glorious Sun as he is, having, very probably. Planets re- 
 volving about them as he has, but so* small that they are 
 not seen at that distance, just as our own Sun's troop of 
 Planets will be invisible to them, and he only be seen as 
 the representative of the whole Solar System. 
 
Tofacepage 165. 
 
FIRST LESSONS IN SCIENCE. 165 
 
 Sir W. Herschel thouglit that the thickness of this bed of 
 Stars was about 80 times the distance from us of the nearest 
 Fixed Stars. Its extreme length he estimated at 250 times 
 the breadth. In that case the light of one of the most dis- 
 tant Stars of the Sun's own family would take 6500 years 
 in coming to us, moving at the rate of 200,000 miles be- 
 tween two ticks of a clock. 
 
 126. But how do we feel so certain of the immense dis- 
 tance of the Fixed Stars from us ? If you were walking 
 along a straight path BC, through the wood we were just 
 now speaking of, and fixed your eye upon a tree A, some 
 little way off on one side of the road, you would see it 
 constantly changing its place with respect to the other 
 trees behind it. Thus, at B, you would see it in the direc- 
 tion BA produced, in a line (suppose) with the more dis- 
 tant tree T. Whereas, when you get to G, you would see 
 it in the direction CA produced, to all appearance having 
 gone backward, and now in a line (suppose) with the tree 
 K. Now, the two lines BA, CA, contain an angle between 
 them, the angle BAG, which angle is called the parallax, 
 or change-of-place angle, for the point A, in consequence 
 of the spectator changing his place from B to G. It is 
 plainly the angle, which the line BG subtends at the dis- 
 tant point A. The farther off the point A is, the smaller 
 will be the angle BAG. And, if it be very distant indeed, 
 compared with the length of the line BG, the lines BA, 
 GA, will meet at a very small angle indeed, and seem to 
 be almost parallel. 
 
 127. Now the size of this angle BAG, may he easily 
 known without going to the point A to observe it. 
 
 (1) Note that, if any line AB meets another line CD in 
 the point B, the two angles, ABC, ABB, are either two 
 right angles, or are together equal to two right angles. 
 
 For if ABC be equal to ABD, each of them is a right 
 
166 FIEST LESSONS IN SCIENCE. 
 
 angle, and the two together are two right angles. But, if 
 ABGhe less than ABD, draw BE at right angles to CD. 
 Then the two angles, ABC, ABD, are made up of the three 
 angles, ABC, ABE, EBD, which make up the two angles 
 EBG, EBD, and these are two right angles; that is, ABC, 
 ABD, are together equal to two right angles. 
 
 (2) Note that, if ABC he a triangle, and BC he pro- 
 duced to D, the angle AGD is equal to the two angles ABC, 
 BAC; and the three angles of the triangle, ABC, BAC, 
 ACB, are together equal to two right angles. 
 
 For draw GE parallel to AB. Then, since BA and CE 
 are parallel, or run in the same direction, the line AC, 
 which crosses them, must make equal angles with each of 
 them ; that is, the angle BAC is equal to the angle ACE. 
 [In fact, if BA be produced to F, and CA to G, the angle 
 BAC is equal to the angle GAF or AGE.^ Again, because 
 AB is parallel to GE, the line BD, which crosses them, 
 must make equal angles with each of them ; that is, the 
 angle ABC is equal to the angle EGD. Hence the angle 
 AGD, being made up of the two angles ACE, EGD, is equal 
 the two angles BAG, ABC. And the three angles of the 
 triangle, BAC, ABC, ACB, are together equal to AGD, 
 AGB, that is — hj what has just before been shown in (2) 
 — they are together equal to two right angles. 
 
 128. So then, returning to the tree A in (126), when 
 the spectator is at B, let him observe the angle ABC, 
 which can be easily done with a proper instrument ; and, 
 when he gets to C, let him observe the angle AGB. Then, 
 if he subtracts the number of degrees in these two angles 
 from two right angles, or 180°, the remainder will be the 
 number of degrees in the angle BAC. Or, if instead of 
 observing at G the angle AGB, he observes the angle AGH, 
 which AG makes with BC produced, then, since the angle 
 AGH is equal to the two angles ABC, BAG, it appears 
 
To face page 166. 
 
FIRST LESSONS IN SCIENCE. 167 
 
 that, by subtracting tlie number of degrees in ABG from 
 the number of degrees in AGH, he will obtain, as the re- 
 mainder, the number of degrees in BAO. 
 
 129. Now, when A is a, Fixed Star, and BO is the 
 longest possible line we can find, so as to be able to look 
 at the Star from the two ends of it, the two lines BA, CA, 
 are found to be absolutely parallel. There are a few 
 exceptions to this, as I will show you presently. But, 
 speaking generally, such is the case. The two angles 
 ABC, BCA, are found to be exactly equal to 180° ; or, in 
 other words, the angle AOH is found to be exactly equal 
 to the angle ABC. There is no diiference between them, 
 so far as the most powerful instruments can detect. Of 
 course, there must be a diiference ; since, however far oif ' 
 the Star A may be, the lines, BA, GA, as they meet at last, 
 cannot be actually parallel. But the difference is so minute 
 that the human eye, aided by the most delicate instru- 
 ments, cannot perceive it, except, as I have said, in the case 
 of some nine or ten of the Fixed Stars. It appears to us as 
 if the lines drawn to the Star from the two ends of the 
 line BG were absolutely parallel. And this is the case, not 
 only when we stand at the two ends of one of the Earth's 
 diameters, so that the length of BG is 8000 miles, but 
 even when we stand at the two ends of one of the dia- 
 meters of the Earth's vast orbit, so that the length of BG 
 is nearly 200 million of miles. The lines of direction in 
 which a Star is seen from the Earth at all seasons of the 
 year, in Spring and Autumn, Summer and Winter, are to 
 all appearance identically the same. The Stars seem to 
 rise and set always in the very same points of the sky, 
 and to keep the same positions with respect to one another, 
 when observed at all points of the earth's orbit. In other 
 words, the Fixed Stars, with very few exceptions, have no 
 sensible parallax. The angle, which the diameter of the 
 
168 FIEST LESSONS IN SCIENCE. 
 
 Earth's orbit (-BC in our figure) subtends at a Fixed Star 
 (^A) is so small, that it cannot be detected at all, and may 
 be reckoned as notbing. 
 
 130. Now, let us see wbat this fact implies. Take A 
 the centre of a circle of large radius, and let BD be that 
 arc of the circle, whose length is equal to the radiiis, and 
 which contains, therefore, 57° 17' 4.5", or 206,265 seconds. 
 Take BG, a very minute arc of the circle, and draw the 
 radii AB, AG, AD. Now it is plain that when AB is very 
 great, and the angle BAG very small, the straight line 
 BG will differ very little, when compared with the great 
 length of AB, from the curved line, or circular arc, BG. Por 
 instance, if AB represent 200 millions of miles, the arc 
 BG may be greater than the straight line BG by a few 
 hundred miles. But that is as nothing compared with 
 200 millions. So we may take the straight line BG to 
 represent the arc BG for our present purposes. Now we 
 know by (19) that, in the same circle, angles at the centre 
 are proportional to the arcs which subtend them. Hence, if 
 the angle BAD be ten thousand times the angle BAG, so 
 will the arc BD, that is, the radius AB (which is equal to 
 the arc BD), be ten thousand times the arc BG, or the 
 straight line BG. 
 
 Suppose now the angle BAG to be 1" ; then since the 
 angle BAD is 206,265", and is, therefore, 206,265 times the 
 angle BAG, it follows that the arc BD, or the line AB, 
 is 206,266 times the line BG. If the angle BAG be one- 
 tenth of 1", the line AB will be ten times the above ; if the 
 angle BAG be 10", the line AB will be one-tenth of the 
 above. So, if the angle BAG he J", ^", &c., AB will be twice, 
 thrice, &c., the above ; or if the angle BAG be 2", 3", &c., 
 AB will be one-half, one-third, &c., of the above. 
 
 131. Hence, if BG represents the diameter of the Earth's 
 orbit, about 200 millions of miles, and the angle BAG he 
 
Tofasefagem- 
 
FIRST LESSONS IN SCIENCE. 169 
 
 tke parallax of a Fixed Star, when seen from the two ends 
 of the diameter, should the Star's parallax, that is, the 
 angle which the diameter of the Earth's orbit subtends at 
 the Star, be as much as 1", still the distance of the Star 
 from the Earth, AB, would be 206,265 times £G, that 
 is, more than 200,000 times 200 millions of miles, or 40 
 billions of miles. Or should this angle of parallax be 
 doubled — in other words, should the angle which the 
 radius of the Earth's orbit subtends at the Fixed Star be 
 1" — still the distance of the Star would be 20 billions of 
 miles ; and light travelling at the rate of 200,000 miles a 
 second, would take 3 J years to traverse that distance. Now 
 the Star called Alpha Centauri is found to have such a 
 parallax as this, the radiiis of the Earth's orbit subtending 
 nearly an angle of 1" at that Star. Hence this Star is about 
 20 billions of miles distant from the Earth. It appears 
 also from this, that, if the Earth's whole orbit were filled 
 with the body of our Sun, so that his diameter, instead of 
 being 880,000 miles, or nearly a million of miles, were in- 
 creased to nearly 200 millions of miles, this vast diameter 
 would still subtend only 2" at this Star. To the naked 
 eye, at that Star, the Sun would appear as a bright point 
 only, as a distant Star, though with a powerful and delicate 
 instrument he might be seen to have a very minute disk. 
 132. Eight other Stars have been found, which have a 
 parallax less than that of this Star. The radius of the 
 Earth subtends at Sirius an angle of ^" ; he is therefore, 
 though so very much brighter, four times as far off as 
 Alpha Centauri, and light takes 13 years to come from 
 him. From Arcturus light comes in 26 years, from the 
 Polestar in ,48 years. None of the other Fixed Stars have 
 been found as yet to have any parallax. And yet our in- 
 struments are so fine that an angle of a thousandth part 
 of 1" might be detected. 
 
170 FIEST LESSONS IN SCIENCE. 
 
 I have said that no instrument can detect a disk with 
 any one of the Fixed Stars. This wonld seem to imply 
 that Alpha Centauri is less in size than our Sun, because 
 the Sun, as we have just seen, would have a minute disk, 
 when observed from that Star. For the same reason our 
 Sun may even be larger than Sirius. . But at the distance 
 of the Fixed Stars, generally, our Sun's diameter would 
 subtend too small an angle to be detected, as their 
 diameters do when seen by our eyes. Hence we can 
 make no comparison of size. We can only say that they 
 must shine, as glorious suns, with intense light of their 
 own, to be seen at all at such immense distances. 
 
 133. But, by means of their parallax, we can find, 
 without ^difficulty, the distances of the Sun, Moon, and 
 Planets from the Earth, and by means of their distances, 
 we can find also their diameters. 
 
 First, in order to this, we must know the diameter of 
 the Earth itself. This is found by measuring with the 
 most careful accuracy the length of one degree on its 
 surface, making all due allowance for the irregularities of 
 hill and dale. But a rougher calculation will answer our 
 present purpose. It is enough if I can show you how we 
 may get some distinct idea of the size of the Earth's great 
 body. We may assume, for reasons which you have been 
 told already, and specially from the form of the Earth's 
 shadow thrown upon the Moon in an eclipse, that the 
 Earth is in shape a globe, as the Sun and Moon and 
 Planets are seen to be. 
 
 Draw a circle to represent the Earth ; and at a point A in 
 it, suppose a white rod AG, to be fixed in the middle of still 
 water, in a vertical position, so as to be in the same line 
 as AB, the Earth's diameter, and to project eight inches 
 above the surface of the water. - Then, if a person goes 
 a mile off to D, and places his eye at the surface of the 
 
TofOAXpage 1?1. 
 
FIEST LESSONS IN SCIENCE. 171 
 
 water, looking through a telescope, he will just see the 
 top of the rod, and no more. The whole eight inches 
 will be hidden from his sight by the Earth's curved form. 
 And, as he is looking along the surface of the water, he 
 will look in the direction of a line touching the circle at 
 D ; that is, the direction of the line CD, in which he sees 
 the top of the rod, will just graze or touch the circle at D. 
 Now it can be shown, from a property of the circle, that 
 the line GB contains CD just as often as CD contains CA. 
 But, since CA is so very small, only eight inches, CD is 
 very nearly the same as AD, that is, CD is one mile, or 
 636,360 inches, so that CD contains CA nearly 8000 times. 
 And, therefore, OB or AB (since CA is only 8 inches,) 
 contains CD 8000 times; in other words, AB is about 
 8000 miles. 
 
 134. Now then, by means of observations made at 
 opposite ends of the Earth's diameter, as in (128), it 
 is found that the Earth's diameter (BC) subtends at 
 (A) the centre of the Sun, an angle (BAG) of 17", that is, 
 the parallax of the Sun's centre, as seen from opposite 
 points of the Earth's surface, is 17". Hence, by (130), the 
 distance of the Sun from the Earth is one-seventeenth 
 of 206,265 times 8000 miles, or one-seventeenth of 
 1,650,120,000 miles, that is, it is about 96 millions of miles.* 
 
 Also, the Earth's diameter is found to subtend at the 
 Moon's centre an angle of 1° 54' 4", or 6844". Hence the 
 distance of the Moon from the Earth is obtained by 
 dividing 1,650,120,000 miles by 6844, that is, it is about 
 240,000 miles. 
 
 135. Again, the diameter of the Sun's disk subtends to 
 our eyes at the Earth an angle of 31' 30", or 1890"- Take 
 
 * This distance must now be somewhat reduced ; but the question, 
 in spite of the observations made at the transits of Venus, is by no 
 means settled, the approximation now made ranging between 92,000,000 
 and 93,000,000. 
 
172 FIRST LESSONS IN SCIENCE. 
 
 this now, as the size of the angle BAG in our figure in (128). 
 If it had been only 1", we should have obtained BG, the" 
 Sun's actual diameter, by dividing AB (the Sun's distance, 
 or 96 millions of miles), by 206,265, that is, we should 
 have found BG to be about 465 miles. But, since the 
 angle BAG iB 1890", hence BOis 1890 times 465 miles, or 
 about 880,000 miles. 
 
 Lastly, the diameter of the Moon's disk subtends to 
 our eyes* an angle of 31' 15", or 1875". If this were 
 only 1", BG would be obtained by dividing 240,000 
 miles (the value of AB, the Moon's distance from the 
 Earth), by 206,265, that is, BG would be about 1-16 mile. 
 Hence, since the angle BAG is 1875", the Moon's diameter 
 will be 1875' times 1-16 mile, or about 2175 miles. 
 
 In like manner, may be found the distances and dia- 
 meters of the different Planets. And, knowing their 
 distances from the Earth, those who understand such 
 matters can easily calculate their distances from the Sun. 
 
 136. Having found the diameters, we now know the 
 size of the Sun, Moon, and Planets. But of what kind of 
 matter are they composed ? Are they heavy or light in 
 proportion to their size? The Sun, for instance, we now 
 know to be a globe of enormous bulk. But is he only a 
 huge globe of light vapoury matter like a Comet, weigh- 
 ing half-a-pound or so, or is he made of heavy matter as 
 the Earth itself? * This is a very important question; and' 
 we are able to give an answer to it. We are able to de- 
 termine the mass of each body, compared with the Earth's 
 mass, that is, we are able to calculate the quantity of 
 heavy matter which each contains, attracting other matter 
 and producing weight, as the matter of the Earth does, 
 though we cannot say whether such matter is solid or fluid. 
 
 It is not easy to explain how this is done. It will be 
 enough for you to know that the Earth, for its size, is 
 
riEST LESSONS IN SCIENCE. 173 
 
 rather lighter than Mercury, rather heavier than Venus, 
 or Mars, or the Moon, nearly four times as heavy as 
 Jupiter, or Uranus, or the great Sun himself, and eight 
 times as heavy as Saturn or Neptune. 
 
 137. You will remember that the Earth's form is not 
 exactly spherical, but spheroidal (spherelike), flattened at 
 the poles, and bulging out in the parts about the Equator. 
 Now, since the force with which any particle attracts, is 
 proportional to the inverse square of the distance from the 
 attracted particle, and the whole mass of the Sun (or 
 Moon) attracts as if it were collected in the centre of the 
 Sun (or Moon), it is plain that its pull upon the protuber- 
 ant part of the earth nearest to it, will be greater than 
 upon that farthest off. If you draw a figure as in (31), 
 representing the Earth in its position of June 21, with its 
 axis bent towards the Sun on the North side of the 
 Ecliptic, you will see that the pull of the Sun upon the 
 bulging part, which lies below the Ecliptic, must be 
 greater than on the bulging part, which lies above the 
 Ecliptic. The result of this is found by experience to be, 
 what philosophers can show beforehand it must be, 
 namely, that the Earth's axis would be moved a little out 
 of the fixed position, parallel to itself, which we have 
 supposed it to keep all along, as the Earth goes round the 
 Sun. And a similar slight disturbance of its position will 
 take place at all parts of the Earth's orbit. In point of 
 fact, the Earth's axis describes, in the opposite direction 
 to that in which the Earth revolves, a small conical sur- 
 face, just as the spUl of a tee-to-tum will do, when not 
 upright, so that its end, produced upwards to the sky, will 
 describe a very small circle in the heavens. This motion 
 indeed, is so extremely small that it takes 25,868 years to 
 go once round in this circle. Hence, for all ordinary 
 purposes, we may suppose the Earth's axis to remain 
 
174 FIRST LESSONS IN SCIENCE. 
 
 parallel to itself, as before, while the Earth goes round the 
 Sun, once, twice, or even a hundred times. But, in the 
 course of a long time, and when delicate calculations are 
 to be made, it is important to notice this fact, and the 
 more so as the axis goes on moving always in the same 
 direction, however slowly, and therefore, the effects pro- 
 duced are continually accumulating. 
 
 138. Now the most obvious result of this motion of the 
 axis is that the Stars, when looked at, after long intervals 
 of time will seem to have moved. For the point, where 
 the Northern end of the Earth's axis meets the heavens, 
 is that which we regard as the North Pole; and, if the 
 place of that point is changed, of course, the Stars, though 
 really fixed in their places, will seem to have moved. Thns 
 the Polestar, which is now so near the place of the North 
 Pole, that it serves almost to mark it, was eight times as 
 far off, that is, it was distant from the Pole 12°, when the 
 first catalogue of Stars was made by Hipparohus. It will 
 still get a little nearer, and then go off slowly, and, after 
 12,000 years, the Star Alpha Lyra3, the brightest in the 
 Northern Hemisphere, will be nearest to the Pole. The 
 Star Alpha Draconis was the Polestar 4000 years ago, 
 when, it is supposed, the great pyramids of Egypt were 
 built at Gizeh. And it is a curious fact, noted by Sir 
 John Hersohel, that, of the nine pyramids at (jcizeh, six 
 (including all the largest), have the narrow passages, by 
 which alone they can be entered, and which open out on 
 the northern face of the pyramid, inclined downwards to 
 the horizon at such an angle, as to allow the then Polestar 
 to have been seen at the bottom of every one of these pas- 
 sages, as it passed the meridian. 
 
 139. But there is another remarkable effect of this mo- 
 tion of the Earth's axis. It will cause the Equinoxes, the 
 points of the earth's orbit, where the Sun is vertical over 
 
FIEST LESSONS IN SCIENCE. 175 
 
 the Equator, to go backward slowly along the Eoliptii 
 very slowly, indeed, so as to go round completely in the 
 same long interval of 25,868 years. But as this change 
 also goes on continually, the effect becomes considerable 
 after a long time. Tou will see that something of this 
 kind takes place, in consequence of this motion of the 
 Earth's axis, if you draw the figure of (35) to represent 
 the Earth at the Equinox of Sept. 21. For, if you now 
 suppose the end of the Earth's axis moved away a little, 
 perpendicular to the plane of the paper, you will see that 
 the Equator will be lifted up a little above the Ecliptic, 
 and the Sun will no longer be vertical at the Equator, 
 but at some little distance South of it. Hence it 
 wiU have already been vertical at the Equator, be- 
 fore the Earth got to this point of its orbit. In other 
 words, the Equinox will have gone backward a little, as 
 it were, to meet the Earth. The time of the Earth reach- 
 ing the Equator will precede a little the time, at which it 
 would have reached it but for this fact. Hence the re- 
 gression, or going backwards, of the Equinoxes, is often 
 called the Precession of the Equinoxes. 
 
 Similar effects are caused by the Moon's attraction, as 
 well as the Sun's ; and these are calciilated separately, as 
 Solar Precession and Lunar Precession. The effects thus 
 produced in one year are very minute indeed. Still, when 
 continually accumulating, age after age, very minute 
 effects become considerable. And the whole retrograde 
 motion of the Equinoxes, which is only about 50" a year, 
 has amounted to about 30° altogether since the first cata- 
 logue was made. The consequence is that when the Earth 
 gets to the Equinox in our days, we no longer see the 
 Sun among the same Stars as Hipparchus did. Instead of 
 seeming to enter the constellation Aries, for instance, at 
 the times of the spring Equinox in northern regions, he 
 
176 FIBST LESSONS IN SCIENCE. 
 
 •will seem to be about to enter Pisces. Nevertheless, 
 astronomers still keep the name Aries for that part of the 
 heavens, in which the sun is seen for about thirty days 
 after this Equinox, though he is really moving all the 
 while through the constellation Pisces. Hence that part 
 of the heavens is called the sign Aries, to distinguish it- 
 from the constellation Aries ; and so it is with the other 
 signs and constellations. 
 
 140. But you will remember also that the Earth does 
 not go round the Sun in a circle, but in an ellipse, and is, 
 therefore, nearer to the Sun at some times than at others. 
 Hence the action of the Sun and Moon on the protuberant 
 parts of the Earth is not quite the same at all parts of the 
 year. Sometimes the Earth's axis is bent a little more to 
 the Ecliptic, and sometimes a little less, than it is in its 
 mean position. This effect is called the Nutation, or 
 nodding, of the Earth's axis. There is, as before, both a 
 Solar and a Lunar Nutation ; and the result is, that in- 
 stead of the Earth's axis describing a little circle in the 
 sky, it describes a wavy line, nearly a circle, but going in 
 and out of that circle continually. This effect, however, 
 is not like that of Precession, continually accumulating. 
 
 Hence it will be seen that, if we wish to determine 
 accurately the place of a star or other heavenly body, so 
 as to compare our observation of it with observations 
 made at another time, it will be necessary to take account 
 of each of these two effects of Precession and Nutation. 
 
 A small correction, as it is called, must be applied on 
 both accounts, in order to fix the body's place in the sky, 
 not as it is now, but as it was, at some particular time, or 
 epoch, which astronomers may agree to fix on, so as to 
 refer all their observations to it. 
 
 141. Besides these two corrections for Precession and 
 Nutation, there are three others, which must be applied in 
 
FIRST LESSONS IN SCIENCE, 177 
 
 every case, before we can determine accurately the place 
 of a heavenly body from the observations we have made. 
 One of these is that for Refraction. The spherical coating 
 of air which surrounds the Earth, acts just as a curved lens 
 does, in bending any ray of light which falls upon it 
 from any distant luminous point, so that the direction in 
 which we see the ray, and in which we, therefore, fancy 
 we see the point from which it comes, is not that in which 
 the point really lies. In fact the air, which is more dense 
 close to the Earth, and gets thinner and thinner, till, at a 
 distance of about fifty miles from it, it does not even exist, 
 may be regarded as consisting of a great many thin coats 
 or shells of different densities. When the ray reaches the 
 outer one of these, it is bent a little, a little more at the 
 next, and so on, till it has travelled along a sort of curved 
 path, before it actually reaches the eye. In consequence 
 of this, the heavenly bodies seem to be higher than they 
 really are in the sky. And a small correction has to be 
 applied in consequence. Indeed, near the horizon the air is 
 so loaded with vapours, that the refraction is considerable. 
 The whole disk of the Sun or Moon is so much raised in 
 consequence that we may see it above the horizon, when 
 it is still below it ; and the lower parts of the disk are 
 more raised than the higher, so as to give a flattened ap- 
 pearance to the lower side of it. Hence twilight is due 
 not only to the reflection of sunlight from the upper 
 regions of the air, but also to the refraction of a portion 
 of the Sun's light, which is curved round to shine upon 
 the clouds, and so be reflected to the Earth. 
 
 142. Another correction is that to be made iot parallax. 
 We observe the body from some point on the surface of 
 the Earth. And, as every observer will do the same from 
 the station where he stands, it is desirable, in order 
 to be able to compare the different observations, that 
 
178 FIKST LESSONS IN SCIENCE. 
 
 they should all be referred to one point, namely, the 
 Earth's centre. A correction then has to be made for this 
 change of place in the point whence the observation is made. 
 
 Lastly, a correction must be made for aberration. Sup- 
 pose a shower of rain to fall perpendicularly, when the 
 air is quite still. If a person were to stand upright, he 
 would be sheltered from the drops, which would fall on 
 his bat. But, if he runs on, he will feel the drops strike 
 on his face. It will seem to him as if they were driven bj' 
 a wind in a slanting direction. And yet, all the while 
 the drops are still falling perpendicularly down, and 
 the appearance arises from his own motion. The same 
 would be true, if there was a little wind at first blowing 
 the drops against his face in a slanting direction, while he 
 himself stands still. As soon as he begins to run, the 
 drops will appear to come in a more slanting direction 
 still ; and, if he supposed them actually to be coming from 
 the direction in which they seem to come, he would make 
 a great mistake. Just so it is with the rays of light, 
 which come from a distant body, as a Star. They seem 
 to come in a certain direction, when they reach the eye. 
 But we are ourselves moving forward with the Earth in 
 her orbit about the Sun, at the rate of 68,000 miles an 
 hour. Hence we must not conclude that the rays, by 
 which a Star is seen, come really from the direction in 
 which they seem to come, even when we have made the 
 correction for Eefraction. We must apply a correction 
 for the aberration of a Star, that is, its " wandering away " 
 in appearance from its true place, by reason of our motion. 
 
 Thus in reducing (as it is called), that is, bringing into 
 order with other observations, an observation of a Star, 
 its place, as shown by the instruments, must have Jive 
 distinct corrections applied to it — those for Befraction, 
 Parallax, Aberration, Precession, and Nutation. 
 
To face page Ha. 
 
FIEST LESSONS IN SCIENCE. 179 
 
 Such is the extreme nicety required in astronomical 
 calculations. But, when these precautions are taten, the 
 point, where a Planet will be seen at any instant, or 
 the line in which Mercury or Venus will cross the disk of 
 the Sun, or the moment at which any given Star will 
 cross the meridian of a place, may be fixed years before- 
 hand, and observed to happen according to the prediction 
 with the most perfect accuracy. 
 
 143. A sidereal day is the interval of time between two 
 successive passages of a Star over the meridian of any 
 place. This is absolutely the same at all times of the 
 year for all Stars ; and it is the day always used by 
 astronomers. For common purposes, however, it would 
 not be convenient, because the business of life is governed 
 by the Sun. Hence a solar day, or the interval of time 
 between two successive passages of the Sun over the 
 meridian of a place, is the day used in common or civil 
 purposes. This day is longer than the former by about 
 four minutes. This arises from the fact that, in the 
 interval, the Earth will have gone on in its orbit about 
 the Sun, and will have to turn rather more than once 
 completely round on its axis before the Sun will come 
 again on the meridian of the place. Thus take S the 
 Sun, and A the centre of the Earth at any part of its orbit. 
 Draw a small circle around A to represent the Earth, and 
 join SA, cutting the circle in P. Then, when the 
 Earth's centre is at A, the Sun will be on the meridian at 
 P. Suppose that, while the Earth turns once round upon 
 her axis, her centre gets on to a ; then, drawing ap 
 parallel to AP, p will be the present position of P. But 
 the Sun is not on the meridian of p ; and the Earth will 
 have to turn round a little more, before p will be brought 
 round for the Sun to pass over its meridian. A Fixed 
 Star, however, if seen from the Earth, on the meridian of 
 
 N 2 
 
180 FIRST LESSONS IN SCIENCE. 
 
 P, in the direction PS when the Earth is at A, wonld, in 
 consequence of its vast distance, be seen in the direction 
 ps at a, on the meridian oi p. 
 
 This small interval of time, by which the solar day 
 exceeds the sidereal, is not the same at all parts of the 
 year, partly by reason of the change of position of the 
 Earth's axis, through Precession and Nutation, and partly 
 by reason of the difference of speed, with which the 
 Earth travels at different points of her elliptic orbit. 
 Hence the solar day is sometimes longer, sometimes 
 shorter, than its mean value. On this account the solar 
 day would be inconvenient for ordinary purposes, 
 
 144. For common purposes, the mean solar day is used, 
 which is equal in length to the average of true solar days 
 throughout the year. This mean solar day is divided 
 into 24 equal parts called hours, the hour into 60 minutes, 
 and the minute into 60 seconds ; and these are the days, 
 hours, minutes, and seconds, shown by ordinary clocks 
 and watches, and employed in common life. The time 
 before noon is marked, as we have seen before, by the 
 letters A.M. {ante meridiem, before midday), that after 
 noon, by the letters P.M. (post meridiem, after midday.) 
 The hour of noon, or midday, is not, therefore, always 
 the time when the Sun is on the meridian. Sometimes 
 the clock may point to twelve at noon a few minutes 
 before or after the Sun comes to the meridian; and in 
 such cases it is said that the clock is before or after the 
 Sun, respectively. The number of minutes, which must 
 be taken from or added to mean-time or clock-time, in 
 order to get the true time, is called the *' Equation of 
 Time," and is set down in the almanacs. Four times in 
 each year the equation of time is zero, that is, the mean 
 time is the same as the true time. 
 
 The sidereal day is 3 minutes 56 seconds shorter than 
 
FIRST LESSONS IN SCIENCE. 181 
 
 the mean solar day, and, therefore, contains 2Sh. 56ni. 4s. 
 of common time. But astronomers use a sidereal clock, that 
 is, a clock which keeps sidereal, instead of common time. 
 They divide the sidereal day into 24 hours (each hour, of 
 course, a little shorter than a common hour), and the hour 
 into sixty minutes. And they consider the day to begin 
 ■when the first point of Aries (that is, of the sign Aries)^ 
 is on the meridian. 
 
 145. The sidereal year is the interval of time, during 
 which the Earth goes round in her orhit about the Sun ; 
 in other words, it is the interval of time between the Sun's 
 being seen from the Earth in a certain position among the 
 Fixed Stars, and his being seen again in that position. 
 That interval is 365d, 6h. 9m. 10s. of mean solar time. 
 This, as I have said, is the time which the Earth takes to 
 make one complete revolution around the Sun. But this 
 is not exactly the time between her leaving an Equinox 
 and returning to it, which is a somewhat shorter interval, 
 because the Equinox, as we have just been seeing, goes 
 backward slowly to meet the Earth, by reason of Preces- 
 sion. This makes the year only 365d. 5h. 48m. 60s. long, 
 and, thus reckoned, it is the time, which passes between 
 the same seasons coming over again. This is what is 
 called the Tropical year; and it is the year used for 
 common purposes, as, of course, it would be very incon- 
 venient for the seasons not to come always at the same 
 parts of the year. Thus, if we took the sidereal year, 
 which is longer than the tropical by 20m. 20s., then 
 supposing that the Sun was in the Spring Equinox at noon 
 on March 21 of any year, the next year this would happen 
 20m. 20s. before noon, the next 40m. 40s. before noon, and 
 so on. In fact, in 60 years, it would happen 20h. 20m. 
 before noon of March 21, that is, it would happen 8h. 20m. 
 before midnight of March 20. And so, in the course of 
 
182 FIEST LESSONS IN SCIENCE. 
 
 years, the day of the Sun being in the Equinox would go 
 back into February, January, December, &c., and we should 
 have spring, and the other seasons, occurring at all parts of 
 the year. By using the tropical year for common purposes, 
 the seasons always happen at the same parts of the year. 
 146. Tou will see, however, that this year does not con- 
 sist of an exact number of days. It contains nearly, but 
 not quite, 365d. 6h., or 366J days. In the days of Julius 
 Caesar, the Eomans used to reckon the year as containing 
 355 days only ; and then their priests and rulers added as 
 many days as they thought necessary to keep the seasons 
 straight, till, at last, utter confusion arose in their 
 reckonings. Julius Caesar, advised by an eminent astro- 
 nomer of those days, Sosigenes, took 365J days, as the 
 length of the year, and ordered that each year should in 
 future be held to contain 365 days, except every fourth 
 year, and that should contain 366 days ; so that the four 
 years together contained the same number of days as four 
 years each of 365 J days. In order to get the seasons 
 straight, he was obliged to order that the last year, before 
 the new system was to begin, should consist of 445 days. 
 Well might this year be called, as it was, the " year of 
 confusion." In order to make up the 365 or 366 days, 
 Julius Cassar ordered that there should be twelve months ; 
 and that, instead of each month containing 30 days 
 (which would ma'ce up only 360 altogether), all the odd 
 months, that is, the first, third, fifth, &c., should contain 
 only 29 days. The seventh month was called Julius, in 
 honour of his name, and we still call it July. His nephew 
 and successor, Augustus, had the name of the eighth month 
 altered after his own name, and we still call it August. 
 But he would not let the number of days in his month be 
 less than in Julius Cesar's. So he made the eighth month 
 to contain 31 days, and changed the rest after it, so as to 
 
FIRST LESSONS IN SCIENCE. 183 
 
 contain in order 30, 31, 80, 31, days. And the day, which 
 he. thus added to the eight month, he took away from 
 February, which was now to contain only 28 days in com- 
 mon years, and 29 in leap years. 
 
 147. The above arrangement we still retain. But 
 Julius Csesar's correction, you see was a little too large, 
 since the year falls short of 365d. 6h. by 11m. 10s. Hence 
 in 60 years this error amounted to llh. 10m. ; and in 360 
 years to 67h., or nearly 8 days. In the year 1414 it began 
 to be perceived that the Equinoxes were gradually creeping 
 away from March 21 and Sept. 21 ; and in 1582, Pope 
 Gregory ordered Oct. 5 to be called Oct. 15, by which the 
 disorder of the calendar was partly set right. I say 
 partly, because if the error was 67h. in 360 years, it would 
 be more than 4 times as much in 1582 years, and 4 times 
 67h. is 268h., or lid. 4h. The correction was made in 
 England in 1752, when Sept. 3rd was changed to Sept. 14. 
 It ought to have been changed to Sept. 15 ; and then all 
 would have been right, with one small adjustment which 
 Gregory also made. In 860 years we have seen the error 
 is 67h., and in 40 years, therefore, rather more than 7h. ; 
 hence in 400 ( = 360 and 40) years the whole error is rather 
 more than 67h. and 7h., or 74h., that is, it is rather more 
 than 3 whole days. If, then, 3 days be omitted in the 
 course of 400 years, the error will be set right, except for 
 the very small error which still remains, and which will 
 not amount to one day in 4000 years. Hence the rule is 
 to reckon every year as a leap year, when the number of 
 the year can be divided without remainder by four (which 
 gives every fourth year,) but not to reckon as leap years 
 the years which close the centuries (as 1700, 1800, 1900), 
 when the number of the centuries (17, 18, 19) cannot be 
 divided exactly by 4. 
 
 148. We will now return to speak of the Fixed Stars. 
 
184 FIRST LESSONS IN SCIENCE, 
 
 On close observation, it is found that there are many 
 Stars, called the Periodic Stars, which change their lustre 
 from time to time, becoming brighter by degrees, till 
 having attained their greatest brilliancy, they again de- 
 cline gradually, and, at last, even disappear. After a 
 while, they appear again, and go through the same 
 changes. One, for instance, the Star Omicron, in the neck 
 of the Whale, shines like a large Star of the 2nd class for 
 14 days, then decreases, and after three months disappears 
 for five months, when it reappears, and increases for three 
 months, till it attains again its greatest splendour, having 
 a period of about 332 days. The Star called Algol, in the 
 head of Medusa in the constellation of Perseus, appears as 
 a Star of the 2nd class for 62 hours, then, decreases for 
 3J hours to the ith class, and then increases again to 3J 
 hours to the second class, as at first, and so on con- 
 tinually. It is thought that some dark body must revolve 
 around such a Star, as a Planet. It must be a very large 
 body, as large, for instance, as our Sun, to hide so much 
 of the light ; but it need not be a massive body. 
 
 149. Other Stars, called Temporary Stars, are such as 
 have suddenly appeared, shone for a time with great 
 splendour, perhaps, and then disappeared, as it seems, for 
 ever. One such Star was observed B.C. 125, and it was 
 the sight of this which moved the Greek astronomer, 
 Hipparchus, to make the first catalogue of the Stars. 
 Another was seen A.D. 389, and shone for three weeks as 
 brilliant as Venus. In 1572, the great Danish astronomer, 
 Tycho Brahe, returning to his home on the evening of 
 Nov. 11, found a crowd of peasants gazing at a Star, 
 which he was sure did not exist half-an-hour before. It 
 went on, increasing in splendour for some weeks, till it 
 exceeded Jupiter at his brightest, and was seen at midday. 
 Then it gradually diminished, and disappeared in March, 
 
FIEST LESSONS IN SCIENCE. 185 
 
 1574, sixteen months after its first appearance. Other 
 Stars are certainly missing, which were once observed and 
 marked down in ancient lists. 
 
 150. There are about 6000 Stars, known as Double Stars, 
 which seem to the naked eye to be single, but, when 
 viewed by the telescope, are seen to consist of two Stars, 
 so close together that they appear as one. Some of these, 
 no doubt, only seem to be close together, when in point of 
 fact one of them may be lying immensely beyond the 
 other, though seen in the same line with it. But this is 
 not the case, generally with these Stars, as astronomers 
 are able to conclude for certain reasons. There seems to 
 be some close connection between the two Stars in most of 
 these cases, as if there were two Suns, having special re- 
 lations to each other. Frequently they are colouredj 
 and the colour of one of them depends on that of the 
 other, according to a well-known rule of the science of 
 Optics, which teaches about Light. Thus, one may 
 be bright red, or orange, and then the other will be blue, 
 or green. Some are of a blood-red colour : but no Star 
 is blue or green without a companion. Some of these 
 Stars also are triple, some quadruple, and one shows even 
 six Stars, four large and two very small. Yet when we 
 speak of their being close together, we must not forget 
 what that means in the case of Stars so distant from us. 
 If the angle between them is seen to be 1" only, yet that, 
 we know, implies a real distance of 20 billions of miles, 
 which it would take light 3^ years to travel over. With 
 many of these double Stars, the angle is less than 1" ; but 
 with others it is larger, from 1" up to 32". 
 
 151. But among them, there are many called Binary 
 Stars, which actually revolve about each other under the 
 Law of Gravitation, which thus is seen to extend through- 
 out the Universe, as far as we know it. The orbits and pe- 
 
186 FIEST LESSONS IN SCIENCE. 
 
 riods of several of these have been calculated. And among 
 them is Alpha Centauri, the nearest of the Fixed Stars, 
 which consists of two Suns, the mean angle between them 
 being 15J", so that their mean distance from each other is 
 310 billions of miles, and light would take about 50 years 
 to travel from one to the other. And yet they go round, 
 in elliptic orbits of very great eccentricity, in 77 years. 
 
 152. Trom the above it appears that it is not strictly 
 true that the Fixed Stars never change their places in the 
 sky. Yet the above motions are not noticeable by the 
 naked eye. And we may still speak of them as Fixed 
 Stars, in distinction from the Planetary bodies of the 
 Solar System. And, in point of fact, besides such move- 
 ments as the above, they are found, when observed with 
 very delicate instruments, to have a very minute motion, 
 or, rather, appearance of motion, which astronomers 
 believe to arise from a real motion of our Sun, carrying 
 all his troop of Planets with him, and revolving about 
 some distant point, or, perhaps, some other Sun, like 
 himself. We have seen that the two suns of Alpha 
 Centauri are distant 310 billions of miles. If our Sun's 
 companion were at that distance from him, he would only, 
 perhaps, be seen as a starry point ; and he may be for 
 anything we know to the contrary, much farther off from 
 him than this. It has been ascertained that this annual 
 motion of the Sun is at the rate of about one 100,000th 
 of the distance of the nearest Fixed Stars from us. Hence 
 the change of appearance in the nearest Stars, which would 
 arise every year from such a motion, may be compared 
 with that which would take place in the trees of a wood a 
 mile off from a man, in consequence of his moving one 
 100,000th part of a mile, or about half-an-inch. No 
 wonder, therefore, that to all ordinary observation, the 
 Stars still appear to be Fixed Stars. 
 
PIEST LESSONS IN SCIENCE. 187 
 
 153. But the cluster to wliich our Sun belongs, and all 
 the millions of Stars of which we have been speaking, is 
 but one of a multitude of similar clusters, which are seen 
 in various parts of the sky, but not in all parts alike — 
 being wholly absent from some regions, in others rarely 
 found, and crowded in others. To the naked eye they 
 appear like Stars seen through a mist, or as nebulous 
 specks, which may be, and often are, mistaken for Comets. 
 With a powerful telescope they are seen to consist each of 
 innumerable Stars. Each one, in fact, of these little 
 nebulous specks is a distant cluster of millions of mighty 
 Suns, like that to which our Sun belongs. Some are at 
 once seen by a common telescope to be clusters of Stars, as 
 the small, but beautiful one, which surrounds the Star 
 Kappa, in the Southern Cross, whiuh contains 110 Stars, 
 eight of them coloured with tints of red, green, and blue, 
 so that it looks like a piece of rich jewellery. Some- 
 times in the middle of such a cluster may be seen a very 
 red Star, much brighter than the rest. There is one superb 
 globular cluster, near the centre of the small Magellanic 
 Cloud (of which I will speak presently), which is very 
 visible to the naked eye, and one of the finest objects of 
 the kind in the whole heavens. It consists of a spherical 
 mass of Stars of a pale rose colour, enclosed within a globe 
 of white ones. In the famous group, the Pleiades, six or 
 seven Stars only can be seen by the naked eye. But the 
 telescope shows 60 to 60 large Stars crowded together in 
 a small space, and separated from the rest of the starry 
 host. Such clusters as these are seen to consist of 
 separate Stars ; others are seen, indeed, to be Stars, but 
 only appear as patches of starry powder. Others, again, 
 require very powerful telescopes to convert them from 
 mere dim nebulae into clusters. Sir John Herschel care- 
 fully observed, with his powerful instrument, 4000 of 
 
188 FIEST LESSONS IN SCIENCE. 
 
 these nebulsB, and drew the figures of many of them ; but 
 was often unable to show that they were clusters at all* 
 However, most of these have now been resolved — loosened, 
 d.s it were — by the still stronger power of Lord Eosse's 
 telescopes, and shown to be, indeed, masses of innumerable 
 Stars. The magnificence of some of the spectacles, beheld 
 with Lord Eosse's great telescope, when turned to such 
 clusters and nebulas, is declared, by all who have witnessed 
 it, to be such as no words can express. 
 
 154. These beds of Stars have often very curious forms. 
 Some are circular, some almost linear, which are evidently 
 very long ovals, some ring-shaped, or annular, others spiral, 
 that is curled about a centre. Many of the circular 
 nebul» are of an exactly round figure, and " convey the 
 idea," says Sir John Herschel, " of a globular space filled 
 with Stars, which constitute a family or society apart 
 from themselves, subject only to its own laws." And we 
 cannot doubt that every one of the Stars which make up 
 such a cluster is a Sun like ours, and separated from its 
 brethren of the same cluster by vast distances, such as 
 separate our Sun from the Fixed Stars, his brethren. 
 About twenty-five of these nebul® have been noted, 
 which show disks like Planets. One of these is in the 
 , Southern Cross, and is of a fine full blue colour, verging 
 upon green. Others are sky-blue. 
 
 And there are double nebulae, and, possibly, binary 
 nebulae, like double and binary Stars, having evidently 
 special relations to each other. Thus system is heaped 
 upon system, till we stand lost in adoration of the evidence 
 they afford of infinite power and unfathomable design. 
 
 155. Besides those which Sir John Herschel has de- 
 scribed, there are thousands more, which have yet to be 
 registered by other observers, and more powerful instru- 
 ments, like Lord Eosse's. Every fresh improvement in 
 
FIRST LESSONS IN SCIENCE. " 189 
 
 the telescope brings multitudes of fresh wonders into 
 view, whicli had never before been seen. 
 
 There are two nebulous masses of light, conspicuous to 
 the naked eye in the Southern Hemisphere, called the 
 Magellanic Clouds, from the name, Magellan, of the 
 ancient navigator, who first went round the world, and 
 first saw these extraordinary clouds. They are roundish 
 in shape, near one another, both large objects, but one 
 larger than the other ; and they look not unlike portions 
 of the Milky "Way, The larger can be seen in strong 
 moonlight, but not the other. When viewed through 
 powerful telescopes, they are found to be of astonishing 
 perplexity. The general ground of each consists of large 
 tracts and patches of nebulous matter, that cannot be 
 resolved, mixed up with separate Stars, and clustering 
 groups of Stars. But spread over this general ground, as 
 it were, are nebulse in abundance, of all shapes and sizes, 
 globular clusters, and nebulous objects, which are seen no- 
 where else in the sky. Within the larger cloud, there 
 have been counted 278 nebulas and clusters, besides 50 
 or 60 more upon its borders ; and this far exceeds the 
 average of any other part of the sky, even of those parts 
 most crowded with nebulse. 
 
 156. And each of these is a cluster of glorious orbs, 
 millions upon millions, each, like our own Sun, shining 
 with its own light, and, probably, giving light and heat to 
 its own troop of attendant Planets. We must speak here 
 with reverence and bated breath, bowing our hearts before 
 the all-adorable Majesty of the Great and Blessed God. 
 Are these inhabited worlds? We know not yet; nor, 
 perhaps, will it ever be given to man to know in this life. 
 But we cannot suppose that they were all made to give 
 Tis light by night, when one Moon would give more light 
 than all the Stars, or only to exhibit a grand and glorious 
 
190 FIEST LESSONS IN SCIENCE. 
 
 sight, when so few eyes can even see the vast multitudes 
 of the starry hosts, and few can know even that which you 
 will now know, of the awful wonders they reveal to us. 
 Our happy privilege is to be able to look up, and say 
 " our Father," to Him who made this mighty Universe, 
 taking with us the words, which Christ Himself has 
 taught us, and believing that He, who has given us the 
 powers, which we have, for seeing and feeling the Great- 
 ness and Goodness of His Works, has meant us thus to use 
 them, and will bless us of a truth, while we devoutly " pon- 
 der these things," and seek to "understand the loving- 
 kindness of the Lord." God grant us so to live on Earth, 
 that we may be counted worthy to stand before Him at 
 the last, and see the Glory of His Kingdom for ever and 
 ever ! Meanwhile, from each inmost recess of the great 
 temple of the Universe, into which we have been permitted 
 to gaze, we may hear, as it were, the same solemn utter- 
 ance, " Stand in awe, and sin not : commune with your 
 own hearts, and in your chamber, and be still. Offer the 
 sacrifice of righteousness, and put your trust in the Lord." 
 157. In this book I have written chiefly about the 
 Sun, and Moon, and Stars. Let me now add a few more 
 words about the wonders which Geology reveals to us. 
 Standing on the very threshold of that science, a student 
 must feel himself almost overwhelmed, at first, with the 
 awful sense of the enormous lengths of time which have 
 passed, since first the world in which we live was called 
 into being. He will obtain from it such an idea of eternity, 
 as he has never had before. He looks in, as it were, into 
 some dim vaulted chamber, and sees arch after arch reach- 
 ing away before him, till he can see no farther. He 
 follows, trembling with emotion and dread, through the 
 still, solemn, halls ; and, when he has at length stepped 
 on into the gloom, far from the, light of day and the 
 
PIKST LESSONS IN SCIENCE. 191 
 
 converse of his kind, he sees the interminable range of 
 arched pillars stretched out as before, age after age, into 
 the infinite Past. Snoh is the feeling, with which any 
 thoughtful person must read the records of the Earth's 
 past history, written upon the rocks. You have been told 
 something about this already, and, I hope, will learn more 
 about it from another little book, which I am about to 
 write for you. But one simple fact I will set before you 
 now. The coal-beds of Nova Scotia, including both the 
 seams of coal and the beds of clay and sand deposited 
 between them, are known to be three miles in thickness. 
 The coal itself is mere vegetable mould, formed by the 
 dropping of leaves, and the decay of plants, through a 
 long lapse of years, in the thick luxuriant forests, which 
 grew of old, as they grow now near the mouth of some 
 mighty river. And the layers of sand and clay were 
 brought down by the stream in its times of flood. It is 
 certain that such coal-beds as these could not have been 
 formed in less than 350,000 years. And yet this, we 
 know, is but one of many other such ages, which must 
 have passed, since first God gave the word, that this Earth 
 should be. 
 
 158. And Man has been living for a few only of these 
 years at most upon the Earth ! We know this certainly, 
 because, though we find traces innumerable of other living 
 creatures, of beasts and birds and fishes and insects, buried 
 up in the older strata of the Earth's crust, we find none 
 whatever of man, except in those of the most recent date 
 — no bones of his skeleton, no signs of his art. "We cannot 
 surely say that the Earth was made only for man. When 
 we think of the ages full of glory and beauty and life, 
 which have passed away before man was, and of the very 
 small portion of the Earth's thin crust, which he can even 
 see and examine, much less turn to his uses, we cannot 
 
192 FIRST LESSONS IN SCIENCE. 
 
 presume to think tliat the whole huge earth was made 
 only for man. As well might we say that the Sun was 
 made only to give him warmth by day, and the Moon and 
 the Stars to give him light by night. Yet, though not 
 made only for Man, these things have been made, in the 
 Great Creator's scheme, with express and most gracious 
 reference to Man. The Sun that, hundreds of thousands 
 of years ago, gave light and heat, under which the forest 
 grew in tbose primeval swamps, where the coal-beds of 
 Nova Scotia were formed, must have shone with some 
 express reference to such a being as man, who should be 
 able to make use of such stores as these of hidden treasure, 
 to draw them out of the depths in which they have so 
 long been buried, to turn them to his' uses, to contrive the 
 mighty engines that minister so vastly to the comforts of 
 his daily life, and supply the means of intercourse and 
 communion with his fellows. "Who but a creature like 
 Man, could have turned to account the coal, and the lime, 
 and the slate, and the building stones of various kinds-^ 
 the iron, copper, tin, and lead, and the multitude of other 
 substances, mineral and vegetable, which the care of the 
 Creator has provided ? How plainly does the simple fact 
 that these things are, and that man alone is capable of 
 using them, prove to the reasoning mind that, whatever 
 may be the case hereafter, whatever may become of the 
 Earth, whatever creature may be placed upon it, yet. man 
 was intended from the first to inhabit this world in his ap- 
 pointed time ; and all the ages that have passed, whatever 
 else they have done, have done this also, to fit the Earth 
 to be the home for a time, and the working-place of man. 
 159. Ah, yes ! man's working-place — a place where we 
 must work out that which accords with the spiritual nature 
 given us. We are sure that in the sight of Him, who is a 
 Spirit, spiritual beings, such as we are, must have a value 
 
FIRST LESSONS IN SCIENCE. 193 
 
 very different from that of creatures, who have merely- 
 bodily life, and those lower instincts, which distinguish the 
 brute beast from the plant. They cannot know the right 
 from the wrong, the good from the evil. "We have the Law 
 of God written within our hearts by the finger of our Maker. 
 We have the gracious teachings of His Spirit, the whisper- 
 ings of His Love, the sense of His Displeasure. We have 
 within us the faint reflexions of His glorious excellencies. 
 We know His perfect Truth, and Purity, and Goodness, by 
 that very power which He has given us, to take delight 
 in Truth, and Purity, and Goodness — ay, to love and 
 honor and glorify it in our very heart of hearts, even 
 when we are giving way to some vile temptation, and 
 consent to do what we know to be evil. And there is 
 that within us which tells us, as plainly as the Bible tells 
 us, that. the " wages of sin is death," that " he who soweth 
 to the flesh shall of the flesh reap corruption." And there 
 is something too which tells us that to do the will of God 
 ia life, such life as spirits need and long for — the life 
 Eternal, which comes from knowing Him more truly, from 
 whom all Light and Life are flowing. 
 
 160. If we had not the Bible to teach us — the utterances 
 of men's hearts in other days, breathed into by the Spirit 
 of God, and answering to that, which we feel within our- 
 selves, breathed by the One and selfsame Spirit — yet the 
 contemplation of the works of God shows us an Order also 
 in His Universe — a steady, constant, sequence of cause and 
 effect — the permanence of fixed laws, from the very first 
 age of the world's existence until now. Those, who first 
 begin to study the formation of the Earth's Crust, may be 
 led, as many have been, to imagine that by some irregular 
 wild, convulsive efforts, unlike any which we now see in 
 Nature, the rocks were made, and the mountains raised, 
 and the valleys sunk. They may fancy that such immense 
 
 o 
 
194 FIRST LESSONS IN SCIENCfE. 
 
 results as these could only have been brought about by a 
 succession of violent earthquakes, by mighty volcanic 
 action, such as might speak, indeed, of Power and Wisdom, 
 of a Will working all things to an end, but would leave 
 upon the mind a painful, bewildering, sense of disorder, 
 confusion, insecurity. But true Science teaches us other- 
 wise. It tells us that there is, indeed, a Living Euler of 
 the Universe, who has made His actual Presence felt, and 
 shown forth His Might and Wisdom, from time to time, in 
 fresh acts of creative power, calling into existence, as He 
 saw good, new races of living creatures, differing in size, 
 and form and nature, in wonderful variety, to fill up their 
 part in His stupendous whole. But it tells us also that 
 these, when created, fall at once under fixed Laws. It 
 tells us that even the Volcano and the Earthquake, the 
 Equinoctial Gale and the Thunderstorm, are all under 
 Law to God, are all governed by laws, such as we our- 
 selves can turn to account for a thousand daily uses, when 
 we bind the Giant Steam to do our work by land or by 
 sea, and bid the Lightning carry our messages. It teaches 
 us also that far greater results than these, which have 
 been wrought by the sudden action of fire and flood, have 
 been produced by slow, long-continued action of God's 
 laws, ceaselessly working with unwavering, unfailing 
 certainty. In one word, it makes us sure that all things 
 are ruled by Law and Order under the Government of 
 God, in the natural world ; and this tells us that the same 
 also is true in the moral world. We are made to feel that, 
 if we break God's Order, or teach others to break it, by' 
 acts of sin and fleshly self-indulgence, we shall surely 
 reap the fruit of our doings — that the results of our actions, 
 whether good or evil, are sure and certain, each according 
 to its kind, whether completed by some sudden stroke at 
 once, or long delayed, to be brought about, after a greater 
 
FIEST LESSONS IN SCIENCE. 195 
 
 lapse of time, by the same Eternal Laws. " Some men's 
 sins are open beforehand, leading the way to judgment ; 
 and others they follow after. Likewise also the good 
 deeds of some are manifest beforehand ; and they which 
 are otherwise cannot be hid." This thought makes ns 
 feel safe and happy under the Government of God. It 
 would be a miserable world to live in, if we were not sure 
 of this, that things do not go at random, by caprice and 
 arbitrary choice under His Government, but by fixed, 
 unerring, immutable Laws, the Laws of Kighteousness 
 and Truth, administered, not by mere Sovereign Authority, 
 but by Fatherly Love. 
 
 LONDON: PRINTED BY WILLIAM CLOWES AND EONS, LIUITED, 
 blAMFOItO aXSEET AND CHAKING CKOSS,