S5 Cornell University Library QK 495.S5H94 The secret of the big trees. Yosemite, Se 3 1924 001 688 591 THE SECRET OF THE BIG TREES YOSEMITE, SEQUOIA AND GENERAL GRANT NATIONAL PARKS DEPARTMENT OF THE iKTERIOR i9I3 ASHINGTON : GOVERNMENT PRINTING OFFICE I 19'3 378783 This publication may ])e purchased from the Superintendent of Documents, Government Printing Office, Washington, D. C, for 5 cents. THE SECRET OF THE BIG TREES By ELLSwiiRTir Hi-ntingtox. Yale I'liiversily, .\e\v Haven, C(Jini. In the days of the Prophet Elijah sore famine afflicted the hind of Palestine. Xo rain fell, the brooks ran dry. and dire distress pre- vailed. '• Go through the land,"' said King Ahab to the Prophet Oliadiah, "unto all the fountains of water and inito all the brooks; peradventure we may find grass and save the horses and mules alive, that we lose not all the beasts." When Obadiah went forth in search of forage he fell in with his chief. Elijah, and brought him to Ahab. who greeted him as the troubler of Israel. Then Elijah prayed for rain, according to the Bible story, and tlie famine was stayed. From this famine in Palestine, some 870 years before Christ, to the forests of the Sierra Nevadas. in the year of grace 1911, is a far cry. The idea of investigating an episode of ancient Asiatic history in the motmtains of California seems at first sight (]uixotic. Yet for the purpose of facilitating stich an investigation the Carnegie Institution of Washington furnished funds, and Yale Eni\ersity ga\'e the author leave of absence from college duties. The men in charge of both institutions I'ealize that the possiltilities of any line of research l^ear no relation whatever to its immediate practical results, or even to it-, apparent reasonableness in the minds of the tmthinking. The final otitcome of any piece of scientific work may not be apparent for gen- erations, but that does not make the first steps less important. Already, however, our results ]iossess a positi\'e valtie. The}' demon- strate anew that this world of ours, with all its manifold activities, is so small, and so botmd part to part, that nearly :^>.000 years of time and thrice 3,000 miles of space can not conceal its unity. The connecting link between the past and the present, between the ancient East and the modern West, is found in the big trees of Cali- fornia, the huge species known as Scqiioi(( wiishiiuitoiiionii. Every- one has heard of this tree's vast size and great age. The trunk of a ^ This article appeared in Hie .Tiily, 1012, minilier of Hai'iier's ;\Ia,^'.-izine. and is reiirinted here in a revised form with tlie addition of pliotogr.iphs of some of the big trees in the naticmal y)arks. The Held work was necess.arily carried en in areas outside the parks, as uo tiuilii'r is ent wilhin the r<'ser\ations. — iMlitcr. 4 THE SECRET OF THE BIG TEEES. ■,ve]l-gTown si^ecimeii has a dianietei- of liO or 30 feet, wliich is equal to the width of an ordinary honse. Snch a tree often towers '250 or 300 feet, or six times as higli as a large elm. and within .")0 feet of the top the trunk is still 10 or 12 feet in thickness. Three thousand fence posts, sufficient to support a wire fence around 8,000 or 9.000 acres, have been made from one of these giants, and that was only the first step toward using its huge carcass. .Six hundred and fifty thousand shingles, enough to cover the roofs of 70 or SO houses, formed the second item of its product. Finally there still remained hinidreds of cords of firewood which no one could use because of the prohibitive expense of hauling the wood out of the momitains. The upper third of the trunk and all the branches lie on the ground where they fell, not \isil)ly rotting, for the wood is wonderfully enduring, but simply waiting till some foolish camper shall light a devastating fire. Huge as the sequoias are. their size is scarcely so wonderful as their age. A tree that has lived ."")00 years is still in its early youth: one that has rounded out 1,000 summers and winters is only in full maturity: and old age. the three score years and ten of the sequoias, does not come for 17 or IS centuries. Plow old the oldest trees may be is not yet certain, but I have counted the rings of 79 that were over 2,000 years of age, of 3 that were over 3.000, and of 1 that was 3,ir)0. In the days of the Trojan "War and of the exodus of the Helirews from EgV'pt this oldest tree was a sturdy sapling, with stiff, i:)rickly foliage like that of a cedar, bnt far more compressed. It was doubtless a graceful, sharply conical tree, 20 or 30 feet high, with dense, horizontal Ijranches. the lower ones of which swept the ground. Like the young trees of to-day, the ancient sequoia and the clump of trees of similar age which grew close to it must have been a charming adornment of the landscape. By the time of Mara- thon the trees had lost the hard, sharp lines of youth, and were thoroughly mature. The lower branches had disappeared, up to a heiglit of 100 feet or more: the giant trunks were disclosed as bare, reddish columns covered with soft Ijiirk ('> inches or a foot in thick- ness ; the Tipper liranches had acquired a slightly drooping aspect ; and the spiny foliage, far removed from the ground, had assumed a grace- ful, rounded appearance. Then for centuries, through the days of Eonie. the Dark Ages, and all the period of the growth of European civilization, the ancient giants preserved the same appearance, strong and solid. l:iut with a strangely attractive, approachaljle quality. After one has lived for weeks at the foot of such trees, he comes to feel that they are friends in a sense more intimate than is the case with most trees. They seem to have the mellow, kindly qnality of old age, and its rich knowledge of the past stored carefullj' away for any who know how to use it. Often in the search for scientific information in remote parts of the world one comes to some primitive THE SECEET OF THE BIG TliEES. ;) village and inquiie.s "wlit'ther there are not smue old men (if loni;' experience who can tell the story of the jnist. So it is with treo: like old men, they cherish the memory of lumdreds of interesting events, and all that is needed is an interpreter. During- the summers of 1011 and l'.)l'_! the natural course of the writer's study of the climate of the past led him to attempt to learn IIARIFOSA laiOVK, YOSKMITE NATIONAL I'AI:K. I'liotugrapli by I'iUslniry I'irturi' t'n. Tlie JIariposa Grove is situated in tlie soiitlieni jioi-tioii of the Yoseiiiite Xatioiinl Park, :;.". miles from Yoseniite Valley. Tliere are two other .uroves of hi;,' ti-ecs in the Yoseniite National Pai'l; — the TiioUinme (irove of lid trees IT miles iiiirrh«'est of Y'osemite \'alley and the Merced (irove of 4(1 trees '.I miles north- west 4 feet in cirriinit'ercncc :iu(l 2(i tV'ci in dinnnr'ti'V at a imint ]<> tVft alinvt the ^'I'dnnil. » THE SECRET OF THE BIG TEEES. has not proceeded regularly, howexer, ))iit in a pulsatory fashifin. It seems to have been interrupted by centuries of exceptional aridity on the one hand and of exceptional moisture on the other. When these pulsations of climate are compared with the course of history a remarkable agreement is noticed. Among a mass of minor details this apparent relationship may be concealed, but the broad move- ments of races, the rise and fall of civilization, seem to show a de- gree of agreement with climatic changes so great that it scarcel_v seems possible to avoid the conclusion that the two are intimately related. Unfavoral^le conditions of climate, such as a change toward aridity in regions already none too well supplied witli water, have apparently led to famines, epidemics, economic distress, the decline of trade, misgovernment, migrations, wars, and stagnation ; while fa\-orable changes ha^e fostered exactly opposite conditions. This theory strikes so profoundly at the roots of all historical in- terpretation and is of such fundamental importance in its bearing on the future of nations and of the human race as a whole that it demands most careful testing. The first step in carrying on the necessary tests is obvioush' to determine the exact degree of accuracy of our conclusions as to the dates and nature of climatic changes. Only when that has been done are we prepared to proceed to a fuller investigation of the relation of the changes to historic events. After some years had been spent in a studj- of this great problem from various standpoints in Asia, the logical thing seemed to be to take up the same lines of work in some other continent and see how far the two agreed. Fortunately T was invited by Dr. D. T. Mac- Dougal to cooperate with the Department of Botanical Eesearch of the Carnegie Institution of Washington in a study of the climate of rhe southwestern part of the United States. In general the phe- nomena of ancient ruins, old strands of inclosed salt lakes, the gravel terraces of rivers, and the distribution and agriculture of the prehis- toric population seemed to indicate that the climatic history of Amer- ica has l:)een the same as that of Asia. The results, however, were unsatisfactory in two respects. In the first place, previous to the time of Columbus we knov\' almost nothing about the dates of events in America, and hence it is impossible to know whether the apparent climatic fluctuations of America agree in time with those of Asia. In the second place, a theory is a dangerous thing. Strive as he will, the author is apt to be partial to it and to interpret all that he sees in sucli a way as to fit his preconceived ideas. During my work in Ari- 2;ona, Xew Mexico, and old ^Mexico I knew that when its results were announced critics would say, '' That is all very interesting, but not convincing. You went out West expecting to find evidences of pulsatory changes of climate during historic times, and, of course, you found them. We will wait a while before we believe j^ou." THE Sl'.CKET Ol'" THE Jild 'IHEES. WAWOXA TREE, MAKIPOSA (;[10\E, YCISEMITE NATIONAL I'AKK. Photograpti liy Pills). nry Picture Co. Hei.slil", 227 fwt ; iliaiiietei-, 20 feet tliroui;li the o|ieuins: Iti feet nlieve the gi-dmuf the (lianieter is 1!) fi-et niul the circuiufei-eiire is (id feet, 'fhe mnd was cut thi-dugh this tree in ISSO. SI 701°—] 3 2 10 THE SECRET OF THE BI( i TREES. IMunift.stly it was ntces.-ary to (Ie\ise .some new liuc (if researeli which shouki not only furnish dates, but shoukl prove positively the existence or nonexistence of changes of climate, and should do it in such a way that the investigator's private opinions, his personal equation, so to speak, should not be able to affect his results. The necessary method was most opportunelj^ suggested by an article pulilished in the ^lonthly "Weather Eeview in 1909 Ijy Prof. A. E. Douglass, of the Universitj' of Arizona. In regions having a strongly marked difference between summer and winter it is well known that trees habitually lav on a ring of wood each year. The CROSS SICCTION OF A SrCQUOrA SIIOWIXG THE f;ROWTH RINGS. wood that grows in the earlier part of the season is formed rapidly ;ind is soft in texture, while that which grows later is formed slowly II ud is correspondingly hard. Hence each annual ring consists of a layer of soft, pulpy wood surrounded l^y a thinner laver of harder wood which is generally of a darker color. Except under rare con- ditions only one ring is formed each year, and where there are two rings by reason of a doitble period of growth, due to a drought in IMay or June followed by wet weather, it is nsually easy to detect tlie fact. In the drier parts of the temperate zone, especially in regions like Arizona and California, Ijy far the most important factcu- in determining the amcaint of growth is the rainfall. Prof. Douglass measured some I'O trees averaging about .300 years old. He found that their rate of growth during the period since records of rainfall THE SECKET (IE THE Jil( I 'I EEES. 11 lia\e Iji't'ii lu'])! Aiirics in iKinnciiy wiUi Ihc aiiiDiiiit of jirecipihilidn. Other im'estiiiators lia\e since done siniilar ^\(irk elsewlicre. ami it is now estalilislied that in regions with cohl Avijiters and drv siiirnneiv^ the thidvness of the ajinnal hiyers (if prowtli a'i\"es an a|i]ii'(ixiiiiale measure of llie amount of rain and snow. Obviously the best trees upon whieli in te~.t the theory of elimatie changes are the big trees of California. They grow at an altitude of 0.000 or 7.0(10 feet on the western slope of the Sierra Nevada-. Abundant snow falls in winter and there is a fair amount t of .June, but the re-t (if the warm -eason until the end of Se]itemlier is dry. Hence the (•onditidns ai'e liiddv 12 THE SECRET OF THE BIG TREES. favorable to the formation of distinct, easily-measured rings. The size of the trees makes the rings fairly thick, and hence easy to see. The only difficulty is that the number of trees which have been cnt is small. The region where they grow is relatively inaccessible, the huge trunks are very difficult to handle, and the wood is so soft that its uses are limited to a few purposes for which great durability is I'cqnired. TTence several years may pass without the cutting of more than a few scattering trees. The resistance of the wood to decay is so extraordinary, however, that stumps 30 years old are almost as fresh as when cut, and their rings can easily be counted. A> climatic records they are as useful as trees that were cut the present yeai'. if only one can ascertain the date when they were felled. Toward the end of ^May. 1011, I left the train at Sanger, near Fresno, in the great inner valley of California, and with two assist- ants drove up into the mountains through the fieneral Grant National Park to a tracl belonging to the Hume-Bennett Lumlier Co. There we camped for two weeks, and then went to a similar region, some (JO miles farther south on the Tulare Tliver, east of Portersville. Few parts of the world are more delightful than the Sierras in the early summer. In the course of our work we often tramped through val- leys filled with the straight, graceful cones of young sequoias over- topjied by the great columns of their sires. Little lirooks or rushing streams full of waterfalls flowed in every de]iression, and a drink could be had whenever one wished. On the sides of the valleys, wliere the soil is thin and dry, no young sequoias could be seen, al- though there were fretjiieiit old ones, a fact which suggests that conditions are now drier than in the yiast. Other trees, less exacting in their demands for water, abound in both their young and old stages, and one climbs upward through an array of feathery pines, Ln'oad-leaved cedars with red bark, and gentle firs so slender that they seem like veritable needles when compared with the stout sequoias. We tramped each day to our chosen stumps, sometimes following old chutes made by the lumlxn'men to guide the logs down to the valleys, and sometimes struggling through the bushes, or wandering among uncut portions of the primeval forests. Often there was frost on the ground during the first Aveek or two, and the last rains of the spring made the ground oozy, while the flat tops of the stumps smoked in the summer sun as soon as the clouds disappeared. Our method of work was simple. As soon as we reached a place where .sequoias had been cut. we l)egan prospecting for large stumps. The method of cutting the trees facilitated our work bv furnishing a smooth sawed surface. r>efore the lumbermen attack one of the giants they build a ])latform about it feet or more above the ground and high enough to be clear of the flaring Ijase of the trunk. On this TIIIC Sl'X'liET (II' 'IIIE j;i(i IIIICJ^S. 13 t«'o nifii stjiml :iii(l cliiip (Hil hii^-c cliiiis. suiiicl inics w fool niiJ n li:ill' Ini]^;-. As tin' cilltiliL'; [irdcccds il i;tc;!1 iiolcli is foriiicd. Il;il ini tlic l)ottnni and liiii'li eiKHieh sn lliat Uic iiicii acdialh- -(and within it. In this way tln'v cho];) 10 feet iiKirc or less iiidi the tree, until l!n'\' aiijiroach the center. Then they take a liand saw l.^i or -JO feet huii;- and "•() around to the other side. For the next few (hivs (hey ]inll the great saw hack and fVuHi. soaking it liberally in oi'ease to niakr It slip easily, and driving wedges in behind it in order to |ircvcnt the weight of the (ree from res(ing on (he saw. Finally, when the ti-ee is almost cut through, more wedging is (hme, and the lielpless trnnk topples f)ver with a thnd and a stnpendons erackinii' of lii'anches 14 THE SECRET OF THE BIG TREES. timt can be heard a mile. The sawn surface e.xposes the rings of lirinvtli so tliat all one has to do is to measure them, provided the cutting has taken place recently. In the case of older stumps we sometimes were oljliged to scrape the surface to get rid of the pitchy sap which had accumulated on it. In other cases, especially where the stumps had been burned, we had to chisel groo^•es or take a whisk- broom and sweep olf an accumulation of needles and dirt. When all was ready, two of us lay down on our stomachs on the top of the stump, or it might be on two stumps standing close together, while the third sought the shade, or the snn. or a shelter from the rain, as the weather jviiglit dictate. The two who were on tlie stump were eijuipped with penknife, ruler, and hand lens. The ruler was placed on the flat surface of the stimip with its zero at the edge r.f the outer ring. Then we counted (itf the rings in groups of 10. read the ruler and called oti' the number to the one who sat under shelter with notelidok and pencil. Had the lumbermen seen us we should have ai)iieai'ed like crazy creatures as we lay liy the hour in the ^un and rain calling nut " forty-tw(i," and being answered by the recorder, •■forty-two": "■ sixty-fy tlie danger that the results of our two measurements might not agree. The chief interest therefore lay in seeing how nearly the same number of rings would l)e counted on different radii. If we were at work on dif- ferent trees the rivalry was as to whose tree would turn out oldest; for. like the rest of mankind, we had a feeling of personal merit if tlie thing with which we l_)y pure cdiance were concerned happened to turn out better than that of our neighbor. One of our chief difficulties lay in the fact that in Ijad seasons one side of a tree often fails to lay on any wood, especially in cases where a clump c;f trees grow together in the sequoias" usual habit, and the inner portions do not have a fair chance. Often we found a dif- ference of 20 or 30 years in radii at rigbt angles to one another; and in one extreme case, one side of a tree :>.000 years old was ^lOO years older than tlie other, according to our count. All these things neces- sitated constant care in order that our results might be correct. Another trial lay in the fact that in spite of the extraordinary dura- bility of the v^'ood, a certain number of decayed places are found, TIIK SEL'IMCT Oh' 'I'JIE ];1(; ■J'UI'.I^S. ], eirpeciiilly at the centers (if the older ti'ees. exactly the ]ilai-e^ which (iiie most desires to see preserxed. E\'en these decayed places, how- I'wr. adh frog.s, which slowly retreated if we Itecanie in(iuisiti\-e and poked them. At other times, in drier ])laces. lizards of a smooth, iin- 16 THE SECFIET OF THE BI( i 'JREES. lileasunt complexion of brownish gray wriggled hastilj' into cavities in the rotten wood. Once I pnlled (iff a hu'ge decayed shilj from the side (if a fitnm]i. and started baclv in snrprise wlien two creatures GENERAL GRANT TREE, GENERAL GRANT NATIONAL PARK. Ileii^lit, 2c,4 feet; di.inietev, 35 feet. The (^itnerul (inint (irove, iu the park of tlie same name, liiis an urea of 2:.!."j ata-es aiKt contaiiis 100 trees exeeeJinp: 1(1 feet iu diameter. Avitli ^■e^owishdJr()wn bodies and bhtck wings fiew ont. I was about to look for a bird's nest when one of my companions called out " Bats.'' THE SKCRliT (IF THE BI(_1 TREES. 17 The frogs, lizai'ds. and bats did not trouble lis, and, fortunately, we were free from mosquitoes. There was one creature, howexer, which sometimes seriously interfered with our work'. As we lay on lair stomachs, our left lists resting on the black surface of a stunip to jirop oiu' unshaven chins, and our right hands ra[)idly touching ring after ring with a penknife as we counted our decades — as we lay thu.s. with eyes closelv focused at a distance of about s inches, frightful fdrins came rushing into the field of vision. They were black and horny, with powerful nippers on their heads, and with white hairs on their 18 THE SECRET OF THE BIG TREES. iilxlomens, giving them a niok^y look. Tliev seemed nearl)' a,s large as iniee. and their speed of movement was jiositivel^' alarming. With open nippers they mshed at our rulers and knives and tried tliem to see if they were edible. Sometimes they even nippd our hands, and more than once one of us uttered a sharp exclamation and jumped so as to tlirow knife and rider to the winds and cause the waste of 10 or 1.^) minutes in finding the place again. "When we l)rushed the crea- tures away and looked at them from the noruial distance they proved to be nothing but large black ants, about half an inch long. [More i^ertinacious insects I never saw. Again and again T l)rushed an ant away to a distance of (5 or 8 feet, and watched that same ant turn the mouient it aliglited and ru.sh back to the attack, and it did this not once but five or six times. During the 12 weeks that we were in the mountains in the two seasons of 1011 and 1012 we succeeded in measuring over 450 trees, 70 of whicli were 2,000 or more years of age. The others were of A arious ages down to 2.50 j'ears, for we measured a considerable num- lier of relatively young trees for purposes of comparison. The proc- ess of constructing tlie climatic curve from the data thus obtained is less simple than might at first appear. The obvious method is to ascertain the average growth of all the trees for each decade, from the earliest times to the present, and then to draw a curve showing Ijow the rate has varied. The high places on such a curve will indi- cate times of comparative moisture, while the low ]ilaces will indicate aridity. This method is too simple, Iiowe-\-er, for it takes no account of the fact that all trees grow faster in youth than in old age. Each species has its own characteristic curve fif growth, as it is called. l"or example, during the first 10 years of its life the average Sequoia iri/s/i/'iii/to)i/'aiia grows aljout an inch in radius, that is. it reaches a diameter of 2 inches; at the age of 200 years the average tree adds about nine-tentlis of an inch to its radius each decade; at the age of •"lOO years about six-tenths of an inch; and at the age of 1.700 only three-tenths. These figures have nothing to do with the rainfall, but indicate liow fast the tree might l)e expected to grow if they were -ubject at all times to the average climatic conditions, without any A'ariations from year to year. Evidently, if we desire to institute a fair cf)mparison between the growth of a tree 200 years old and of one 1.700 years old, we mnst either nuiltiply or divide by o. Ry applying such corrections to each measurement among the lO.'i.OOO which made up the work of our two sunnners. we are aljle to eliminate the effect of differences in the ages of the trees. The process is jnirely mathematical and depends in no respect upon the individual ideas of the computer. In addition to the correction for age, there is another, whicli I have called the cor- rection for longevity. "What sort of tree is likely to have a lone life? THE SECRET OF THE Bid TKEES. K- Is it n vigorous. well-i;i'owii tii'c, the Idiid that one would pick out ns especially flonrisliing in its yoiitli'^ Not at all. Tlie tree which is hkely to live to a ripe old aex' of two or three thousand years iirows H'OIAS n.\ CIA^T II lA XAl'lllXAI. PAKK. Tlie Oi.iiit FnresI- b;is an -.wca of .".'JOO .-ici-es and contains riOn.oiiO n\'(-s. of wliicLi o.iiiio exceed 10 feet in dianietoi-. TIhtc are It otlier Lcrores in the Sequoia National V:\vk raiif^in.^ from fl> to ll.ono a.a'es in afca and containing from II tn ;;.0(Ml trees exi-eedin^' 10 feet in diameter. slowly in ils earlv days. Its aittial rate of oi'nwtli may lie only half or two-thirds as o-reat as that of the trees Avhich attain an age of ."lOO 20 THE SECfiET OF THE BIG TREES. x: >■ ./ \ ,! -^- oi- l.OUO years. Hence, in order to institute a fair comparison between the rate of growth in tlie days of Darius and now it is necessarj' to nialvC still furtlier corrections. This process, like the other, is purely mathematical. The only difficulty is tliat in order to secure high accuracy a large number of trees of all ages is necessary. It is easy to obtain plenty of young trees under 2.000 years of age. but older ones are so scarce that we have not obtained enough to render the corrections fully exact. Hence in the earlier parts of the curve, the details are less exact than could be desired, and the fluctuations are relatively too great, since they are not smoothed out by the use of a large number of trees. In the portion of the curve since about 100 B. C., however, the tluctuatidus for minor periods and also for centuries show no appre- ciable errors except such as are due to special accidents. Nevertheless there is some douljt as to whether the curve as a A\hole in its descent from early times down to the pres- ent should slope more or less than is here shown. Tlie accompanying diagram sums up the results of our work on the big trees as compared with the re- sidts of work of an entirely differ- ent kind upon the climatic fluctua- tions of Asia. Horizontal distance indicates time: the diagram begins at the left-hand end with 1300 B. C. and ends on the right with IHOO .V. I). Vertical distance indicates a greater or less amount of rainfall or more or less favorable condi- tions of plant growth. The solid line is tlie curve of the sequoias. During the periods where it is high, THE SECRET < >E THE Bill TliEES. 21 abundant nioi.sture stiiniilatcd rapid nrnAvdi; "wlicic it i^ low. j)eri<)ds of aridity lastin*; often for centuries clieelved the L;ro\vtli (if the tree,-. The other eiir^e-tlie (hit ted line, is reproduced nucha ui;ed froiu the au- GKNliilAL .SIIIRIIA^', CIAXT FnRi:sT. Si:(;iI/OIA A.MIONAI. PAUK Hei;-'lit, I'm; I\v\ : diaineter, '■'■''< feet. thor's volume on ■■Palestine and its Transforiualiou.'" It reiirescnls the state of our knowledi;e of the chauiies uf climate of we-tern and central Asia at the time when that volume was written in f'.)10. The 22 THE SECRET OF THE BK ; TKEES. e\ideiice upon -which it is Ijasyil is (if Aei'V dixerse types, and \':iries greatly in accuracy and abunihmce at different periods. For example, the low portion of the curve about 1200 B. C. is based on records of ancient famines, and upon the fact that at that time great movements of desert peoples took place in such a way as to suggest that the des- erts had Jjecome much less habitable than formerly- A few hundred years later the curve is high, because at this time not only did great prosperity prevail in regions which are now poverty stricken for lack of rainfall, but the kings of Assyria and the other countries lying iiear the Arabian Desert appear to have been able to take their armies in comparative comfort across regions where small caravans can not now 25:iss. and which even the hardy Arab raiders avoid. At a later time, 300 A. D., the curve drops low, because at this period a great tiumber of towns Avere abandoned in central Asia and in all the drier parts of the Continent; trade routes which had formerly Ijeen much frequented were absolutely given tip in favor of those where water and forage were more easily obtained; and in coun- tries like Syria stagnation seems to ha^e prevailed, as is indi- cated by the scarcity of building operations during these years. The curve dips Icjw at this point simply because evidences of aridity began to be conspicuous; but probably it dips too low, for there is as yet no means of obtaining exact data. In the seventh century A. D. evidence of the same kind as in the third causes the curve to drop still lower, but here we have additional proof of ariditv in the form of traditifins of ]irolonged famines in Arabia. ^Moreover, at about this same time the waters of the Caspian Sea and of other lakes without outlets were not replenished by rain, and hence fell to a level so low that buildings were built upon what is now the bottom of the lake. Then, at a later date, about 1000 A. D., the ruins in the desert were partially reoccupied. the old trade routes began to revive, the lakes rose higher than their present level, and prosperity ■\',as the rule in many regions which had formerly suffered from aridity. These liits of evidence, gathered here and there, have en- abled the curves to be drawn, but accuracy is as yet out of the question. At most the curves are a mere approximation, showing some of the main climatic pulsations, btit likely to be greatly modified as further investigation is made. On the whole there are indications that further knowledge of the Asiatic curve will prove that it is much more like the California curve than now appears. Yet in the main the two curves even now show a consideralile degree of agreement, and in that agreement lies the strongest evidence that both are cor- rect in principle, although they may be wrong in detail. Let us begin at the left-hand end far back at the time of the Trojan War. There, aboiu 1200 I>. C.. both cur\es drop very low, indicat- ing an epoch of sudden and severe desiccation. That particular THE SECRET OF THE BKi TREES. 23 period, historians tell us, was one of the most chaotic in all liistory. The warlike proecome extremely dry. notli- ing like so bad as it had been a few hundred years earlier during tin.' twelfth century, but there was a rather distinct falling off in the amount of rainfall as compared with the uncommonly goo. C., and a recovery reaching a hioh point about r)0 B. C. The time of Christ, the great era of universal jjeace under the sway of Kome, was apparently an epoch of favoraf)le climate, a time of abundant rain and consequent good crops in all the countries around the Mediterranean Sea and eastward in Asia, as well as in California. Next comes a long period of decline cul- minating six or seven centuries after the time of Christ. The sudden drop of the Asiatic curve about 300 A. D. is probably exagijerated. as are those from 550 to 050 A. D. and in li'OO. Nevertheless, there can be little question as to the general agreement of the two curves in showing that an epoch of extraordinary ariditv reached its climax hi the seventh or eighth century of our era, and that another period of aridity occurred in the thirteenth century. Previous td the sev- enth century the Roman world had been in tlie direst straits liecausc of the invasions of Ijarbarians. dri^'en from their liomes. it would seem, by increasing aridity and the consequent difficulty of ol^tainino- 24 THE SECKET OF THE BIG TREES. a living. Then, toward the end of tlie long period of drought, there occurred the tremendous outpouring of the Arabs, unified by Moham- luedauism. as is universally agreed, and also spurred by hunger, as we infer from a study of climate. Thus the Dark Ages reached their climax. Xo period in all history, save that which centers 1200 B. C., was more chaotic ; and that early period also ajopears to have lieen a time of greatly diminished rainfall. It is impossible here to trace further the correspondence of the two curves and their relation to history. The essential point is this: Bv means of a rigid mathematical test we have worked out the cliniatii changes of California. From ruins, lacustrine strands, traditions, famines, and many other lines of evidence we have worked out the changes in Asia. Thus by methods absolutely dissimilar we have constructed curves showing climatic fluctuations in parts of the world 10.000 miles apart. In essentials the two agree in spite of differences, in detail. It therefore seems probable not only that climatic pulsa- tions have taken place on a large scale during historic times, but that on the whole the more imjiortant changes have occurred at the same time all around the world, at least in the portion of the north tem- perate zone lying from 30^^ to 10' north of the Equator. This, m itself, does not prove that great historic clmnges have occurred in response to climatic pulsations. Itut it goes far in that direction. It introduces a new factor into that most profound and far-reaching of the problems of history — the cause of the rise and fall of nations. O