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I SECOND TREATISE 
 
 DECREASE OF WATER 
 
 SPRINGS, CREEKS, AND RIVERS, 
 
 CONTEMPORANEOUSLY WITH 
 
 AN INCREASE IN HEIGHT OF FLOODS IN CULTIVATED COUNTRIES, 
 
 SIR GUSTAV WEX, 
 
 IMPERIAL AND ROYAL MINISTERIAL COUNSELLOR AND CHIEF ENGINEER 
 OF THE IMPROVEMENT OF THE DANUBE, AT VIENNA, 
 
 WITH SIX SHEETS OF DRAWINGS 
 
 FROM THE PAPERS OF THE SOCIETY OF THE AUSTRIAN ENGINEERS 
 AND ARCHITECTS, 1879— Nos. 6-9. 
 
 TRANSLATED BY 
 
 a. WEITZEL, 
 
 Major of Engineers, Brevet Maj. Gen. 
 
 WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 
 1880. 
 
is 1 5 
 
 W53 
 
SECOND T R E A T I S E 
 
 OX THE 
 
 DECREASE OF WATER IN SPRINGS, CREEKS, AND 
 
 RIVERS. 
 
 Office of the Chief of Engineers, 
 
 United States Army, 
 Washington, D. C, July 1, 1880. 
 Sir : An interesting paper on hydraulic engineering entitled "Zweite 
 Abhandlung iiberdie Wasserabnahme in den Qnellen, Fliissen and Stro- 
 nienbeigleichzeitigerSteigeruugder Hocbwiisser in den Culturlandern " 
 (Second treatise on the decrease of water in springs, creeks, and rivers, 
 contemporaneously with an increase in beigbt of floods in cultivated 
 countries), by Sir Gustav Wex, imperial and royal ministerial counsellor 
 and chief engineer of the improvement of the Danube at Vienna, has 
 recently been translated, at my request, by Bvt. Maj. Gen. G. Weitzel, 
 United States Army. 
 
 As this paper contains information of value to the officers of the 
 Corps, I have the honor to recommend that it be printed, for the use of 
 the Engineer Department, at the Government Printing Office, and that 
 500 copies be furnished on the usual requisition. 
 Very respectfully, your obedient servant, 
 
 H. G. WRIGHT, 
 Chief of Engineers, Brig. & Bet. Maj. Gen. 
 Hon. Alexander Ramsey, 
 
 Secretary of War. 
 Approved : 
 By order of the Secretary of War. 
 
 July 6, 1880. 
 
 H. T. CROSBY, 
 
 Chief Cleric. 
 
 Vienna, October 12, 1870. 
 General : I take the liberty of transmitting to you in the accom- 
 panying-package my second treatise, entitled " On the decrease of water 
 in springs, rivers, and streams, simultaneous with the increase of floods 
 in cultivated countries," because I am convinced that such a distinguished 
 hydraulic engineer will take a lively interest in the definite solution of 
 
a hydraulic question fc which is of the highest importance to coming gen- 
 erations and future condition of cultivated countries. 
 
 At the same time you will please have the kindness to accept this 
 copy as a mark of my most eminent esteem. 
 
 Finally, I take the liberty of politely begging you to transmit for use 
 the other copy of^iny treatise which accompanies this to the esteemed 
 societies of engineers which exist in your country, with the request that 
 they may thoroughly examine my theory with regard to the decrease in 
 water supply, and illustrate it more clearly by the publication of the 
 hydraulic observations made on American rivers and streams. 
 
 With the assurance of my highest esteem, I remain your devoted 
 
 Sir GUSTAV WEX, 
 Imperial and Royal Counsellor. 
 
 Brig. Gen. A. A. Humphreys, 
 
 Chief of Engineers, Washington. 
 
INTRODUCTION 
 
 In my first treatise bearing the foregoing title, published in the papers 
 of the Society of Austrian Engineers and Architects, 1873, after observ- 
 ing gauges during many years at nine different stations on the five 
 main rivers of Central Europe, viz, the Danube, Rhine, Elba, Vistula, 
 and Oder, and also after many other observed results, I furnished the 
 proofs that the discharge has diminished considerably during the latter 
 decade, not only in the above-mentioned rivers themselves, but also in 
 their tributary rivers, creeks, and springs. 
 
 In that treatise I also thoroughly discussed the causes of this peculiar 
 hydraulic phenomenon, and finally proposed measures and precautions 
 to prevent as far as possible the further spread of this calamity, so 
 threatening to future generations. 
 
 Since the publication of that treatise, this hydraulic question thus 
 raised by me has been industriously studied in nearly all countries, 
 partly by scientific institutes and partly by individual naturalists and 
 experts, and their various opinions and views have been published. 
 
 In by far the greater number of the opinions which have thus ap- 
 peared some of these scientific institutions and authors have entirely, 
 and others only partially, agreed with my views, conclusions, and the 
 theory which I recommend, and, at the same time, have brought for- 
 ward many new illustrations and arguments to establish its correctness. 
 
 But especially, as several engineers and hydraulic experts have 
 expressed the opinion that my conclusions as to the decrease in the 
 height of water in rivers are unreliable, and that the remaining proofs 
 for the decrease in discharge are not quite unassailable, and, besides, 
 because several of these experts have even advanced the new theory 
 that the established decrease in the height of the water is not in conse- 
 quence of the decreased discharge, but rather due to changes in and 
 particularly to the deepening of the river beds, I have during six years 
 shunned neither labor nor expense in obtaining as many and reliable 
 technical hydraulic measurements and data as possible of different 
 streams, so that I might clearly ascertain whether the views previously 
 expressed by me or those of my opponents were more nearly correct. 
 
 Now that I have in the course of these uninterrupted and continued 
 collections of data and studies, and even by the latest of these, arrived 
 at the fullest conviction that the theory advanced by me relative to the 
 decrease in the discharge of springs, rivers, and streams lias been unfor- 
 tunately proven true, I feel myself impelled to publish this second 
 treatise, since 1 believe that an indisputably clear exposition of this 
 water question is not only of great importance in technical hydraulics, 
 but also in its bearing upon questions in natural science and history of 
 culture, as I have already pointed out in more detail in my first treatise. 
 But a general knowledge of the decrease in discharge of springs and 
 rivers and the resulting highly detrimental consequences for the future 
 cultivation of countries and their inhabitants is absolutely necessary, 
 
6 
 
 for then alone it can be hoped that the general governments, corpora" 
 tions, large land-owners, and individual communities will take suitable 
 precautions and measures to confine the calamity to such limits as are 
 yet feasible. 
 
 In Chapter I of this treatise I shall present, very briefly, the opinions 
 given on the question by scientific institutes first, and then those of the 
 individual naturalists and experts who agree with me ; and subsequently, 
 in Chapter II, with the latest data collected by me as a basis, will fur- 
 nish the proof that the objections made by my opponents, and the new 
 theories established by them, are either groundless or are based upon 
 incorrect premises. 
 
 CHAPTEE I. 
 
 1. The Imperial Academy of Sciences in Vienna, at my request, ap- 
 pointed from its own members a commission of five experts to give a 
 formal opinion upon my treatise, which commission, after a thorough 
 examination, in their report dated April 23, 1874, declared themselves 
 in general as agreeing with me in my proofs and conclusions, and only 
 remarked that my conjectures that the rainfall in cultivated countries 
 must now have equally decreased, as not sustained by the meteorolog- 
 ical observations made in England, Scotland, and at Paris during a 
 period of many years, and although it would be hasty to conclude from 
 this that no such changes have taken place in the interior of the continent, 
 yet the measurements of rainfall at the continental stations (which, how- 
 ever, do not reach so far back) are not favorable to such an assumption. 
 
 The Imperial Academy of Sciences at its anniversary meeting of May 
 30, 1874, accepted the above-mentioned report of its commission, and 
 resolved at the same time : 
 
 (a) To call the attention of the Imperial and Royal government to the 
 continued decrease of discharge in springs and streams, as well as to the 
 causes of the phenomenon, and at the same time to apply to the higher 
 ministries, so that the measures and precautions proposed by Wex to 
 prevent, as far as feasible, the further spread of this calamity may be 
 thoroughly considered and carried into execution by the enactment of 
 suitable laws. 
 
 (b) To send a copy of Wex's treatise to the scientific institutes of for- 
 eign countries with the request that they furnish the Imperial Academy 
 with the results of observations extending through a series of years of 
 the gauges in their rivers, and to furnish this information arranged and 
 plotted in a manner similar to that adopted in his treatise. 
 
 (c) To express, also, to the Austrian Government the desire that sta- 
 tions may be erected at suitable points on several rivers, not only to ob- 
 serve the stages, but also to measure the discharge, in order to examine 
 more closely the laws of dependence of the latter on the former. 
 
 For these resolutions, which were prepared by the Imperial Academy 
 and carried into execution, I must before proceeding further return my 
 sincere and grateful thanks to it, for thereby the scientific societies in 
 other countries were incited to cause accurate observations and study 
 of this important water question to be made. 
 
 2 and 3. As a result of this the Imperial and Royal Academies of 
 Sciences of St. Petersburg and Copenhagen appointed their own com- 
 missions to examine my before-mentioned treatise, which in their reports 
 on this subject, dated respectively January 22, 1876, and October 7, 
 1875, declare themselves as generally agreeing with me in my views and 
 
conclusions, but at the same time remark that a diminution in the rain- 
 fall was not established for those localities by the meteorological ob- 
 servations taken through a long series of years. The St. Petersburg 
 commission added, however, to its opinion " that it might, nevertheless, 
 be possible that a difference in distribution of the rainfall and of the 
 evaporation from the surface of the earth might cause a decrease in the 
 total amount of water in some and an increase of the same in other 
 rivers." 
 
 The same commission, referring to their observations on the results 
 of clearing lands, also mentions that in the southern parts of Russia, 
 where notoriously one hundred and fifty or two hundred years ago there 
 still existed large wooded tracts, at the present time bleak steppes have 
 developed themselves, whose elevated portions are entirely destitute of 
 water, and whose inhabitants are compelled, therefore, to settle on the 
 banks of the meager and deficient rivulets in order not to perish from 
 "want of water. 
 
 The same commission still farther adds that on the Lower Volga and 
 Dnieper the neighborhood is cleared, and that in consequence the river 
 beds Jill with sand-bars, change, and. become shallower, but that the 
 floods rise higher than formerly. 
 
 The commission of Copenhagen expresses in its reports the following 
 noteworthy opinions : 
 
 "Since in the later times our forests have not undergone any change, 
 it is difficult to substantiate the gradual decrease of water in conse- 
 quence of clearings, but we mast nevertheless add that everything leads 
 to the conclusion that at the time when Denmark was covered with large 
 forests, the volume of water in our rivers must have been far greater 
 than it is now, for there are many rivers in the country which exhibit 
 traces of having had at one time a considerable discharge, bat now 
 have only a very small one or none at all. 
 
 " That the change of woods into cultivated fields has caused a consid- 
 erable decrease in the volume of water in Danish rivers, the commission 
 can prove as an indisputable fact by the lakes near Copenhagen. 
 
 "•These lakes are situated in an extensive and flat country, the soil of 
 which consists of clay overlying a stratum of chalk. This entire plain 
 was once a forest, which has gradually partially disappeared, so that 
 some of these lakes are now found in the open fields, and the others in 
 the woods. 
 
 "The observations which were made have now established that those 
 lakes which are situated in or near woods receive a much greater vol- 
 ume of water than those of the same area which are situated in cleared 
 country, and as the other circumstances are precisely the same one mast 
 conclude that the decrease in the volume of water in the latter is to be 
 ascribed to the clearing of the woods." 
 
 The Danish commission finally expressed its opinion k ' That the de- 
 struction of forests results in a considerable decrease in the discharge 
 of rivers, and particularly in that of springs, and, furthermore, that the 
 increased cultivation of fields, and also their artificial irrigation, cause 
 a still greater decrease in the volume of water in springs and rivers." 
 
 4. The Royal Board of Canal Directors in Norway intrusted Lieut. 
 Hans Nysom with the task of collecting the data desired by the Imperial 
 Academy of Sciences of Vienna, who, in compliance therewith, in his 
 report dated Maj 20, 1877, shows that at the two water-gauge stations 
 at Nastangen and Sarpfos, on the Clommen River, which have until 
 now not been affected by any improvement of the river, the observa- 
 tions taken during thirty years confirm the theory of Mr. Wex in regard 
 
8 
 
 to decrease in the volume of water in rivers, as well as his opinion of 
 the causes of this phenomenon. 
 
 5. At my request the Society of Austrian Engineers and Architects 
 also appointed a committee of experts to give an opinion on my treatise, 
 which, in its report on this subject, made April 17, 1875, expressed the 
 following opinions, viz : 
 
 (a) The committee recognizes the vast importance of the question 
 raised by Mr. Wex, but, at the same time, the difficulties of a reliable 
 reply thereto from the observations and data which so far have been 
 laid before it. 
 
 (b) In the opinion of the committee it cannot safely be concluded that 
 because there is a decrease in the mean stage there is a decrease in the 
 discharge of a river, because if there should be a change in the cross- 
 section of discharge, or in the slope of the river, the gauges are no longer 
 reliable, and that it is, therefore, absolutely necessary that accurate and 
 regular hydraulic measurements betaken at a number of constant cross- 
 sections on the main river and its tributaries. 
 
 (c) Although the accurate measure of decrease in volume of water, 
 expressed in figures, cannot be determined from the data furnished by 
 Court Counselor Wex, yet they point to the fact that in the rivers men- 
 tioned there has been a decrease in the volume of water. 
 
 (d) The data furnished in the treatise show clearly the fact, of so 
 much greater importance to the engineer, that the regimen of the rivers 
 mentioned has lately undergone a considerable change. 
 
 (e) The causes mentioned by Wex of the hydraulic changes under dis- 
 cussion were partly combated and partly doubted in several respects, 
 and particularly the assertion that in cultivated countries the rainfall 
 has diminished by reason of the clearings ; but it was admitted that the 
 clearings had exercised a very injurious influence on the regimen of 
 rivers. 
 
 The Society of Austrian Engineers and Architects adopted the above 
 resolutions of its committee of experts at its business meeting on April 
 17, 1875, and authorized its executive committee to submit the amended 
 conclusions of the Court Counselor, Wex, to the Imperial Royal Austrian 
 Government, with the request for their execution, in order to limit the 
 threatening calamity as much as possible. 
 
 6. At the International Congress of Agriculturists and Foresters at 
 Vienna, in September, 1873, the royal Prussian inspector of forests, Dr. 
 A. Bernhardt, related, and then the royal Italian senator, Louis Torelli, 
 of Rome, submitted, very interesting data concerning the results of 
 clearings in Europe, and proved thereby that many springs fail ; that 
 the discharge of creeks and rivers at a normal stage decreases more and 
 more ; and that on the other hand floods now occur oftener and rise 
 to a greater height. 
 
 7. Mr. Torelli, particularly in his work* published May 10, 1873, fur- 
 nishes data worthy of notice, gathered from the copious hydraulic obser- 
 vations .'and notes taken in Italy, showing the injurious effects of clear- 
 ings in that country, and gives the following opinion, based upon abun- 
 dant examples and experiences, viz : 
 
 "However great may be the evils and disadvantages of the more fre- 
 quently and higher rising floods of the present time, they are not greater 
 than those which result from the progressive failing of springs and 
 decrease of volume of water in creeks and rivers." 
 
 * " Delle cause principali delle pieue dei Fiurai e di alcuni provvedimenti," per dimin- 
 nirle di Luigi Torelli, Senator del Regno. (The principal causes of high waters and 
 some measures for diminishing them,.hy Louis Torelli, senator of the kingdom.) 
 
9 
 
 Mr. Torelli further cites the following observations and measurements 
 of the distinguished expert, Paleocapa, viz: 
 
 The volume <>l* water at the lowest stage of the river Sele has decreased 
 33 per cent, during the last 150 years; that of the river Brenta, at Bas- 
 sano, 7 percent., between 1684 and 1877; and finally that of the river 
 Adda, where it flows out of Lake Como, 13 per cent., between 1842 and 
 1802 ; and this decrease still continues, and therefore creates apprehen- 
 sion. 
 
 8. In consequence of the destructive inundation of the river Po, in 
 1872, the Royal Italian Government organized a commission consisting 
 of seven experts, whose duty it was to make a minute hydraulic survey 
 of its whole valley, and, after a thorough study thereof, to recommend 
 such measures as would be suitable to prevent similar occurrences. 
 
 In the report made in December, 187G, by Mr. Basilari, vice-president 
 of the supreme board of public works, the commission expressed the 
 following opinion, viz : 
 
 The floods of the river Po have constantly increased in height, espe- 
 cially during the present century, in consequence of which it became 
 necessary to raise and strengthen the greater portion of its levees. 
 This method of relief was considered by the commission not only as in- 
 adequate, but as really increasing the danger, for which reason it was 
 led to consider means by which the height of these floods could be di- 
 minished, or, at least, the increase stopped. Consequently it examined 
 into the condition of the forests in the valley of the Po. It laid great 
 weight on the enactment of suitable laws against destruction of forests ; 
 recommended next the construction of large reservoirs for the storage 
 of a portion of the floods, which might subsequently be used for irriga- 
 tion; further proposed the construction of suitable works for improving 
 the mouths of its tributaries; and finally recommended several cut-offs, 
 in order to diminish the length of the stream. 
 
 The preceding opinion and the proposed measures therefore fully coin- 
 cide with the views expressed in my treatise of April, 1873. 
 
 9. Professor Dr. Ebermayer, in his admirable work entitled " Physika- 
 lische Einwirkungeu des Waldes auf Luft und Boden und seine klimat- 
 ologische und hygienische Bedentung begriindet durch die Beobacht- 
 ungen der forstlichmeteorologischen stationen in Kdnigreich, Bayern. 
 Aschaffenburg, 1873,"* has furnished convincing proof of the following 
 statements, based upon minute scientific experiments and observations 
 during many years, viz: 
 
 (a) The forest influences the amount of rainfall by increasing the 
 relative humidity of the atmosphere and bringing it nearer the point of 
 complete saturation, so that when the temperature is lowered a partial sep- 
 aration of the water takes place more easily and in greater quantity 
 than in clearings. This influence is more marked in proportion to the 
 height of the forest above the level of the sea. 
 
 (b) The forest diminishes the evaporation of the surface water in a 
 much greater degree than an open field. In those whose grounds are 
 kept clean it amounts to 02 per cent., and in the others to 08 per cent. 
 
 (c) In the interior of the continent, where the humidity of the atmos- 
 phere and annual rainfall decrease and the degrees of summer heat 
 increase, the forest has a greater influence on the rainfall than in the 
 coast regions. Ireland and Great Britain can dispense with their forests 
 more easily, as far as rainfall is concerned, than Germany or Russia. 
 
 *The physical effect of the forest on the atmosphere and soil, and its climatological 
 and hygienic importance, based upon observations made at the foresters' meteorologi- 
 cal stations in the Kingdom of Bavaria. Asohaffenburg, 1873. 
 
10 
 
 (<1) Large clearings in level countries have material influence, it is 
 true, but in billy regions there will be, on an average, less rainfall than 
 before, and especially in the warmer half of the year. 
 
 Even if it were assumed that, after clearing forests, under all circum- 
 stances, the rainfall would be the same as before, the enormous influ- 
 ence of the forest, and its ground covered with leaves and brush upon 
 the evaporation of its surface w r ater, in consequence of which, compared 
 to the surrounding country, it must be considered a great reservoir, 
 would sufficiently explain the well-known fading of springs aud its influ- 
 ence in diminishing the medium stages of the rivers. 
 
 (e) There is another fixed relation between the stage of water in 
 rivers and the forest caused by the fact that in wooded localities the 
 snow lies three or four weeks longer and melts less rapidly than in clear- 
 ings. In an open country the rise in rivers occurs more rapidly after 
 the melting of the snow; the latter runs off more rapidly, less soaks into 
 the ground, and the springs are therefore fed less than in wooded coun- 
 tries. 
 
 (/) Extensive clearings are more injurious in hilly than in level 
 countries. They produce in a short time destructive torrents, dry 
 periods, then short but destructive inundations, formation of sand-bars 
 in rivers, want of perennial springs and creeks, and great variations in 
 the stage of the rivers. These most certainly occur and characterize 
 such regions in which the hills have been cleared. 
 
 Mr. Ebermayer says, finally, viz: 
 
 (g) " If we combine the different effects of the forests, there can be no 
 doubt but that their disappearance must considerably diminish the 
 volume of water in a country, even if after the clearing there is as much 
 rainfall, as before." 
 
 " The preceding statements show how closely the wealth of forests and 
 water in a country are bound together ; a circumstance which is partic- 
 ularly due to the x^owerful influence which the forest and its ground 
 covered with leaves and brush has upon the evaporation of the moisture 
 in the ground. It is, then, not to be wondered at that springs and 
 creeks dry up or flow only periodically ; that the mean stage of rivers 
 and creeks diminishes in height when large clearings are made in a 
 country, and that on the other hand springs flow more copiously and 
 regularly when new trees are planted and forests are increased in extent." 
 
 10 and 11. The imperial chief forester, Edward ISTey, of La Brogue, in 
 Alsace, in a paper published in January, 1875, entitled " Ueber den Ein- 
 fluss des Waldes auf die Bewohnbarkeit der Lander,"* and Dr. Jacob 
 von Bebberer, in his paper published in 1877, entitled " Die Begenver- 
 haltnisse Deutschlands,"t both written after observations made during 
 a long series of years, on the great influence of the permanence of forests 
 on the hydraulic condition of countries, have expressed precisely the 
 same opinions as Professor Ebermayer. 
 
 As an illustration of the fact that the clearing of hilly countries fre- 
 quently results in the complete fading of springs, Mr. ISTey mentions 
 that in the Provence, after all the olive-trees, which there formed regular 
 forests, had been frozen in 1822 and cut down, a great number of springs 
 failed totally, and that besides, in the city of Orleans, after the surround- 
 ing heights had been thus cleared, nearly all the wells dried up, and it 
 became necessary to conduct the headwaters of the river Little Loire 
 into the city. 
 
 Mr. Key furnishes the following examples to prove that during the 
 
 * " Concerning the influence of the forest on the habifcableness oi" countries." 
 t " The circumstances relating to rain in Germany." 
 
11 
 
 historical period many rivers once rich in water supply have become 
 much poorer therein, notwithstanding their more frequent floods in con- 
 sequence <>f the destruction of the forests, viz: 
 
 At the time of* the Roman rule in France, the river Durance, south of 
 Avignon, and the Seine were navigable rivers and richly supplied with 
 water, so much so that the navigators of the Durance formed an in- 
 fluential corporation, and Emperor Julian, who resided in Paris during 
 a period of six years, particularly extols the constant even stage of the 
 Seine. At present, since the regions of the headwaters of these two 
 rivers have been cleared, the Durance can hardly float a skiff in summer, 
 and the Seine, in which the difference between the high and low water 
 stage is now 32 feet 10 inches, was only made navigable again by the 
 construction of numerous wing-dams. 
 
 12. The director of the royal board of foresters of Hanover, Dr. Burck- 
 hardt, in a letter addressed to me on March 5, L876, says the views ex- 
 pressed by me in my treatise were expressed in words which were as if 
 taken from his own soul, and that he had also, in the course of his ob- 
 servations extending through a period of twenty-live years, seen the 
 sad results confirmed that in consequence of the clearings made in North 
 Germany there resulted the disappearance of many lakes and ponds, 
 draining of marshes, failing of many springs and creeks, and the lower- 
 ing of the surface water, whereby the cultivation and productiveness of 
 the remaining fields suffered sadly. 
 
 13. Prof. Alexander Bettochi, inspector of the Royal Corps of Civil 
 Engineers at Rome, in his memoir submitted to the Royal Academy, 
 "dei Lincei," in June, 1876, which was subsequently published as a 
 paper, acknowledges that my theory relative to the diminution of water 
 in springs and rivers contemporaneously with the increase in height of 
 floods agreed with observed results, and still further substantiated it by 
 plotted observations made on the Theiss at Szegedin. 
 
 14. Mr. Frederick Symong, imperial and royal professor of geography 
 at the University of Vienna, honorably known by his researches and 
 surveys in the Alpine regions, in his lecture entitled "Schutz dem 
 Walde,"* given February 21, 1877, before the Society for the Diffusion 
 of Knowledge of Natural Sciences, at Vienna, acknowledged my theory 
 as being correct, and at the same time proved conclusively that in con- 
 sequence of the destruction of the forests in mountainous regions the 
 rainfall diminishes at those points, vegetation on the mountain sides is 
 constantly receding, the soil is washed off, after which the mountains 
 gradually become perfectly barren. A further result of this is a decrease 
 of water in the lower strata, in springs, creeks, and rivers, which in turn 
 are succeeded by the drying up of the valleys, and the gradual devasta- 
 tion of cultivated fields, thus proving the truth of the saying of a great 
 naturalist, "Man strides over the earth and a desert follows him." 
 
 15. Dr. F. W. Dunkelberg, director of the Royal Agricultural Academy 
 at Popelsdorf, in his work entitled "Die Schiffarths-Canale in ihrer 
 Bedentung fur die Landes Melioration"! (Bonn, 1877), concurs with 
 me in my theory relative to the decrease of water in springs and rivers, 
 it being the result of his own observations and experience. 
 
 1G and 17. Further along during my discussion of the observed results 
 on the Elbe, 1 will give the concurring views of Mr. M. W. Schmidt, of 
 Dresden, royal director of hydraulic works, and of Mr. Maass, of Magde- 
 burg, a member of the royal board of public works. 
 
 * Protect the forest. 
 
 tThe importance of navigable channels in the improvement of countries. 
 
12 
 
 18. Mr. Robert Lauterburg, the Swiss engineer and hydraulic expert, 
 who occupies a great deal of his time in collecting exact data and in 
 comparing the relative discharge of the rivers of Switzerland, in his 
 paper entitled " Ueber den Einfluss der Walder auf die Quellen und 
 Stromverhaltnisse der Schweiz"* (published by Schulze at Basle, 1877), 
 announces the following very reliable results of his surveys, viz : 
 
 In the Melasse formation within an area of .29 of a square mile the' 
 relative discharge of springs was accurately measured, and it was found 
 that those in wooded portions discharged from five to ten times the 
 amount of those in the clearings. 
 
 Now, as it is universally known that during those periods in which for 
 weeks there is no rain the creeks and rivers are almost exclusively fed 
 from the springs, filtration, and surface water, and also knjwn that 
 since the introduction of railroads and telegraphs in Europe, as well as 
 the general and extraordinary increase in all kinds of manufactures and 
 trade, such a colossal consumption of building and fire wood has taken 
 place that in Europe several million hectares f of forest which formerly 
 existed, and particularly in hilly regions, have been cut down and de- 
 stroyed, it can be concluded in advance, from the result of these obser- 
 vations in Switzerland, and without giving the gauge readings on rivers 
 and streams the least consideration, that during the last forty years the 
 discharge of springs, creeks, and rivers, during low and medium stages, 
 must certainly have decreased. 
 
 Now, I will take the liberty of showing that not only in Europe, but 
 in the cultivated portions of other parts of the world, the discharge of 
 their rivers and streams has also decreased during the last decade. 
 
 19. In a report made to the House of Representatives on March 14, 
 1874, the Commissioner of Public Lands of the United States of America 
 expressed his fear that the continued destruction of the forests would 
 seriously injure the public interests. At the request of the Commis- 
 sioner to submit this important question to thorough experts, the Ameri- 
 can Academy of Sciences charged a committee composed of several of 
 its members with the task. After the committee had collected accurate 
 data and given the subject mature deliberation it made an extensive re- 
 port, full of statistical information, from which I will quote only the 
 following chief points. 
 
 The committee in this report recounts the bearing and importance of 
 forest culture not only for timber, but also as a means of improving the 
 general welfare, as the climatic conditions depend upon the existence 
 of forests and deteriorate with the destruction of the latter. 
 
 The evident results of the destruction of forests are " the failing of 
 springs, drying up of creeks, decrease in volume of water in the rivers, 
 canals, and streams, and the increasing difference between high and 
 low water stages in the latter." The fact that the volume of water in 
 rivers and streams decreases in proportion to the destruction of the for- 
 ests will not escape any careful observer, and America is threatened 
 with the danger that changes will take place in the permanence of its 
 largest rivers even, fraught with the most serious results, unless suitable 
 measures are adopted in proper time. 
 
 The committee finally enumerated and recommended measures and 
 precautions most suitable to stop this threatening calamity, which are 
 nearly the same as those which I proposed in my first treatise of 1873. 
 
 Congress, appreciating these suggestions, passed an act dated August 
 
 * On the influence of forests on the conditions of the springs and streams of Switz- 
 erland. 
 
 t About two and one-half acres. 
 
13 
 
 15, 1876, appropriating $60,000 tor the purchase of seeds and plants and 
 generally for the improvement and promotion of forest culture; and a 
 further sum of $2,000 as a prize to an expert in The investigation of the 
 question of forest and tree culture and the means which best commend 
 themselves for the preservation, improvement, and planting of forests 
 in North America.* 
 
 20. The above prize was won by Dr. Franklin B. Hough, through his 
 scientific workt on this subject, in which he points out in great detail 
 the influence of forests on the even and seasonable rainfall, upon the 
 acquisition of a regular water supply to the springs, creeks, and rivers, 
 and finally on the prevention of extraordinary Hoods, and in which he 
 then cites the p roofs furnished by my treatise of April, 1873, and agrees 
 with me in the views therein expressed and with the theory concerning 
 the decrease of water in springs and rivers as therein announced. 
 
 It will be seen from the official proceedings and the scientific data 
 which have been collected, as just meutioned, that already in North 
 America even, where, partly through the vandalism, ignorance, or 
 avarice of the inhabitants and partly through elemental disturbances, 
 very extensive tracts of wooded lands have been cleared and totally de- 
 stroyed, the highly injurious effect thereof, and particularly the decrease 
 in the volume of water in their springs and rivers, probably has become 
 more evident than to us in Europe, and that also the government of that 
 country has forthwith recognized the danger resulting from this not only 
 to its present but also to its future generations, and that it now proposes 
 to apply in the most energetic manner such measures as will prevent 
 this danger as much as possible. 
 
 21. The only knowledge which I have thus far obtained relative to 
 to this question in South America is taken from the following article, 
 dated December 5, 1878, written from Rio Janeiro to the Colnische 
 Zeitung, | viz : 
 
 "A phenomenon is developing which causes apprehension on the part 
 of the inhabitants on the banks of the Amazon, namely : The stream is 
 receding in an appalling manner, and particularly above Mauaos navi- 
 gation is already impossible. There is a constant decrease in the stage 
 of the river, the causes of which are wholly unknown. It is very de- 
 sirable that thorough naturalists should examine this phenomenon." 
 
 Now, if such a remarkable decrease iu the volume of water has been 
 observed in the upper portion of the Amazon, which is the largest and 
 has a greater wealth of water than any other river on the face of the 
 globe, it is very probable that similar decrease in the volume of water 
 has taken place in the other rivers and streams of South America, and 
 that this cannot be substantiated for want of observations alone. 
 
 22. Mr. John Croumbie Brown, the distinguished naturalist, formerly 
 professor of botany at Cape Town, in his book entitled "Hydrology of 
 South Africa, compiled by John Brown, LL.D., Kirkcaldy, printed by 
 John Crawford, 201 High street, 1875," has published very interesting 
 
 *The author is mistaken herein. The. act approved August 15, 187(i, directed the 
 Commissioner of Agriculture to appoint some man of approved attainments and prac- 
 tically well acquainted with the methods of statistical inquiry, with a view of ascer- 
 taining the annual amount of consumption, importation, and exportation of timber 
 and other forest products, the probable supply for future wants, &c. On August 30 
 187G, Hon. Frederick Watts, then Commissioner of Agriculture, appointed Dr. Prank, 
 lin B. Hough, of Lowville, Lewis County, New York, to the discharge of this impor- 
 tant duty. 
 
 t Report upon forestry, prepared under the direction of the Commissioner of Agri- 
 culture, in pursuance of an act of Congress approved 15th of August, 1876, by Frank- 
 lin B. Hough. Washington, Government Printing Office, 1878. 
 
 t Cologne Gazette. 
 
14 
 
 observations and experiences, extending through a long series of years, 
 concerning the former and present condition of the countries as well in 
 Africa as in the larger islands of the Southern Ocean, of which I will 
 briefly mention but a few. 
 
 In South Africa there are yet found scattering groups of trees of 
 gigantic dimensions and great age, but without any corresponding after- 
 growth, which are undoubtedly the remnants of former extensive forests 
 which were cleared or destroyed by tire. These ancient gigantic trees 
 prove the former great humidity of the climate and the rank fertility of 
 the soil. 
 
 The destruction of the forests in South Africa and the custom which 
 prevails there of destroying their tall grasses by fire have contributed very 
 much to the parching of the soil in those localities, so that new trees are 
 only found along the banks of rivers and in high mountain passes. 
 
 Dr. Livingston and Dr. Moffat also describe the burnings just men- 
 tioned, and the~latter refers to an extensive forest of wild olive trees in 
 the vicinity of the city of Griqua which was destroyed by tire, and men- 
 tions the gradual decrease of rainfall which resulted therefrom. 
 
 Mr. Brown notes many observations concerning the numerous and 
 sudden changes which occur at present from severe droughts to violent 
 rains, causing destructive overflows and the evident decrease in the vol- 
 ume of water, indeed the complete drying up of many creeks and rivers 
 as well as their change into torrents; which, however, are only created 
 when the forests and plants of the mountain slopes were destroyed and 
 the soil was washed away in consequence thereof. In countries where 
 mountains are covered with forests no torrents are formed, but, on the 
 contrary, plenty of springs, creeks, and rivers, which serve to increase the 
 fertility of the soil. 
 
 The author further reports upon the decomposition of the former rich 
 soil by the sun's rays, by which the country becomes sterile, and the 
 .fields which were once rank are converted into deserts, and says that 
 these very disastrous changes are, according to the scientific investiga- 
 tion of Mr. Brown and a naturalist cited, by him, entirely due to the 
 destruction of the forest in those countries. 
 
 In the concluding chapter of his work Mr. Brown recommends, for the 
 purpose of removing or at least ameliorating the evils which have re- 
 sulted from the destruction of forests, measures and precautions almost 
 identical with those proposed by me in my first treatise of 1873, although 
 the latter was unknown to him when he compiled his work. 
 
 In the second work published by Mr. Brown, entitled "Forests and 
 Moisture, or Effects of Forests on Humidity of Climate, compiled by John 
 Croumbie Brown, LL.D., Edinburgh, 1877," he proves conclusively, inmore 
 detail, not only theoretically but also by numerous illustrations, the fact 
 that forests have a great influence and effect on the humidity of the air 
 and surface of the earth, the drying up of marshes, the formation of 
 clouds, on the quantity and regular distribution of rain among the different 
 seasons, and the discharge of springs and rivers. In this work Mr. Brown 
 cited the data collected in my treatise of 1873, and declares himself as 
 agreeing with me in my theory concerning the decrease of the volume of 
 water in springs and rivers. 
 
 23. In conclusion, I must here advert to a fearful catastrophe which 
 lately occurred, and strikingly proves the disastrous results of unlimited 
 destruction of forests. 
 
 The northern province of the Chinese Empire, Shan-Si, whose capital 
 is Tayeun, is inclosed on all sides by high mountain ranges, which in 
 early ages were covered with dense forests. At that time it rained here 
 
15 
 
 every year periodically, the atmosphere was sufficiently humid, and it 
 belonged to the fertile, well-cultivated, and densely-settled provinces of 
 
 the Chinese Empire. But the inhabitants of this once blooming and 
 happy country, through greed and in the endeavor to increase the yield 
 of these mountain slopes more and more, have gradually cleared the 
 surrounding mountains completely. The result is that the former pe- 
 riodical rains have almost disappeared, and that the rainfall as well as 
 the humidity of the atmosphere have decreased, and that, consequently, 
 in this province failure of crops, want, and misery have succeeded each 
 other during several years, in 1877, already, there was such a general 
 drought, failure of crops, and famine, that in consequence thereof nearly 
 three millions of souls perished. In the official report of the governor, 
 Li Ho-nien, chief commissioner of the board of relief, the following 
 account of this catastrophe appears, viz: 
 
 " During the first period of this unheard-of famine, the living sub- 
 sisted upon the corpses of the dead ; then, later, the weak were devoured 
 by the strong ; now the misery has reached such a stage that the peo- 
 ple devour their own blood relations. History, up to this date, has not 
 shown a more horrible state of affairs than this, and unless measures 
 for relief are promptly taken the entire population of this section of 
 the country will be destroyed." 
 
 The Catholic bishop, Monagatta, in a letter from Tayeun, dated March 
 21, 1878, corroborates the description contained in the above report of 
 the horrible scenes enacted during the famine. 
 
 The ruinous results of the destruction of forests are also showing 
 themselves in the other provinces of China; in the highlands by killing 
 droughts, and simultaneously in the southern lowlands of the empire by 
 destructive rains and overflows. 
 
 C H A P T E R I I . 
 
 Clearing up the doubts axd rerutting the arguments oe the opponents to 
 my theory on the decrease oe water in springs and rivers, axd communi- 
 cating the new data and observations relating thereto collected by 
 ME si xci', L873. 
 
 So far as I have been able to learn, up to the present time, from pub- 
 lished works and scientific periodicals, the following engineers and ex- 
 perts have expressed views in opposition to my theory, viz : 
 
 1. The committee of experts of the Society of Austrian Engineers 
 and Architects, which, in its report already referred to by me, agrees 
 with my theory in general, but doubts somewhat the proofs which I 
 offered and the conclusions drawn therefrom. 
 
 2. Mr. Sasse, royal Prussian ministerial counsellor and member of the 
 board of public works (Zeitschrift fur Bauwesen, von C. Erbkain, in 
 Berlin, von Jahr 1871). * 
 
 3. Mr. Kluge, royal Prussian inspector of hydraulic works (in the 
 journal just mentioned). 
 
 4. Mr. Schlichting, royal Prussian inspector of hydraulic works 
 (Deutsche Bauzeitung, Jahr L876). t 
 
 5. Mr. Grebenau, member of the imperial board of achitecture and 
 director of hydraulic works (Deutsche Bauzeitung, Jahr 187G.) t 
 
 * Journal of Architecture, Berlin, 1874, G. Erbkam, publisher. 
 
 t German Gazette of Architecture, 187b\ 
 
16 
 
 C. Mr. Grave, royal Prussian district architect and deputy director of 
 public works (Deutsche Bauzeitung, Jahr 1877.) t 
 
 7. Mr. Charles Hurich, royal Hungarian ministerial counsellor (Zeit- 
 schriftdes ungarischen Ingenieur und Architecten Yereines.) * 
 
 8. Dr. Joseph Bitter Lorenz von Liburnan, imperial and royal minis- 
 terial counsellor (Wald, Klima, und Wasser, 1878.) t 
 
 These opponents urged against my theory and the proofs on which it 
 rests the following doubts and arguments in general, viz: 
 
 A. That the decrease in the stages of water, i. e., the lowering of the 
 water surfaces shown by me to have taken place at the nine gauges on 
 the five rivers may not have resulted from a decrease in discharge, but 
 from a deepening of the river beds or a change in the slope caused by 
 works of improvement. 
 
 B. That the established fact that the stages of these rivers have de- 
 creased in height does not furnish reliable x^roof that their discharge 
 has decreased. 
 
 C. That it may be possible that the increased discharge of streams, 
 produced by the higher floods of the present time, brings the decreased 
 discharge caused by the diminished height of low and medium stage to 
 the former general average, and then the observations furnished would 
 only show that during the last decade the regimen of rivers and streams 
 has undergone a change. 
 
 D. That gauge readings of a stream extending through a period of at 
 least 200 years are necessary in order to draw a reliable conclusion from 
 them whether a decrease in volume of water has really taken place or 
 not. 
 
 E. That it cannot be determined with certainty from a comparison of 
 the heights of different stages of streams whether a decrease in the vol- 
 ume of water has taken place or not, and that this can only be done by 
 directly measuring, from time to time through a long period of years, 
 the actual discharge of rivers and streams. 
 
 F. That the assertion made by me that the amount of rainfall had 
 decreased in consequence of the great devastation and destruction of 
 forests is not at all proven by the examples which I furnish, and the 
 opinions of scientific authorities which I cite, because from meteorolog- 
 ical observations extending through a long series of years in Eugland, 
 at Paris, St. Petersburg, and Copenhagen it cannot be deduced that 
 the rainfall has diminished. 
 
 G. Mr. Grebenau declares that my theory relating to the decrease of 
 volume in water is incorrect, and advances instead the new theory that 
 the beds of creeks, rivers, and streams, are continually deepened by the 
 erosive power of the running water, and that alone in consequence of 
 this deepening, the heights of the water stages constantly decrease, i. e. 7 
 the water surface of rivers and streams sinks deeper and deeper. 
 
 Since Mr. Grebenau declares my theory incorrect, and substitutes 
 therefor one which is entirely new in hydraulics, I propose, first, to 
 thoroughly discuss the arguments and proofs upon which it is based, 
 because, in case his assertions and theory should be well founded, the 
 discussion of the other doubts and objections can be dispensed with. 
 
 In consequence of the invitation heretofore mentioned, given by the 
 Imperial Academy of Sciences of Vienna, to all foreign scientific insti- 
 tutions, Mr. Grebenau, among others, was requested to give his opinion 
 of my treatise on the decrease of water in rivers and streams, based upon 
 his observations and experience relating to this subject. 
 
 * Journal of the Society of Hungarian Engineers and Architects, 
 t Forest, climate, and water. 
 
17 
 
 Upon this, Grebenau, with his characteristic tireless diligence and 
 energy, collected tin' gauge readings of fourteen largerri vers and si reams, 
 compared them, combined them in various ways, at the same time 
 studied zealously the water question raised by me, and then gave a 
 del, died lecture as the results of his investigations, on September <», 
 1876, at the general meeting of the Union of Societies of German En- 
 gineers and Architects, held at Munich, on the "Sinking of rivers, and 
 the phenomena accompanying it." in which he communicated the follow- 
 ing, viz*: He compared the readings of 75 gauges on 11 rivers lor low, 
 medium, and high water stages, divided them into two periods of ob- 
 servations, similar to the manner in which Mr. Wex did, calculated the 
 mean of these, compared them, and, assuming that the mean of the 
 observations at the above-mentioned stages need always only be taken 
 into consideration, obtained the following results, viz: 
 
 The medium stage of 12 rivers, supplied with 67 gauges, receded, i. e., 
 the surface of the water sank, on an average, from •"> feet 3f inches, 
 to <> feet 6| inches; on the contrary, the stages of 4 rivers at 6 gauges 
 increased in height, and, indeed, just at those at which the half periods 
 of observation were very short, they lasting only 7, 7i, 12i, and Id J, 
 years. 
 
 From the results of these observations Grebenau concluded that in the 
 changes which take place in the fall and rise of the river at several 
 gauges on the same river at the same time of observation when the dis- 
 charge is nearly uniform, no decrease in the volume of water can be 
 substantiated, because if the fall of the river shown by the reading of one 
 gauge would indicate a decrease, a rise shown at another gauge of the 
 same river would indicate an increase in the volume of water, which 
 clearly is impossible. 
 
 "Now. as 31r. Wex admits in his treatise that on several rivers, and 
 particularly at nine gauge stations on the Danube, the bed of the river 
 either raised or sunk, his theory that a decrease in the height of stages 
 of a river or a sinking of its surface indicates a decrease in the volume 
 of the water becomes, through this admission alone, untenable." 
 
 Grebenau further remarks concerning my theory that the great amount 
 of the decrease in the stages of several streams established by the figures 
 given in my treatise prove that this cannot be the result of a decrease 
 in the volume of water, because otherwise these streams would in sev- 
 eral hundred years be without water and their beds dry. 
 
 In reply to these conclusions of Grebenau, 1 believe it to be my duty 
 to make the following explanation : 
 
 It 'is certainly generally known that the beds of rivers and streams 
 which are not yet improved, or on which the improvements have just 
 been begun, are deepened in some stretches and raised in others by the 
 forma' ion of bars, and that therefore in consequence of this a sinking or 
 raising pf the water may occur, from which no reliable conclusions could 
 be drawn. 
 
 lint if, from the numerous gauge readings which are submitted by me 
 are eliminated those which were taken on stretches of the stream in 
 which changes in the bed of the river took place, we will still find some 
 rivers or stretches of streams which lie either in a natural unchangeable 
 
 "An abstraci of tin- letter was published in the German Gazette of Architecture, o:' 
 toiler 21, 1876. Grebenau had more extensively elaborated his investigations in the 
 water question, ami had prepared them for publication when, unfortunately, too 
 soon death tore him away on June 23, 1-7T . His highly-respected widow was so kind 
 as to transmit to me the manuscript for inspection; but our united efforts to publish 
 it were vain, in consequence of the accessary expense, which was considerable. 
 
 2 w 
 
1* 
 
 bed or which have been improved from time immemorial and are in a 
 permanent condition. The most scrupulous expert must admit that on 
 such rivers and stretches we can justly assume that the decrease in 
 their stages, i. e., sinking of their surface, indicates a decrease in the 
 volume of water, since it would be impossible to explain the phenomenon 
 in any other way. 
 
 I must remark concerning the second objection of Grebenau to my 
 theory that in my first treatise of 1873 I only expressed the apprehen- 
 sion lest the creeks and rivers, still replete with water, which exist in 
 cultivated countries might, gradually, during a larger part of tin 1 year 
 have little discharge ; but, on the contrary, after heavy rains swell fear- 
 fully and become converted into torrents. 
 
 It is a historically-established fact that such changes have already 
 taken place in the cultivated countries of ancient times, and only those 
 can doubt it who are unacquainted with the geography and history of 
 those countries. 
 
 It is out of the question to suppose that a stream which is created by 
 the confluence of many creeks and rivers can ever completely dry up, 
 because, although the rainfall is diminished by clearings, yet it will 
 never completely have an end, and because in a large river valley the 
 springs, creeks, and tributary rivers can never lose their water simul- 
 taneously, since the rainfall is irregularly divided among the valleys of 
 the different creeks and tributary, rivers, and the high water of the one 
 frequently reaches the main stream simultaneously with the low water 
 of another. The change of the tributaries into torrents cannot there- 
 fore completely dry up the main stream, but it may cause great and 
 numerous variations in its stage, which might become excessive. It is 
 clearly apparent from the plot of gauge readings given in my first treatise 
 that this change has already begun in several streams of Europe. 
 
 I believe that I have thus successfully controverted the objections 
 brought forward by Grebenau against my theory, and I will now pass 
 to a closer examination of the new theory established by him. 
 
 Grebenau, as already stated, pointed out a considerable decrease in 
 the lower, medium, and higher stages, ?. e., a sinking of the water sur- 
 face of 12 rivers at 67 gauges, and explained this remarkable phenom- 
 enon by the following new theory, viz : 
 
 The mountains on the surface of the earth are being continually re- 
 duced in size by washings caused by the working power (called by later 
 geologists the power of erosion) of running water and the adjacent de- 
 pressions or valleys filled up and elevated. Grebenau then sets up the 
 following thesis on the effect of this power of erosion of running water 
 on the beds of streams : 
 
 1. The mud which is created when a river rises is due to the friction 
 of the different kinds of debris upon each other, and the floating mud 
 is therefore the necessary result of the rolling debris. 
 
 2. This mud is generated and carried farther at each point when 
 there is rolling debris, and, therefore, increases continually in a down- 
 stream direction ; and, indeed, according to the rule of arithmetical 
 progression. 
 
 3. The voids produced in the debris by the mud thus carried off are 
 the causes of the continued and lasting deepening of the river bed and 
 the resulting sinking of the water surface. 
 
 Grebenau, assuming these theses as established in discussing the 
 Khine, whose water surface in Alsace, as he proves, sinks on an average 
 .64 of an inch annually, and, therefore has sunk 5 feet 4 inches during: 
 
19 
 
 100 years, and 53 feel 4 inches during the last L,000 years, arrives al the 
 conclusion that aboul 5,900 years ago the falls at Schaffhausen did n<»t 
 exist, and have only been caused since that time by the sinking of the 
 bed of the stream below, and thai about L,000 years ago the surface of 
 its central portion below B. isle was at the height of its present high 
 banks, or 53 feet 4 inches higher than it is, and that it then washed and 
 tunned these hanks and since then has deepened its bed and lowered its 
 water surface to that amount. 
 
 If the theory of Grebenau that the beds of all rivers and streams 
 are deepened by the power of erosion at a continuous rate of § to v of 
 an inch annually — consequently from '■'> feet U inches to C> feet :; inches 
 in 100 years, and from 31 feet ;; inches to 62 feet 6 inches in 1,000 — were 
 considered well founded and true, it would have a very injurious effect 
 upon the cultivation of countries ami future generations. I have, there- 
 fore, since 1S7<;. collected data and studied the question in the most 
 thorough manner, ami 1 take the liberty to communicate briefly the 
 result thereof. 
 
 It is known to every hydraulic engineer and geologist that rivers and 
 stie.ns flowing througb large broad valleys, if left to themselves, do 
 not <h epen their beds, which consist of coarse rounded gravel and dSbris. 
 but cause their banks, which consist of lighter earthy material, to cave 
 in, largely increase the width of their beds, create islands, 1 tends, and 
 swift currents, and finally, as they lose through this the most of their 
 transporting power, the debris from the regions of their headwaters and 
 tributary creeks and rivers is deposited and raise their beds. 
 
 During past ages these wild rivers and streams meandered at will in 
 the valleys, and created their existing hanks by tilling up the deep 
 gulleys and basins of the sea which previously existed. At the present 
 time these wild streams raise their banks by deposits of mud during 
 overflows, hot not as rapidly as their beds are raised, and it frequently 
 lia. pens that the difference of level between tin- banks and bed of the 
 river is diminished and the height of overflows increased. 
 
 It is also very well known to every experienced hydraulic engineer 
 that the velocity and motive power of these wild streams can be so much 
 increased by their improvement, i. «>., by narrowing its wide stretches, 
 closing subsidiary channels, making cut-offs, and finally protecting its 
 banks, thus increasing their slope : that the beds of these improved por- 
 tions will he gradually deepened by the removal of the p 'boles and 
 debris which raised them, and that they will be enabled to move the 
 debris which is brought from the region of the headwater by high 
 waters farther down stream. If, however, this improvement is not 
 made throughout the whole stream this debris will be deposited in the 
 lower parts thereof, and thus raise its bed and cause it again to run 
 wild. 
 
 The fact just mentioned that rivers and streams, in their natural state, 
 have a tendency to raise their beds, and consequently their water sur- 
 face, and that a deepening of the former and lowering of the latter can 
 only result from their thorough improvement, has been already men- 
 ti >ned in a detailed manner by Mr. Hagen, royal Prussian privy coun- 
 selor of the superior board of public works, in his admirable manual 
 on the knowledge of hydraulic works, and many more of the distinguished 
 hydraulic engineers of Germany and Italy who 1 requested in writing 
 to give me the result of their observations on this point have declared 
 that after many years devoted to the study thereof they consider this 
 an established fact, ami none of them could furnish me with a single in- 
 
20 
 
 stance in which the bed of a river or stream was continually deepened 
 by the natural power of erosion of the running water. 
 
 Although it must be admitted that the friction of the particles of gravel 
 brought down by high water against each other does cause some mud, 
 yet it must be clear that by far the greatest part of that carried along 
 by high water is produced by the rain washings of the valleys, by caving 
 of unprotected banks, and finally by the debris, sand, and earthy matter 
 emptied into the stream by its tributary creeks and rivers, so that a 
 deepening of the bed cannot be even inferred from the quantity of sand 
 carried off by a stream, much less can it be measured thereby, bo- 
 cause that which is produced by the friction among the particles of 
 debris is vastly overweighed by the very large quantity of rubble sand and 
 earth which is brought in at every high stage from the headwaters 
 and tributaries. 
 
 From this it follows that the theory advanced by Grebenau that the 
 mud transported by the high water of streams is principally created by 
 the friction of the particles of debris on each other, and its sequence 
 that the beds of old rivers and streams are continually deepening 
 through the power of erosion of their running water, is evidently incor- 
 rect, since in all rivers and streams in their natural state precisely the 
 opposite, namely, the raising of the bed, takes place. 
 
 The incorrectness of the theory advanced by Grebenau is also proven 
 by historical facts, for if the deepening of river beds had continually 
 taken place in earlier times all valleys whose surfaces are now only from 
 6 feet Of inches to 9 feet 10^ inches above the medium stage of the river 
 must have been permanently inundated about 500 years ago, which 
 plainly was not the case, because at that time cities and many inhabit- 
 ated places existed therein. Mr. Grave in his criticism of Grebenau's 
 theory* (Deutsche Bauzeitungvon Jahr, 1S77,1N"os.51 and 56) has already 
 proven at considerable length the fact that it was opposed to historical 
 facts. 
 
 I can leave the contradiction of Grebenau's theory concerning the 
 creation of the falls of the Rhine by reason of the sinking of the river 
 bed below to the geologists, who are better versed in such a subject, but 
 I must, on the other hand, opppose in a determined manner is further 
 assertion that about 1,000 years ago the water surface of the Rhine below 
 Basle was on the same level with its high banks, and that it made these, 
 and since that time its bed has been deepened about 53 feet 4 inches. 
 
 Grebenau, at the general meeting of the " Pollichia," in Durkheiin, 
 delivered a lecture, on September 11, 1S69, entitled "Der Rhein vor und 
 nach seiner Regulirung," t which was subsequently published as a paper, 
 with maps and profiles attached, which proves, at great length and very 
 thoroughly, that in prehistoric times there existed, in the present valley 
 of the Rhine, between Basle and Bingen, a large sea which gradually 
 flowed off, as the mountain gorge between Bingen and Bonn Avas formed. 
 The basin of this sea was filled up by the large masses of rubble and 
 debris brought into it, not by the Rhine alone, but also by the creeks and 
 other rivers which emptied into it, to within from 32 feet 9f inches to Q5 
 feet 7 1 - inches of the present surface of the valley. The high banks, 
 also called the Dilurian terraces, which are from 3.1 to 4.3 miles apart 
 and 32 feet 9 inches in height, were clearly once the rim of this basin, 
 and received their present form partly through the action of the waves 
 of this sea, which subsided very slowly and in proportion to the crown 
 
 * German Gazette of Architecture, 1877, Nos. 54 and 56. 
 tThe Rhine before an 1 after its improvement. 
 
21 
 
 of the rocky crest of the Calls at Bingen, and partly to the undermining 
 caused by the Rhine, which meandered in this irregularly filled-up basin 
 
 in the wildest maimer. Since the basin lias filled, up, and after the slope 
 had become regular between the crest of the overfallat Bingen and the 
 river bed, also consisting of rock, at Basle and at Waldshut, the Rhine 
 
 has not only not lowered its adjacent hanks, which are composed of 
 coarse gravel, hut on the contrary has raised them from 3 feet 3§ inches 
 to »> feet 6| inches, by depositing upon them sand and mud during its 
 frequent overflows. 
 
 The gradual sinking of the water surface of this sea is, to-day, plainly 
 visible on the high hanks on both sides, and also the subsequent under- 
 mining of the latter by the wildly meandering Khine, and then, in con- 
 sequence of its improvement, begun in 1817, between Basle and ZNIaii- 
 heim, by straightening and shortening its length from about 165 miles 
 to 11 1 miles, a deepening of the obstructed river bed and sinking of the 
 water surface of from 3 feet 3f inches to 1 feet HvV inches took place 
 in some stretches of the river. The excellent hydraulic engineer, Gre- 
 benau. observing these visible facts, was Led to the erroneous conclusion 
 that this deepening of the river bed and sinking of the water surface 
 were the result alone of the power of erosion of the Rhine, and, as he 
 at the same time found that at 07 stations on 12 rivers, during a long 
 period, there had been observed a considerable decrease in height of the 
 low, medium, and high-water stages, Grebenau advanced the incorrect 
 theory that, since the existence of all creeks, rivers, and streams, with- 
 out exception, their beds had been continually deepened, and their 
 water surfaces sunk by the power of erosion of the running water, and 
 that this erosion will continue steadily in the future. 
 
 In saying the preceding I do not wish to cast any reflection upon the 
 memory of my departed, highly valued, and personal friend Grebenau, 
 who was known and respected in the whole of Germany as a distinguished 
 hydraulic engineer, but I simply desire to clear up a very important 
 hydraulic question. 
 
 Now I will attempt to clear up, i. e., to rebut, the arguments, objec- 
 tions, and doubts heretofore enumerated of my other opponents, and 
 for that purpose will refer to the data and observations collected by me 
 since 1S73, and which strengthen the correctness of my theory and prove 
 Grebenau's utterly untenable. 
 
 J\e})1y to A. — If the decrease in height of the stages of a stream, i. e., 
 the sinking of its water surface which was observed during a long 
 period, were alone the result of the deepening of its bed, either by the 
 power of erosion of the running water or by the executed improvement 
 of the stream, these deepening* must take place in a large part of the 
 stream, must be created successively and in equal degree, and finally 
 must be permanent. 
 
 The changes in the bottom of the bed of a river, such as partial washing 
 out by whirlpools and shifting of the channel, which occur at almost 
 every high stage cannot be considered as being a deepening of the river 
 bed in the sense in which it has been herein discussed, as these are 
 generally corrected again by the next high water, and consequently 
 can have no effect upon the monthly or yearly average of the guage 
 readings. 
 
 In order to judge clearly and in a reliable manner of the effect which 
 the deepening of the bed of a stream through a long stretch has upon 
 the water stages thereof, it is necessary to plot the original cross- sect ion 
 of this stream, together with the deepening in the bed and various 
 
22 
 
 stages thereof, and we shall then arrive at the following unassailable 
 conclusions: 
 
 In the above figure let A, B, C, D represent the whole cross-section 
 and profile of discharge of a stream, which for the sake of simplicity we 
 can assume as perfectly regular and with sloping banks. In this sec- 
 tion let the line a d, ef, and g i represent respectively the low medium 
 and high stages of water. 
 
 If, then, after a lapse of a long period of time, say from twenty to 
 thirty years, the bottom of the original bed B C has been deepened to 
 the new bottom B C, either in consequence of the power of erosion or the 
 improvement of the stream, we can calculate the resulting amount which 
 the surface of the water has sunk, provided we assume that the volume 
 of water has remained the same. 
 
 Denoting the width B C of the bottom of the bed of the stream by 
 b, the velocity of discharge by v, and the distance which the bed has 
 sunk by h, the amount of discharge, m, through the deepened portion 
 of the bed B B, C C. we will have 
 
 m = b h v. 
 
 Now, denoting the width of the water surface at low, medium, and high 
 stages respectively by &, 6 2 , and 6 3 , the mean velocity at the surface at 
 these stages respectively by v, r 2 , and v 3 , and the sinking produced by 
 the deepening of the bed respectively by //, h 2 , and h 3 , it follows that 
 since the volume of water is only reduced by the amount which flows 
 through the deepened portion B B, C C, the following equations are 
 tr.ue, viz: 
 
 m = b h r=b It v = b 2 li 2 v 2 = b 3 h 3 v 3 . 
 
 Now, since in the cross-section of all streams, excepting in the rare 
 case where both banks are reveted with vertical walls, the width of the 
 water surface increases with the height of the stage, that is, b 2 > b and 
 b 3 > b 2 , and since, as is well known to every hydraulic engineer, the 
 surface velocities increase with the height, that is, that v 2 > v, and v 3 > 
 r 2 , it follows that the amount of the sinking of the water surface at 
 higher stages must be in the inverse ratio of the product b 2 r 2 to b v and 
 b 3 r 3 to b 2 v 2 , and must therefore become smaller and smaller as. the river 
 rises, that is, h 2 <; h and h 3 < h 2 . 
 
 It is evident from the above that the following criteria must be true 
 in regard to decreases in the height of the water stages, i. e., in the sink- 
 ings of the water surface which result from a permanent deepening of 
 the river bed. 
 
 1. The decrease in the height of the water must be greatest in low stages, 
 
23 
 
 and must be proportionately less in higher stages, and must reach its 
 minimum in floods. 
 
 2. Tlic decrease in the height of the water which results from the 
 deepening of the river bed must be the .same, for the same average 
 monthly stage, because this deepening only takes place slowly and 
 gradually during a long period of years, and the stream may therefore 
 be considered as unchanged during the period of a year. 
 
 3. If the gauge readings of a long river, taken in the same period of 
 time, are compared, the amount of sinking of the surface, due to works 
 of improvement or deepening of the bed, will never be the same at the 
 different stations, but on the contrary vary greatly from each other, be- 
 cause on a long river only some especially bad stretches are improved 
 gradually ami in different periods of time, and because many stretches 
 which are in a better condition, and especially those inclosed in rocky 
 banks, are left unchanged, and because it frequently happens that the 
 various stretches are improved according to different systems, which as 
 the nature of the evil varies may have quite different effects upon the 
 stream ; and finally, because in the lower unimproved portion of the 
 river, bars, sand banks, and raising of the bed occur, and therefore it 
 happens that an equal amount of the deepening of the bed and sinking 
 of the water surface resulting therefrom throughout the whole river is 
 impossible. 
 
 1. When a river is radically improved, and particularly when it is 
 considerably shortened by means of cut-offs, its bed will not only be 
 deepened, but its slope ami the velocity of its current will be increased, 
 and as a result of this its water surface will be lowered, and sometimes 
 even more than by deepening its bed. 
 
 But these sinkings of the water surface must possess these criteria: 
 that they are equal at the same station, during the same months, at the 
 same stages, independent of the years, and that even in the same im- 
 proved portions of a long river they will vary with the extent and man- 
 ner of the improvement; and finally, that a sinking in the water .surface 
 cannot take place on those portions of the river near its head or mouth 
 which are not affected by the works of improvement. 
 
 in order to furnish the proof that the considerable decrease in the 
 heights of the stages of European rivers, i. e., the sinking of their water 
 surface, as shown by me as well as by Grebenau, director of hydraulic 
 works, to exist, did not result in consequence of the power of erosion of 
 the water nor from the partial improvements made of these rivers at 
 different periods of time, but is solely due to a decrease in their dis- 
 charge. I procured authentic gauge readings at numerous stations on 
 the Khine, Danube, and Elbe, divided them into two equal periods of 
 observation, calculated for each the monthly and annual mean stage, 
 as well as the highest and lowest stages which occurred, and plotted 
 them on sheets 1 to 0, in order that they might be more readily seen and 
 compared. These sheets clearly exhibit the observations taken during 
 alongpeiiod of years, and from them the following conclusions can 
 justly be drawn, viz: 
 
 (a.) The decrease in the height of water stages, i. e., sinking of the water 
 surface of the Rhine and Elite, is indirect opposition to the criterion 
 laid down in my preceding reply to A under the head of 1 ; that is, it is 
 the least at low and increases considerably at medium and high stages, 
 and can, therefore, not be the result of a deepening of their beds. 
 
 The decrease shown at the six stations on the Danube did not agree 
 with the above, because, as will hereafter be shown, the stations at Dil- 
 
24 
 
 lingen, Linz, Vienna, and Pesth were changed during the period of 
 observation. 
 
 (b.) The decrease in the height of water stages at the same stations, 
 at the same stages of the river and during the same months varies con- 
 siderably, and the amount thereof depends far more upon the season of 
 the year than upon the mean stage of the rivers, and this observed re- 
 sult further proves that the sinking is not due either to the deepening 
 of their beds or to their works of improvement. 
 
 (c.) It will be further seen from these plottings that at several stations 
 on the same river, even when they are separated by great distances, 
 non-improved portions and stretches flowing over rock, the decreases in 
 the height of the water surface, for the separate months, are the same 
 or very nearly so, which does not agree with the criteria laid down in 
 Nos. 3 and 4 of my reply to A. 
 
 RESULTS OF SPECIAL OBSERVATIONS ON THE RHINE. 
 
 It will be seen from the plotted gauge readings at the six stations on 
 the Upper, Middle, and Lower Rhine, that the decrease in the height of 
 the water surface is the greatest in the summer months of June, July, 
 and August, and least in the winter months of November, December, 
 and January, although the high water of summer which is poured down 
 by the melting of Alpine glaciers and snow has already reached a me- 
 dium stage when it arrives at Cologne and Emmerich; and, on the con- 
 trary, the winter low w r ater of the Upper Ehine becomes high water at 
 Emmerich by the addition of the water from its tributaries ; conse- 
 quently the Rhine completely changes its nature and regimen in this 
 distance of 422J miles. 
 
 Mr. Von Salis, Helvetic chief inspector of public works, established 
 the fact that the bed of the Rhine at Basle has not deepened during the 
 relatively short period of observation from 1857 to 1S72, in a communi- 
 cation to the Imperial Academy of Sciences at Vienna, dated April 17, 
 1875, from which the following is an abstract, viz : 
 
 " Gauge readings have been taken at Basle since 1808, which may be 
 of value in discussing the question of decrease in the volume of water 
 since the station has been fixed, and the geological condition of the 
 river bed precludes the assumption of any deepening and in general of 
 any change therein." 
 
 Mr. Honsell, member of the board of public works of the Grand 
 Duchy of Baden, who is in charge of the works in the district beginning 
 at Constance and ending at the Hessian frontier, in his letter to me 
 dated November 30, 1877, has furnished overwhelming proof that there 
 has been no deepening of the bed of the Rhine either at Basle or Wald- 
 shut, by pointing out the great firmness of its bed, w T hich is composed 
 largely of rock, and the relative level of the old bridge across the 
 Rhine, built about the year 1225, and the streets of Basle. He con- 
 cludes his letter as follows, viz : 
 
 "The assertion made by Grebenau that the bed of the Rhine is sink- 
 ing or deepening must, therefore, so far as the neighborhoods of Basle 
 and Waldshut are concerned, not only be described as improbable, but 
 absolutely impossible." 
 
 It is certain also that there has been no deepening of the very rocky 
 bed of the Rhine in the mountain gorge near Bingen during the short 
 period from 1857 to 1872. 
 
 Now, if the Rhine at the four other stations shows, in the separate 
 months during the half period of observations between 1857 and 1872 ? 
 
25 
 
 a decrease in the heights of its wafer surface similar to those at Basle 
 and Bingen, it is perfectly justifiable to conclude that neither the par- 
 tial improvement of the river nor a general deepening of its river bed, 
 but another cause which operates uniformly throughout its whole length, 
 has produced the decrease in the heights of the water surface at the 
 medium stages, and ir is apparent that this cause can only be the de- 
 crease- in the discharge, which varies from month To month according 
 to the amount of the rainfall. 
 
 In 1817 the Royal Prussian Government ordered that the most im- 
 portant gauge stations on the Rhine at Cologne and Emmerich be 
 improved, and that their zero be placed 2 feet and .02 inch below the 
 lowest water known at that time, and this was done. In his admirable 
 hydraulic work, Dr. II. Berghaus publishes tables of the gauge read- 
 ings at Emmerich from 1770 to 1835, and expressly remarks that he 
 reduced the readings from 1770 to 1817 to the new zero of 1817, whose 
 height above the sea he places at 31 feet 3.11 inches. 
 
 Mf. K luge, .royal Prussian inspector of hydraulic works, at my request, 
 kindly furnished me with his official readings of the gauge at Emmer- 
 ich from 1827 to 1873, and I was thus enabled, by comparing the tables 
 between 1827 to 1835, which were before me in duplicate, to substan- 
 tiate the fact that the zero of the gauge had remained undisturbed 
 since 1817. 
 
 Since the comparison of the accurate readings of the very important 
 gauge at Emmerich during a period of 101 years, i. e.,from 1770 to 1873, 
 is very interesting and quite sufficient to decide the question of the 
 decrease of the volume of water in the Rhine, I have plotted them on 
 Sheet 2, in order that they may be better comprehended. 
 
 Now, if the period from 1770 to 1835 be divided into two periods of 33 
 years each, and the other 38 years be considered as another period, and 
 the relative gauge readings in these three periods be compared, the fol- 
 lowing noteworthy phenomena will appear: 
 
 During the period from 1770 to 1820 the variations in height of the 
 annual high and low water, as well as mean stages, were very slight, ex- 
 cepting in the case of a few year, . From 1820 to 1873 it will be noticed 
 that there were very frequent and considerable rises and falls iu the 
 high, low, and mean stages, and more frequent changes between years 
 of abundant and small water supply. 
 
 The flood of ISO I rose 0.15 inches above those of 1790 and 1S00, and 
 the low water of 1805, 1800, and 1870 fell from 3 feet 7.3 inches to 1 feet 
 0.12 inches lower than the lowest of the first period, that of 1802; conse- 
 quently the difference between the highest and lowest stages in the latter 
 period has increased 1 feet 0.0 inches. 
 
 In the last period of 38 years, from 1830 to 1873, the arithmetical mean 
 heights of the water stages decreased in comparison with those of the 
 period from 1770 to 1802 as follows, viz : 
 
 The monthly stages from 10.63 inches to 4 feet 4.. r >5 inches. 
 
 The annual stages 2 feet 4.4 inches. 
 
 The highest stages 11.46 inches. 
 
 The lowest stages 2 feet 2.2 inches. 
 
 The observations just mentioned furnish perfectly explicit additional 
 proof that in the last decades the Rhine at Emmerich has undergone a 
 considerable change in its character and regimen, and from which we 
 may conclude that there has been a change in the rainfall in the whole 
 region of its headwaters. Furthermore, since there have been no exten- 
 sive and radical improvements of the Rhine by cut-offs at Emmerich 
 since 1802, the foregoing considerable decrease in the stages of the river,. 
 
26 
 
 i. e., the sinking of its water surface at all stages and seasons, can only 
 be explained by the circumstances that its discharge must have decreased 
 considerably. 
 
 The reason why the decrease in the height of water surface proves to 
 be greater at Emmerich than ot the five upper stations is that the de- 
 crease of the volume of water in the whole upper river valley, and in all 
 the springs, creeks, and rivers which emanate therefrom, are all con- 
 centrated there. 
 
 RESULTS OF SPECIAL OBSERVATIONS ON THE ELBE. 
 
 It will be found, from the plotted readings on Sheet 3 of the gauges 
 on the Elbe at Dresden, Kiesa, and Magdeburg, from 1S37 to 1872, and 
 those on Sheet 4, taken at Dresden during a period of 68 years, from 
 1806 to 1873, that almost the same circumstances exist relative to the 
 decrease in the height of its water surface and increase in its variations 
 as have been described in the foregoing paragraph on the Rhine, and, 
 therefore, I will not discuss them here again. 
 
 A more comprehensive view of the decrease of water in the Elbe can 
 be obtained from the plotted readings of the gauge at Magdeburg, taken 
 during a period of 142 years, from 1728 to 1869, which are given in my 
 first treatise of 1873. The data described in detail in the latter, and 
 which were collected by the intern atioual technical commissions for mak- 
 ing examinations of the Elbe in 1842, 1857, and I860, are not only very 
 interesting, but fully sufficient to enable a conclusion on the question 
 before us, relating to the decrease in height of stages in that river and 
 sinking of its water surface, to be reached. They establish the fact that 
 the low- water of September, 1842, was from 3.9 to 11.4 inches lower than 
 those marked on the rocks in the river beds at Tetschen, Pirna, and 
 Strehla for the years 1616, 1706, 1719, 1746, 1782, 1790, 1800, 1811, and 
 1835, and it was, therefore, the lowest during a period of 226 years. 
 
 It will be seen from the readings collected by the subsequent com- 
 missions for making examinations of the Elbe, and which I have tabu- 
 lated on Sheet 3 for all of its stations to the head of tide water at 
 Blekede, that in 1852, 1857, 1869, and 1873 the low water of its upper 
 portion, which is thoroughly improved to Dresden and Wittenberg, by 
 means of training walls, fell about 10 inches below that of 1842, and 
 that, on the contrary, in the lower river, which is only improved in 
 stretches by quay walls, the bed was raised by sand banks and the low- 
 water stage raised. 
 
 Mr. M. W. Schmidt, royal Saxon director of hydraulic works, published 
 in the "Civil Engineer," in Kos. 4, 5, and 7 of volume 24, valuable 
 information in reference to the slope and gauge readings of the Elbe, in 
 the kingdom of Saxony, and this expert expressed the opinion, based 
 upon accurate hydraulic data, that during the last decades the mean 
 monthly and annual, and particularly these low-water stages of the 
 Elbe, in summer and fall, have decreased considerably, and to the" extent 
 of 2 feet 0.4 inch at the station at Dresden, and from 1 foot 3| inches 
 to 1 foot 6.1 inches at Riesa.* 
 
 Mr. Schmidt further proves that in consequence of the improvements 
 which were made on the river, a deepening of its bed and sinking of its 
 water surface took place, which amounted to 1 foot 2£ inches at Dresden 
 and to 7^- inches at Riesa. Since the actual decrease in the height of 
 
 * The gauge stations at Meissen are not mentioned here, because the period of obser- 
 vation has been too short, and the effect of the improvements of the river made at 
 that point has not yet been determined. 
 
27 
 
 water surface has become loj inches greater al Dresden, and from 
 7,\. to KM inches at Riesa, it is the opinion of Mr. Schmidt, "in view 
 of the strange phenomenon, that some other cause not resulting 
 from the works of improvement, must have been in operation to pro- 
 duce this sinking in the mean stages of the water, and which, taking 
 all the surrounding circumstances into consideration, can onl\ be that 
 the volume of water in the Elbe has diminished during the last twenty 
 years. Attention may be called to the tact that after the most thorough 
 researches of the imperial royal counsellor Wex on other European 
 rivers, he announced in is;:; the same conclusions which have been 
 arrived at by the observations of the height of the water in the Elbe." 
 
 Mr. Maass, of Magdeburg, member of the royal Prussian board of 
 public works, who has made the most thorough study of the circum- 
 stances connected with the height of the water and drifting of the ice 
 of the Elbe, and has published the result thereof, also gives, in his letter 
 to me dated January .'SI, 1878, it as his opinion that the decrease in the 
 height, /'. e., the sinking of the water surface of the Elbe, is due partially 
 to its improvement and partially to the decrease in its volume of water 
 which has taken place 
 
 Engineer Orbata, in "Stummer's Engineer," of 1875, ascribes as a 
 reason tor the decrease of the volume of water in the Elbe, which has 
 been universally observed, not only the clearing of the forests, but also 
 the total drainage of ponds. Emperor Charles IV ordered the con- 
 struction of ponds in the kingdom of Bohemia at the public expense, 
 and at the end of the sixteenth century the total area of these amounted 
 to oto.l square miles, of which it is said only about to the extent of 58 
 square miles now exist. 
 
 RESULTS ()F SPECIAL OBSERVATIONS OX THE DANUBE. 
 
 In making the comparison between the mean of the monthly and 
 annual readings at the most important stations on the Danube, which 
 are plotted on Sheet 5, I could not choose periods of observation of equal 
 lengths, because unfortunately some are quite short, and because the 
 cross section and the discharge of the Danube have materially changed 
 at several stations during the last decades. Correct conclusions from 
 the comparison of the mean-water stages can. therefore, only he drawn 
 by considering them in connection with the changes that have taken 
 place in the cross-section of the river. I have therefore obtained the 
 oldest as well as the latest cross-sections as determined by experts in 
 the public service at the four stations at Linz, Stein, Pesth, and Old 
 Orsova, have accurately plotted them on Sheet <'», and will now briefly 
 discuss the results of the comparison of the gauge readings at the sepa- 
 rate stations; at the same time, take the changes in the cross-section of 
 discharge into consideration. 
 
 The Danube at Dillingen. 
 
 Mr. Bernhard V. Herrmann, of Munich, chief director of the royal 
 Bavarian board of public works, in a letter to me dated December 3, 
 1877, was so kind as to communicate to me that in his opinion the quite 
 considerable decrease in the height of all stages, i. e., in the sinking of 
 the water surface of the Danube, at Dillingen. in Bavaria, which was 
 observed during the second half of the period comprised between 1835 
 and 1874, is due to the improvement of the Danube, which has been 
 energetically prosecuted during the last decades. 
 
28 
 
 The plot of the gauge readings at Dillingen is worthy of notice, inas- 
 much as the following conclusions can be drawn therefrom, viz: 
 
 The slight variations between the monthly mean, as well as the small 
 increase in height of high-water and slight decrease in height of low- 
 water stages, indicate that large tracts of forests still exist in the region 
 of the headwaters of the Danube, and regulate the flow of its water at 
 Dillingen. 
 
 The fact that the variations in the monthly mean as well as in high 
 and low water stages are so uniform, observed during the second half 
 of the period included between 1855 and 1874, proves that the extensive 
 river improvement at Dillingen has not only deepened its bed, tut has 
 also increased the velocity of its current considerably. 
 
 The plot of the gauge readings at Dillingen may therefore be con- 
 sidered as a prototype of the relative water stages of such rivers whose 
 discharges are regulated by large forests existing in their valleys, and 
 also for such as have been extensively and radically improved, and par- 
 ticularly of those in which the slope has been increased by diminishing 
 their lengths by cut-offs. Now, as none of my plots of the gauge read- 
 ings on many other streams and at various stations resemble this proto- 
 type at Dillingen. as far as regards the very uniform stages of water 
 and their nearly equal variation at all seasons of the year, it follows 
 that the causes which are at work at Dillingen either do not exist at all 
 at the other stations and on the- other rivers, or exist in only a very 
 slight degree. 
 
 The Danube at Linz. 
 
 The plot of the gauge readings at Linz, taken during the second half 
 of the period included between 1849 and 1875, shows scarcely any vari- 
 ation in the months of April, May, June, July, and August, which are 
 the five richest in water supply; but, on the contrary, during the other 
 seven months, shows a decrease in the height of water stages or sinking 
 of the water surface of from 1.42 to 8.32 inches, of 4.8 inches in the annual 
 mean, of 7.22 inches in high and 0.5 inch in low stages of the river. 
 
 It will be seen, however, from the cross-sections of the river, accurately 
 taken in 1830 aud 1877, only 54 feet 8 inches above the gauge at the 
 bridge, and which are plotted on Sheet 6, that the cross- section of dis- 
 charge was diminished by the construction of terraces and revetment 
 of the river banks about 452 at the zero, about 646 at the medium, and 
 about 1,604 square feet at the 19-foot 8-iuch stage; and that in conse- 
 quence of this decreased cross-section the surface of the water during 
 the period included between 1850 and 1875 must have been raised as 
 follows, viz : At the zero stage, about 6.66 inches ; at the medium stage, 
 about 9.84 inches ; and at the high stage, about 1 foot 10.41 inches. 
 
 If, therefore, the cross-section of discharge had not been diminished, 
 the sinking in the water surface of the river during the second half of 
 the period included between 1849 and 1875 would have amounted as 
 follows, viz : At the zero stage, to about 7.8 inches ; at the medium stage, 
 to about 1 foot 1.12 inches; and at the high stage, to about 2 feet 4.44 
 inches. 
 
 This can only be the result of a decrease in the discharge of the Dan- 
 ube at Linz, since it has not been improved at that point, and there has 
 been no deepening of its bed. 
 
 The Danube at Stein. 
 
 The gauge readings of the Danube at the city of Stein, near Krems, 
 are of the highest importance in this discussion, because at that pla:e 
 
2!) 
 
 one of the oldesl wooden pile bridges spans the Danube, and there is a 
 wharf which is very much usr<\. In consequence of the frequent re- 
 newal of the piles of this bridge, and the examinations made to deter 
 mine the besl location for its draw, frequent accurate cross-sections of the 
 river were taken, ami the gauge readings since L829 were also preserved. 
 I found, in prosecutiug my researches, that no improvement of the Dan- 
 ube w;ts male after L329 until 1*71, when its bed was narrowed at the 
 bridge; and, therefore, I have considered neither the alterations in the 
 water stajes nor changes in the bed of the river caused thereby since 
 1 ST 1. 
 
 I a'si. obtained the official cross-sections of the stream taken at the 
 bridge at Stein in L83S, 1848, 1858, L869, and 1872, compared them, and 
 finally plotted the first and last ones together on Sheet 6. From these 
 it will be seen that the bottom of the river-bed,* which is here composed 
 Of gravel, was, it is true, at times deepened by high waters, but Then 
 again filled up by them, so that the mean depth of the cross- section 
 taken in LS72 difters only .2 of an inch from that of the one taken in 
 L838. It follows from this that a general sinking of the bottom of the 
 riverbed was not effected by the power of erosion of the running water, 
 and that, therefore, Grebenau's theory seems unfounded. 
 
 Now, it will be perceived by examining the plotted gauge readings at 
 Stein on Sheet 5, that in the second half of the period included between 
 1853 and 1873, the heights of all stages of the river have decreased, as 
 follows : 
 
 The mean stages by from 3.08 inches to 1 foot 4.58 inches; the annual 
 mean stages by 8.58 inches : the mean high stages by 1 foot 10.70 inches ; 
 the mean low stages by 8.47 inches. 
 
 Now, as the Danube was not improved at Stein, nor any deepening in 
 the bottom of its bed took place, the assertion that this decrease iu its 
 water stages is alone due to the decrease in its discharge can be made 
 with the fullest justification. 
 
 The Danube at Vienna. 
 
 The changes which have taken place in the cross-section of discharge 
 of the Danube at Vienna could not be determined, because if was di- 
 vided at this place into two large arms and the Vienna Danube Canal, 
 which is 54 yards and 2 feet wide, ami because a number of smaller sub- 
 sidiary channels which existed just below the city were closed. It can, 
 however, be generally asserted that the cross-section of discharge de- 
 creased considerably during the period included between 185] to 1874, 
 by reason of the faci that the southern arm, the so-called "Kaiserwas 
 ser,"t 162 yards wide, which formerly was <! feet 6| inches deeper than 
 the zero, and which had a considerable discharge, is so filled up that 
 now. at the zero stag.-, there is none, while at the same time the cross- 
 section of discharge of the northern arm has changed but little. 
 
 lt\ notwithstanding this, the tabulated comparison of the water stages 
 and the plot thereof on Sheets show that the monthly and annual 
 mean as well as the high and low water stages for the period included 
 between 1851 to 1874 have decreased from 5.1 inches to 1 foot 8.9 inches, 
 
 * The original supposition of the government experts, thata portion of the river-bed 
 was rocky, was subsequently proven to be incorrect by the deepening which took 
 Place; ami tin- rooky ledge, which shows itself in tin-' river-bed about 1,968 yards 
 below, either does not reach up to the bridge, or, if it does, lies at a great depth. 
 
 t Imperial stream. 
 
30 
 
 as they do, it follows that the discharge of the Danube has decreased 
 during that period. 
 
 The gauge readings since 1874 are not considered in this .discussion, 
 because the cut-off at Vienna, which has the normal breadth and depth 
 of the stream and a length of 4 miles and 13 yards, was opened in 1875, 
 the old channel completely closed, and the gauge station transferred to 
 the cut-off, and therefore no reliable conclusions could be drawn by com- 
 paring the readings before and after the opening of the cut-off. 
 
 The Danube at Old Orsova. 
 
 The gauge readings of the Danube at the city of Old Orsova are 
 very important and very satisfactory in the discussion and decision of 
 this question of the decrease in the volume of water, because all the 
 larger tributaries empty into the stream above this plaee, and, being in 
 consequence thereof a mighty stream, replete with water, the abnormal 
 stages of water in single tributaries, caused by particular elementary ac- 
 tions in their valleys, have no influence on its discharge at Orsova. 
 
 Again, in consequence of the great difference in the configuration, 
 composition of the soil, and climatic conditions of the several valleys 
 of the tributaries which flow into it from the south, west, and north, 
 these carry off their high and low water, at different times, the Danube 
 at Orsova may be considered as a. great recipient and regulator of the 
 high, medium, and low waters of its tributaries. 
 
 For these reasons, the most reliable conclusions relative to the dis- 
 charge of the stream produced by the water which it receives from its 
 whole upper valley can be drawn from the gauge readings at this sta- 
 tion, but only then if it is proven that during the period in which the 
 readings were taken there has been no change in the direction of its 
 current, its cross-section of discharge, or in its slopes. 
 
 it can be seen from any large river map of Europe, and from works 
 published on hydraulic subjects, that the bed of the Danube for a dis- 
 tance of G5.8G miles below Orsova is situated in a vast mountain gorge 
 of the southern chain of the Carpathian ranges, and that throughout 
 this whole distance its sides, and throughout most of it its bottom, con- 
 sists of rock, from which it may safely be inferred that the direction of 
 its current and its cross-section have remained unchanged during cen- 
 turies. 
 
 It will further be seen from the plan and cross-sections made by the 
 very intelligent Hungarian hydraulic engineer, Paul Vasarhelyi, between 
 1S32 and 1834, which I published, to gether with a lecture entitled 
 ' Ueberdie SchiffbarmachungderDonau am Eisernen Thore und an den 
 sieben Felsenbanken oberhalb Orsova, 1 '* in the " Zeitschrift des oster- 
 reichischen Ingenieur und Arcaitekten Vereins,"t in ]STo. 10 of 1872, that 
 at a point 981.85 yards above Orsova the Danube had a nominal width 
 at the zero stage of 462} yards and a depth of 38 feet loi inches in the 
 center of its channel. 
 
 Xow, since Sir John Wawra, imperial and royal director in chief of 
 the board of public works, who was sent to Orsova as a member of the 
 international commission of experts to devise ydans for the improve- 
 ment of the Danube, took its cross- section in 1873 in the most careful man- 
 ner, which cross-section is plotted on Sheet 6, and found that the river, 
 at a point 961.85 yards above Orsova, was 463£ yards wide and 38 feet 
 
 * On making the Danube navigable at the Iron Gate and at the Beven rocky ledges 
 above Orsova. 
 t Journal of the Society of Austrian Engineers and Architects. 
 
•' 1 
 
 .v inches deep in the center of its channel, the proof is furnished b\ 
 the approximate coincidenc • of these measurements that at Orsova the 
 bed of the river, its depth,, am I its cross-section of discharge have re- 
 mained unchanged since 1832, which is quite natural, since its cross-sec 
 tions art' bounded by rocks, both above ami below that city, and make 
 a change therein impossible. 
 
 Although it is true that the firsl private "Danube Steam Navigation 
 Company" between 1S47-1S4 , .», ami subsequently in 1855, the imperial 
 royal Austrian Government did remove, by blasting, some projecting 
 rocks which endangered navigation at the lower end of the tails at the 
 Iron Gate, yet these could not have the least influence upon the stages 
 o" the river at Ursova, because the sections of the removed rocks were 
 i isignitioant compared to the cross section of the river, and because they 
 were a part of a ledge which is situated 5.0 miles below that city at the 
 foot of the falls, consequently below its crest, and whose surface is 
 about i'."> feet below the zero of the gauge at Orsova. 
 
 Now. as it can be seen from the profile of the river, which I published 
 in 187l\ that, between Orsova ami the Iron Gate and at the distances 
 of 2.8 and 4.04 miles, two continuous ledges of rock, whose upper sur- 
 faces lie only 4 feet 4 inches and 4 feet 8 inches below zero, stretch em 
 tirely across the riverbed, it follows further that it would be a down- 
 right impossibility for the slope of the Danube to have changed at that 
 point, and it can therefore be safely asserted that, during the period from 
 1840 to L875, in which the gauge readings were taken, the direction of 
 the current, moss section, and slope of the 1 >anube remained unchanged 
 at ( trsova. 
 
 A comparison of the tabulated readings of this gauge, taken during 
 the second half of the period of observation between 1858 and 1875, and 
 the plot thereof, as presented on Sheet .">. will show that the mean of the 
 monthly and annual as well as the high and low water stage has de- 
 creased from 6.18 feet to 2 feet 5 inches, and this general decrease in the 
 volume of water, i. c, in the height of its water surface at Orsova, can 
 o ily be accounted for by the fact that the discharge of the stream has 
 d in hushed there. 
 
 It is notorious that, during the last decades, in several of the tribu- 
 te ies of the Danube — as, for instance, theTheiss and the Save — the Hoods 
 S aietimes rise higher than they formerly did, and their discharge is 
 thereby increased, and that their floods are frequently poured into the 
 great bed of the Danube and pass Orsova simultaneously with the water 
 from other tributaries which are at a medium or low stage, vet the gauge 
 r adings. taken during the second half of the period of observation, show 
 that these accumulated waters no longer reach the same height which 
 they formerly did. and that the heights of the greatest floods are not as 
 gieat as they formerly were by 1 foot 9.65 inches. The facts thus fur- 
 nished by the huge masses of water, collected together by nature itself 
 in the Danube at Orsova, certainly will furnish every one with clear and 
 indisputable proof that the high Hoods which sometimes occur in sev- 
 eral of the tributaries do not compensate for the continued decrease in 
 the discharge of the others at their low and medium stages. 
 
 By comparing the readings of the six gauges on the Danube it will be 
 seen that at Stein, Vienna, and Orsova the decrease in the height of the 
 water stages is greatest during the month of October; consequently, a 
 uniform cause throughout the whole valley must have operated to pro- 
 duce the uniform effect, and that cause must have been a decrease in 
 the rainfall. 
 
 It will also be seen by this comparison that the regimen of the Dan- 
 
32 
 
 ube is partially changed in its course from Linz to Orsova, as the great- 
 est discharges at Linz, Stein, and Vienna take place during the months 
 of June, July, and August, i. e., during the period when the snow on 
 the Alps melts, and on the contrary at Orsova during the months of 
 April and May, i. e., during the rainy season of spring. 
 
 Although the foregoing proof, furnished by the decrease in the dis- 
 charge throughout the whole length of the three principal rivers of 
 Central Europe, i. e., the Danube, Ehine, and Elbe, of the correctness 
 of my theory in regard to the decrease in the volume of water in springs 
 and rivers would seem to suffice, I have, nevertheless, in the interest of 
 science and for the purpose of inciting the arrangement and publication 
 of further observations pertinent to this subject, and finally, in order to 
 make the thorough study of this highly important hydraulic question 
 by my fellow professionals and naturalists more easy, at the end of this 
 treatise added a tabular exhibit compiled from the gauge readings col- 
 lected by me anil Mr. Grebenau at 51 stations on 13 rivers. These 
 readings were divided into periods, -and from these the annual mean 
 height of the water stage, as well as of the high and low stages, were 
 calculated, and finally from these ascertained the decrease in the read- 
 ings during the second half of the period of observation, in order that 
 the latter at separate stations and rivers could be more easily compared 
 with each other. 
 
 I take the liberty of giving the following explanation of the manner 
 in which the calculations for this exhibit were made. I not only calcu- 
 lated the monthly mean stages because a comparison of the latter shows 
 not only the changes which took place in the regimen of the rivers, but 
 also clearly the fact that the decrease in the height of their water sur- 
 faces could not be alone explained by a deepening of their beds. 
 
 In this tabular exhibit of gauge readings I took the mean of the vari- 
 ous high and low water stages which occurred in each year, but even 
 these do not furnish so clear and instructive a picture of the relative 
 discharge of a river during long periods as the plots of its lowest, medium, 
 and highest stages which I presented in my first treatise for the Ehine, 
 Danube, Elbe, Vistula, and Oder, and in this on Sheets 2 and 4 for the 
 Ehine at Emmerich and the Elbe at Dresden. By an examination of 
 the annexed tabular exhibit and the calculated means of the gauge 
 readings at 51 stations on 13 rivers, the following important conclusions 
 may be drawn, viz: 
 
 1. Of the 100 differences in the gauge readings which are given in the 
 table, 149 show a decrease and only 11 an increase in the height of water 
 stages, and it can easily be proven that the latter were caused either by 
 the present increase in the height of flood stages or by a decrease in 
 the cross-section of discharge or by the bottom of the bed of the stream 
 being covered with sand. 
 
 2. The average annual decrease in the height of the water surface, i. <?., 
 sinking of the water surface, is not only different on different rivers, 
 but also for the different stations on the same river, and this is also the 
 case with the low, medium, and high water stages, and evidently result 
 from a difference in the amount of the rainfall in the different parts of 
 the valleys. Xot only the decrease in the water supply caused thereby, 
 but also the deepening of the river bed resulting from works of improve- 
 ment at certain localities, and finally, also, the configuration of the cross- 
 section of discharge must have exerted a great influence in lowering the 
 water surfaces. For this reason Grebenau's attempted calculations, based 
 upon an equal mean in the decrease in the height of the water surfaces 
 for all of the 14 rivers and 75 gauge stations discussed by him, as well 
 
33 
 
 as for the different stages thereof, are entirely inadmissible, since only 
 incorrect results can be obtained from them. 
 
 .!. Since tiie closest examination of the plot of the gauge readings on 
 the live livers, Rhine, Danube, Elbe, Vistula, and Oder, presented in my 
 first, as well as in this treatise, does not reveal that in the ease of these 
 rivers the number of the years which are rich or poor in water supply 
 is not fixed in duration, or that they change regularly, or finally that 
 they return at fixed periods, it cannot be determined during how many 
 years gauge readings must be taken in order to be able to calculate 
 from them a thoroughly reliable mean, and consequently cannot be de- 
 termined, either theoretically or by experience, how long it is absolutely 
 necessary that the two periods of observation which are to be compared 
 should be. But it is clear to all that the longer the periods of gauge 
 readings are, the more correct and reliable will be the mean calculated 
 from them, since the years which are either very rich or poor in water 
 supply, and which undoubtedly occur in the one or the other of these 
 periods, have so much the less influence upon the calculated mean. 
 
 In consideration of the foregoing, the calculated decrease in gauge 
 readings given in the annexed exhibit must have a greater value than 
 such as were deduced from readings made during a shorter period. 
 
 It is also clear from this exhibit that the mean decrease in the height 
 of the water derived from readings taken during a shorter period, and 
 that the sinking of the water surfaces has become considerably greater in 
 the last decades than formerly, which is explained by the fact that iu the 
 last decades there have been a greater amount of clearing, drainage of 
 ponds and marshes, and improvement and irrigation of large tracts. 
 
 No. 
 
 Names of rivers and gauge stations. 
 
 Sinking of 
 the annual 
 mean of the 
 gauge read- 
 ings 
 
 1 
 
 Basle 
 
 I. — KlIIMC. 
 
 In inches. 
 0. 114 
 
 21 
 
 
 24 
 
 2"> 
 
 
 0.40 
 
 31 
 
 
 IT.— Danube. 
 
 0.41 
 
 32 
 
 
 425 
 
 34 
 
 ( »ld ( )rsova 
 
 0.9 
 
 35 
 
 
 III.— Elm:. 
 
 *0. 197 
 
 40 
 
 
 0.394 
 
 42 
 
 
 CV. — Vistula. 
 
 0.433 
 
 43 
 
 
 0.558 
 
 44 
 
 
 V.— Oder. 
 
 0.114 
 
 53 
 
 Tan's 
 
 X.— Seine. 
 
 tO. 59 
 
 54 
 
 
 XI. — Olommen. 
 
 0.11 
 
 55 
 
 
 0.24 
 
 56 
 
 
 XII. — Mississippi. 
 
 0.697 
 
 
 
 
 * The amount of the sinking of the water surface due to the deepening ot the bed by improvement 
 of the rivera was deducted at Vienna and Dresden. 
 
 t At Paris the mean of the decrease in gauge readings at the highest and lowest stages were taken. 
 
 3 w 
 
34 . 
 
 4. From the annexed tabular exhibit the foregoing schedule fs ob- 
 tained by considering Only the variations of the mean stages which are 
 really the most noteworthy, at the most important stations at which 
 material changes have taken place in the bed of the stream, and finally 
 those that are derived from readings made during the longest periods. 
 
 From the schedule it will be seen that the decrease in the gauge read- 
 ings increases in different rivers with the greater extent of their valleys, 
 which seems to me- to be another proof that the decrease in their dis- 
 cbarge is due to a decrease in rainfall and the consequent decrease in 
 the volume of water. 
 
 Reply to B. — The supposition of some of my opponents that it cannot 
 be reliably concluded from a decrease in the gauge readings on a river 
 that its discharge has decreased is unfounded, as the following proofs 
 will show : 
 
 Mr. Grebenau, who was known as one of the most skillful hydraulic 
 experts in the measurement of discharge of rivers ami streams in Ger- 
 many, while stationed at Germersheim in his former rank of inspector 
 of public works, measured the cross-section, the slope, and the velocity 
 of the current of the Ehine thirty-eight times at six points near ]Seu- 
 burg, Pforz, and Germersheim, and with all possible accuracy, and from 
 these he calculated the quantity of water which the Ehine had discharged 
 during the period of twenty-eight years included, between 1840 and 
 1867, which calculations I published in my first treatise of 1873. From 
 these measurements Mr. Grebenau calculated the mean discharge of the 
 Ehine, during the period from 1840 to 1867, to have been 41,596 cubic 
 feet per second, and that the reading of the gauge at Sonderheim, cor- 
 responding to this discharge, should be + 'd'o.3Q§&" . The arithmetical 
 mean of all of the readings taken at this gauge during the above period 
 was found to be + 3' 1", so that the difference between the two amounted 
 to only 2.3685". 
 
 Mr. Grebenau, in communicating the result of these measurements to 
 me in his letter dated February 2, 1872, gives the following opinion, 
 viz : 
 
 " From this it follows that the mean stage of the river nearly corre- 
 sponds to the arithmetical mean of the gauge readings, and that the 
 error would have been small if in the beginning the discharge of the 
 Ehine had been deduced from this arithmetical mean. This is a new 
 and not unimportant law, which saves great and extensive calculations." 
 
 Grebenau, in his pamphlet on the results of gauge readings on the 
 Ehine and Mosel, published in 1874, on page 20 makes the following re- 
 mark bearing upon this point : 
 
 "Although the annual mean discharge of the Ehine deduced from the 
 mean stage is nearly in the same ratio as the mean of the gauge read- 
 ings, yet it does not follow from the difference in these mean stages, which 
 was observed during the two periods, before and after 1840, that its dis- 
 charge has decreased, since the difference is solely the result of the im- 
 provement of the river." 
 
 That the mean discharge of other rivers can be nearly accurately calcu- 
 lated from the mean of the gauge readings is apparent from the follow- 
 ing results of measurements : 
 
 Mr. Harlacher, professor of the science of engineering at the German 
 Polytechnical Academy, at Prague, measured with the greatest accu- 
 racy the discharge of the Elbe at Herrnskretschen, on the boundary 
 line between Bohemia and Saxony, at the same cross-section, and at its 
 various stages, and calculatt d from these the discharge during the 
 twelve months, fioni July 1, 1871, to the end of June, 1872, and although 
 
60 
 
 during the period there were five floods (and anion-' them the extraor- 
 dinary one of -May, L872, caused by bursting of clouds), nevertheless, 
 Mr. Harlacher found that the difference between the mean of the gauge 
 readings and the height of the water surface due to the mean discharge 
 of the river, during these twelve months, amounted to only 3.15 inches, 
 and after a more accurate calculation to only 1.575 inches. (See "Beit- 
 riige zur Hydrographie Bohmens," von A. K. Harlacher, Prag, 1872 and 
 1875.*) 
 
 It should here be remarked that in both cases calculated by Grebenau 
 and Harlacher the mean of the gauge readings was smaller than the 
 height of the stage corresponding to the mean discharge; furthermore, 
 that the difference amounted to nothing in months during which only 
 moderately high waters occurred, as will be seen from Harlacher's cal- 
 culations, and on the contrary in months during which very high waters 
 occurred the difference becomes somewhat greater, but yet on an aver- 
 age, dining long periods, it will be found very small. 
 
 Now. as it may be assumed that the conditions just mentioned existed 
 in the other streams during the various periods of gauge readings, and 
 in further consideration of the fact that the height of the water stage 
 corresponding to the mean discharge can only be determined by very 
 difficult and extensive hydraulic measurements and calculations, in 
 which considerable mistakes may easily be made, every experienced hy- 
 draulic engineer will agree with me that in such stretches of streams, 
 in which the cross-section and the slope have remained unchanged, it may 
 be concluded with complete justification and reliability, from a decrease 
 in the mean of gauge readings taken during a long period, that their 
 discharge has decreased. 
 
 Reply to C. — The supposition expressed by some of my opponents — that 
 the discharge of rivers and streams has probably not decreased but that 
 only their regimen has changed, since although at present that discharge 
 at low and medium stages is smaller, yet it is very much greater at high 
 stages, and that therefore the decrease in the former cases may be com- 
 pensated by increase In the latter cases — is plainly incorrect, since on 
 several rivers and at many gauge stations thereon the readings of high 
 stages have decreased during the second period of observation. This 
 has taken place on the Rhine at Basle, Worms, Bingen, and Cologne; on 
 the Danube at Stein and Orsova; on the Vistula at Cracow; and on the 
 Oder at Iviistin. The supposition is further increased because in calcu- 
 lating the annual arithmetical mean of the gauge readings, the high- 
 water stages are included, and because the monthly and annual mean 
 of high-water stages have been found to decrease at almost all of the 
 .~»1 stations on 13 rivers, which are compared in the tabular exhibit, and 
 finally, because, if only a change in the regimen had taken place, the dis- 
 charge during some months should decrease, and in the other months in- 
 crease, a circumstance which has not taken place on any of the streams 
 which are mentioned, except at a few gauge stations. 
 
 In my description of the circumstances attending the discharge of the 
 Ehine at Emmerich and the Danube at Old Orsova I have already given 
 the most striking proof that the decrease in low and medium stages is 
 not compensated by that of the high stages which occasionally occur. 
 
 Reply to D. — The assertion made by Mr. Sasse, member of the board 
 of public works, in his treatise upon the relations of the Elbe at Torgau, f 
 
 * Contributions to the hydrography of Bohemia, by A. R. Harlacher, Prague, 1872 
 and 1875. 
 
 tZeitschrift fur Bauwesen von Erbkam. Jahrgang, 1-?!. Journal of Architecture, 
 by Erbkam, 1874. 
 
36 
 
 that no reliable conelusions can be reached that the discharge of streams 
 has decreased until gauge readings have been taken during a period of 
 at least 200 years could only be true if it were established that the years 
 which are either very rich or very poor in water supply alternate and 
 return at loug intervals of about 40 or 50 years, for then it would be 
 necessary at any rate to take at least two periods rich and two periods 
 poor in water supply in order to obtain a reliable mean. But since it is 
 apparent from the plotted gauge readings, in this as well as in my first 
 treatise, of five rivers, during periods of from 60 to 142 years, that the 
 periods rich or poor in water supply do not habitually last louger than 
 from three to five years and that they do not recur in regular order, 
 and since the further assumption of Mr. Sasse that the discharge of 
 streams during years rich is frequently three times as great as that dur- 
 ing years poor in water supply is true only of the smallest number of 
 streams andjmly very seldom, of which my plotted gauge readings will 
 convince any one, his assertion that in order to reach a reliable conclu- 
 sion as to the decrease in the discharge of rivers gauge readings must 
 be taken during a period of at least 200 years appears unfounded, since 
 from my plotted gauge readings it appears that we can — if we take these 
 during periods of from 40 to 00 years, divide them into two periods, cal- 
 culate the mean of each of these, and then compare these means — infer 
 from an increase or decrease in these that the discharge has become 
 greater or less. 
 
 I should remark, however, that if in any year in either of the half 
 periods of observation a flood, produced by extraordinary action of the 
 elements, should occur, as happens rarely during 100 years, it would cer- 
 tainly seem advisable in order to obtain a correct mean of the gauge 
 readings to exclude such an abnormal year and substitute for it the year 
 of the other half period which was richest in water supply. I did not, 
 however, deem it necessary to make the correction just referred to in 
 my exhibit and plot of the gauge readings. 
 
 Reply to E. — The opinion of some of my opponents that a decrease in 
 the discharge can only be reliably established by making direct meas- 
 urements of it on rivers and streams from time to time during long 
 periods, seems at first to be evident, but if we calmly consider the whole 
 proceeding and the manner in which such measurements and calcula- 
 tions must be made, the surprising result will be reached that to estab- 
 lish the decrease in discharge by direct measurements is quite impracti- 
 cable and almost impossible, as I now propose to show. 
 
 First of all, every hydraulic engineer will agree with me that it is an 
 utter impossibility to make during 30 or 40 years uninterrupted meas- 
 ures of discharge, and at the varying stages at such stretches of streams 
 in which the current, the cross- section, or the slope are constantly 
 changing, and then by comparing the volumes of discharge of the two 
 periods to determine whether an increase or decrease has taken place. 
 In this matter every experienced hydraulic engineer will agree with me 
 that the discharge can only be measured on those stretches of the stream 
 in which the current, cross-section, and slope have remained unchanged 
 during 30 or 40 years, as I have shown to be the case on the Ehine at 
 Basle and on the Danube at Old Orsova. 
 
 Now, if we assume that, in order to decide the question whether the 
 discharge of a stream has increased or diminished, a hydraulic engineer 
 is intrusted with measuring it on an unchanging stretch of it during a 
 period of 30 years, and assuming also, for the sake of simplicity, that in 
 this stretch only those stages occur — that is, the lowest A, the medium 
 //', and the high A 2 — and that he has in the first year executed his trust, 
 
37 
 
 and has ton ml by accurate measurements that at the selected cross-section 
 of the stream the discharge per second at the stage h was M, at the stage 
 
 h l was Ml 1 , and at the stage lr was M 2 . 
 
 Now, if the engineer, after 5, 10, 20, or 30 years have elapsed, makes 
 i similar accurate measurements of discharge at the same cross-section at 
 the same three different stages, it is evident that, if the current, cross- 
 section, and slope of the stream have remained entirely unchanged, he 
 will find exactly the same quantities of discharge, M, M 1 , and M 2 , and 
 it will l»e impossible, in spite of these measurements, after a lapse of 30 
 years, to determine whether there has been an increase or decrease in 
 the volume of discharge? since the gross amount of the latter depends 
 upon the duration of the low, medium, and high water stages. 
 
 What has just been said concerning the three stages of the water is 
 also true of all the variable stages of a stream during the whole period 
 of observation, and therefore my assertion that the volume of discharge 
 of a stream cannot be determined by measurements at an invariable 
 cross section, when the discharge will during the whole period of obser- 
 vation be the same for the same stage of water, but only from the cal- 
 culated mean of the gauge readings whether the volume of discharge 
 has increased or decreased, seems well founded. 
 
 If it is desired, however, to calculate and compare with each other the 
 gross volume of discharge which takes place during two periods of 
 about fifteen or twenty years each, the following method, already 
 adopted by Mr. Grebenau in calculating the gross volume of discharge 
 of the Rhine at Sondernheim from 1810 to 18G7, aud by Mr. Sasse, 
 member of the board of public works in his calculation of the gross 
 volume of discharge of the Elbe at Torgan * from 1831 to 1850, must be 
 pursued. 
 
 First of all the curve must be constructed based upon accurate meas- 
 urements at various stages, and at a constant cross-section, from which 
 the discharge at any stage can readily be obtained for a second of time. 
 Then from the table of gauge readings the exact number of days of the 
 period during which each stage lasted, and then multiplying the dis- 
 charge M M]M;, &c, per second at each stage by 60" x 00' x 21= 
 86,400 seconds, ami this product by the number of days of each half 
 period of fifteen or twenty years, during which the stage lasted, and add- 
 ing together all of these sums for each of the two periods, we can learn 
 from the resulting gross amounts whether in the second half of the pe- 
 riod of observation the discharge has decreased. 
 
 Now every experienced hydraulic engineer must agree with me that 
 it is very difficult to measure the discharge of a large stream at the dif- 
 ferent and especially at the high stages, also to obtain the correct curve 
 from these, and also to make the weary, time-robbing, and tiresome col- 
 lection of the same stages from the tables of gauge readings taken dur- 
 ing a long period, and to make the unavoidable rounding off of those 
 that are nearly alike to get them into designated groups, and finally to 
 perform the similar time consuming multiplication and addition of colos- 
 sal sums, in consequence of which a very busy engineer must intrust 
 the labor to an assistant, and that mistakes are very easily made which 
 may be greater than the actual difference between the gross amounts of 
 discharge of the two half periods of observation, and actually reverse 
 the result, and that on the contrary the calculation of the annual mean 
 stage of the river, as. well as the mean of the gauge readings taken dur- 
 
 "Zeitschrift fur Bauwesen von Erbkam, voai Jahr 1-374. Journal of Architecture, 
 by Erbkam, 1874. 
 
38 
 
 ing a long period of time, can be made easily and without error from the 
 tables of gauge readings. 
 
 Under these circumstances hydraulic engineers will probably now 
 acknowledge that the result of Grebenau's experience in the measure- 
 ments aud calculations of discharge so numerously made by him, that 
 the arithmetical mean for a long period, calculated from the tables of 
 gauge readings, is nearly identical with that stage of the river which 
 corresponds to the mean of the discharge obtained from measuring the 
 volume of discharge during that period, is highly important, and it is 
 therefore easier and more reliable to obtain the mean stage of a river dur- 
 ing a long period from the tables of the gauge readings taken during 
 that period. 
 
 Now I will mention another simple method by which, without the very 
 difficult and time-consuming measurements of discharge, even a non- 
 professional can calculate the amount of decrease in the discharge of a 
 stream during a certain period. It must be here remarked that only 
 such stretches and such gauge stations, where the current, cross- section, 
 and slope of the stream have remained unchanged during the whole pe- 
 riod of observation, are suitable for reliable calculations of the actual 
 decrease in discharge, and I will therefore, to illustrate my method by 
 examples, take the stations on the Rhine at Basle and on the Danube 
 at Orsova, both of which are fully suited thereto. 
 
 According to the comparison of the gauge readings in the annexed 
 tabular exhibit in No. 1, the annual mean stage of the Rhine at Basle 
 decreased on an average during the second half of the period of obser- 
 vation from 1809 to 1808 (that is, from 1839 to 1868) at the rate of .114 
 inch i>er annum; that is, an upper layer of water .L14 inch thick was 
 discharged less each year. Mr. Grebenau, it is true, did not give the 
 mean of the annual stage from 1839 to 1868, but it will probably be very 
 nearly the same as that for the period from 1840 to 1872 given in No. 2 
 as 5.8495 feet, or 5 feet 10.194 inches above zero. If now the mean sur- 
 face velocity for this stage is obtained, which can easily be done by 
 throwing a number of floats into the stream at equal distances apart, 
 we can, by multiplying the breadth of the stream by the mean surface 
 velocity and the product by the established sinking in the height of the 
 water surface, i. e., .114 inch, obtain the volume of water per second by 
 which the discharge of the Rhine at Basle is decreased. All the data 
 necessary in order to make the calculations for this case can be obtained 
 from the "Internationalen Rheinstrom-Messung bei Basel im Novem- 
 ber 1867." * It will be found from this scientific and very thorough 
 work that at the stage 5' 10.194" above the zero of the water at Basle 
 the width of the water surface is 728.31762', and the mean velocity of the 
 water on the surface of the Stream is 7.4144', so that the decrease in the 
 volume of discharge will be 728.31762' x 7.4144' .00952=46.7971 cubic 
 feet per second, and by further multiplication will amount to 1,475,794,557 
 cubic feet per annum. 
 
 Now, as the area of the whole valley of the Rhine above Basle is giveu 
 in the Swiss charts at 35,900,900,000 square meters = 386,468,017,300 
 square feet, the foregoing decrease in the discharge of the Rhine would 
 
 1 475 794 557 
 indicate a decrease in the depth of the rainfall of ,y s v> 4fL 1T47 3oo = 
 
 .0038'= .0456" per annum. 
 Now, if we base our calculations upon the decrease in the height of 
 
 * International measurements of the Rhine at Basle in November, 1867. These mea. 
 urements of the Rhine were described and published by Grebenau. March, 1873. 
 Liudauer's bookstore. 
 
water-stages during the period of Hi years from 1857 to L872, which, 
 under the head of Xo. 2 in the tabular exhibit, is shown to be .77556"= 
 .06463', and take the corresponding dimensions from the work above 
 cited, i. >., the stage at 5.3344', the width at 659', and the mean velocity at 
 6.56', the decrease of the water during the period will be found to be 
 C.V,)' x 6.56' x .06463'=279.5703 cubic feet per second and 8,816,528,981 
 cubic feet pel' annum. The amount of decrease in the depth of rainfall 
 
 8,816,528,98] 
 
 per annum would therefore be ., w> .. ,,.., ., ,^ ., n< . = .0-?L ) .S / =:.L ) <.'i(i // . 
 1 oM),4l)i5, 04 *,.>0< I 
 
 It will be shown hereafter how nearly these calculated results agree 
 with the meteorological observations. 
 
 During the second half of the period of 36 years, /. e., from 1£58 to 
 1875, the mean stage of the Danube at Old Orsova was 8.21 16' and the 
 average decrease of the latter .0748', as will be seen at No. 34 of the* 
 tabular exhibit. 
 
 According to the cross section of the Danube at Old Orsova, taken in 
 1873 by Sir Wawra, chief of the. board of public works, and shown on 
 Sheet 6, the width of the stream when at this stage was 1,549', and the 
 mean surface velocity, taken, however, at a stage only 3.28071' above 
 zero, was 2,687'. 
 
 It is universally known that the mean surface velocity of a stream 
 increases with its height, and hence I ascertained by actual measure- 
 ments of the velocity of the Danube at different stages between Ofen 
 and Pesth, and at a similar cross-section at the foot of Block's hill, that 
 when the water rises 4.02' then the mean velocity of the surface cur- 
 rent is increased about 1.148'. It can therefore be assumed approxi- 
 mately that when the Danube at Old Orsova is at its 8.2116' stage its 
 mean surface velocity will be 2.687' -4- 1.148' =3.835'. 
 
 The decrease in the discharge for an animal diminution of .0748' in 
 Ihe height of the stage would therefore be 1.549' x 3.835' x .0748' = 
 43.2189 cubic feet per second, and consequently 1,302,951,220 cubic feet 
 per annum. 
 
 The whole valley of the Danube has an area of 14,420 geographical 
 square miles, of which the portion below Orsova contains 4,100. The 
 portion above this place then contains 10,320 geographical square miles 
 =6,093,561,254,602 square feet. The decrease in rainfall is therefore 
 
 1 'U¥> QK1 '''Ml 
 
 found to be ' :v' T,' . =.000224' =.0027" per annum, and there- 
 0,093,561,254,602 
 
 fore during the whole period of 18 years, .0480 inch. It is no doubt self- 
 evident that this decrease in rainfall was greatest in the mountainous 
 regions and on the contrary less on the plains. 
 
 Reply to F. — In order to remove the doubts and exceptions in regard 
 to the correctness of the assertion made by me that the rainfall has 
 been decreased by the destruction and devastation of extensive forests, 
 I believe it to be necessary, in the first place, to call attention to the 
 opinions and treatises on this subject by distinguished experts and natu- 
 ralists given in detail in Chapter I, and then to communicate the follow- 
 ing explanations and results of my observations. 
 
 It is quite natural that the meteorological observations made in En- 
 gland, Scotland, and at Paris, St. Petersburg, and Copenhagen, during 
 about 100 to 190 years, did not indicate any decrease in the volume of 
 the annual rainfall, since these countries and cities are situated in the 
 vicinity of the sea, and receive the rain clouds, so to speak, from first 
 hands. Even if it should appear from the meteorological observations 
 at the principal cities of the continent that at these no decrease of rain- 
 fall had taken place, this can be explained by the fact that during the 
 
40 
 
 last decades no such extensive clearings as would cause a decrease in 
 the volume of rainfall have taken place in their vicinities. 
 
 I can give only two instances to prove that there has been a decrease 
 in rainfall in those regions, and especially those of a mountainous char- 
 acter, in which large clearings were made, because, unfortunately, in 
 former times no meteorological stations existed in these localities. 
 
 Mr. Adam Seidel, chief forester at Bodeubach, in the Erz* Mountains 
 of Bohemia, made precise meteorological observations uninterruptedly 
 during the period from 1828 to 1873, the results from which were revised 
 and published by the Imperial Royal Central Bureau of Meteorology. 
 If the observations of 1828 and 1850, which were incompletely made, are 
 eliminated, and then divide the remainder of the time into two equal 
 periods of 22 years each, and calculate their arithmetical means, the fol- 
 lowing results will be obtained, viz : 
 
 Meteorological- observations by Chief Forester Adam Seidel, at Bodeubach : arranged ly 
 
 Stanislaus Kostliwy. 
 
 Mean temperature of the air ' degrees Fahrenheit. 
 
 Pressure of vapor inches . 
 
 Humidity of the air per cent. 
 
 Number of days of rain 
 
 Depth of rainfall inches. 
 
 These results substantiated the fact that in the mountainous regions 
 at Bodeubach a decrease in the pressure of the vapor, relative damp- 
 ness of the air, the number of days of rain, and the depth of rainfall 
 has taken place in the latter period of 22 years. 
 
 The annual decrease in the depth of rainfall amounted to -■§-§- = 0.057 
 inch. 
 
 Mr. Plantamour, the director of the meteorological observatory at 
 Geneva, also has shown that a decrease of rainfall has taken place in 
 the Alps. He found, namely, in the latter period of 14 years, from 1S01 
 to 1874, in comparison with the preceding period of 20 years, on the St. 
 Bernard, at a height of 8,110.5 feet, an increase of temperature of 0.72° 
 F., a decrease in rainfall of .008 inch, and in snowfall of about one- 
 half, i. e., from 32.8 to 15.93 feet. For Geneva a comparison of the last 
 11 years with the preceding period of 35 years shows an increase in 
 temperature of 1.134° F., and a decrease in the rainfall of 3.3 inches, 
 and therefore an annual decrease of ff = .3 inch. These changes, ac- 
 cording to the opinion of Plantamour, are due to the contraction or 
 decrease in the size of the glaciers which has been observed during the 
 last 12 years. 
 
 Now, as we found in the preceding paragraph, in my reply to E, from 
 the decrease in the height of water stages, that there was an average 
 annual decrease in the depth of rainfall in the valley of the Rhine above 
 Basle during the period from 1830 to 1808 of .0450" and during the 
 period of 10 years from 1857 to 1872 of .2730", the similarity of these 
 results, obtained from an entirely different source, to the decrease of 
 rainfall in the mountainous regions at Bodeubach and Geneva is sur- 
 prising. 
 
 *Ore. 
 
41 
 
 Several countries in Europe have, unfortunately however, only since 
 the last few years established meteorological stations in the forest and 
 mountain regions, and alter the lapse of several decades it is highly 
 probable that they will show the same decrease iii rainfall as at Boden- 
 bach and Geneva. 
 
 CONCLUSION. 
 
 As I now believe that I may assume that my theory in regard to the 
 decrease of water in springs and rivers, announced in L873, has been 
 established as a fixed fact by my discussion, and then by the tabular 
 exhibit of observations at 56 stations on 13 rivers, and finally by the 
 abundant opinions and thorough treatises of naturalists and experts 
 given by me, I take the liberty of making the most earnest request of 
 my readers and colleagues that each may labor in his own sphere, 
 so that the higher governments, authorities, corporations, land-owners, 
 and communities may finally be convinced of the numberless disad- 
 vantages and dangers our present cultivated countries are approach- 
 ing, if a limit is not sei; to the further devastation and destruc- 
 tion of forests, and that it is imperatively necessary to carry out, as 
 rapidly as possible, the precautions and measures recommended in my 
 treatise of 1873, and which have been also warmly approved by other 
 authorities, and thus prevent, as far as it yet lies in man's field of labor, 
 the calamity of a still further decrease of the water in springs and 
 rivers which threatens future generations. 
 
 Finally, I take the liberty of saying to my esteemed readers that I 
 am ready to furnish cheerfully all the data and results whieh 1 have 
 collected, and all the books and pamphlets which have been published 
 bearing upon this subject, for the examination and use of all such gen- 
 tlemen who intend to still more thoroughly investigate this hydraulic 
 question. 
 
 [Note by ili«' translator.] 
 
 In making the foregoing translation, 1 have attempted to make it as 
 literal as possible, and yet make it fairly intelligible English reading. 
 
 1 have used the word " rainfall" to indicate that term of the author 
 which literally translated would be "aqueous atmospheric precipita- 
 tions," and which includes rain, snow, hail, dew, &e. 
 
 I have also changed all the metric measures and eentrigrades into 
 American measures and degrees of Fahrenheit. 
 
 CJ. WEITZEL, 
 Major of Engineers, 
 Brevet Major-General, U. 8. A. 
 4 w 
 

 
I I j i i ■ .. 
 
 TABULAR EXHIBIT. 
 
 L„ ..„-.. 
 
 
PLOT 
 
 of ill.- calculated means of monthly, ai nl.higliosl and lowesl gauge readings 
 
 taken on the Rhine IWmi lil'iil In 1856 and 1857 Lo 1872. 
 
 Hlieel l. 
 
 
 - 
 
 m. ,,,, „r 
 
 is; <;■!:,.-, 
 
 is;:, -i i .\ 
 
 is;.-,, is.'o,. 
 
 I.VII/l'li i,,, 
 
 
 lh.,1,,,1 
 
 staaes whirl 
 
 = 
 
 L.W. 
 
 1353+3,15" 
 
 r.siiij ■i.oii ■ 
 
 If. II'. 
 
 //.'/.'/■.■'.no; 
 
 IS,. I ";.'/,V 
 
"', 
 
of ih<" liighestand lowesl aftd Elie calculated mean of (|anc|e-roadin<]s taken on the Rliinc al Emmerick 
 
 from #70 In 1873. 
 
 Ctfytpihd train Ihi hyilrmulir work of Dr.llBtrqliuit* nml 
 
 cMm /;■»,!, Mr. Khit/e lappcetor orllvdniuli,' „■„,■/,-, 
 
 .S'/zc// 
 
[ 
 
PLOT 
 
 of (he calculated means of moiLtM } r,annual,highest and lowest gauge -readings 
 taken on the Elbe duriug the periods mentioned 
 
 Sheet J. 
 
 
 frmn 1S3? to Igi 
 
 From lg.i.i toll?/ 
 
 L_ 
 
 TT- 
 
 T 
 
 AA 
 
 From K.J.;/,,//;, 
 
 A 
 
 
 Ilii/hr.H 
 
 Highest 
 
 stages 
 
 mo+I6'3,U 
 
 mS'M'1,5" 
 
 LoH'CS/ 
 
 stages 
 
 me-s'e,s" 
 
 II. w. 
 
 L.W. 
 
 mn-i-'j,6' 
 iscs- 5 /;.<)- 
 
 H.W. 
 
 l<?6U'ig,9~ 
 
 L. it: 
 
 1W !!■ 
 
 mss*ro.e' 
 
 Comparison of several low gauge- 
 readings taken al the different sta- 
 tions on the Blt)e with those taken 
 in 1842 the lowest year since 11316. 
 
 Y" 
 
 
 Mdnik 
 
 KauUmtz 
 
 Habitant: 
 
 All.ssiq 
 
 fctschen 
 
 Mii/irifriii/il 
 
 Dresden 
 
 Meissen 
 
 RCesa 
 
 MtllllhtTl, 
 
 T,„ v „u 
 
 Wittenberg 
 
 HossUu 
 
 Barby 
 
 Afaailcbura 
 
 llmilliiri, 
 
 1 7 ;//,„ lior.i- 
 Wmnd-mitm 
 
 filekede 
 
 I //cm f, -irmluiit 
 
 iliiruin tii lol„ rim, I X„i;ni/iiitR' 
 Atufiisll'/.ii 
 Xoicriilirr/A'-i* 
 September ISS9 
 Year 1873. 
 
s 
 
 LT 
 
C'A^/ /, 
 
 LQ 
 
Xha-f't, 
 
 Mean of 
 
 from i.itn; in (S3. 
 
 o. ss " 
 
 Mean »r 
 
 l<);„„ 1,1111, In IXi." 
 
 PLOT 
 of the highest and lowest as well as calculated moan, of gauge 
 taken on the Elbe at Dresden from 1806 to 1873 
 
 Mean „r 
 /■•run, ISM to 181 
 
 PLOT 
 
 orthe calculated monthly 
 
 mean of gauge-readings taken at Dresden 
 
 on the Elbe from 1806 to 1839 and lii'd) to 1873 
 
 Mean or 
 
 hi-iim l.i',ili,,l,\,:; 
 _- /■.!./• 
 
 /■i;,,,, ISiOtnlSK 
 
 
 \ 
 
 1 
 
 X | 
 
 -J 
 J. 
 
 t 
 
 i 
 
 f 
 
 1 
 
 i 
 
 I J 
 J 1 1 
 
 1 
 
 | 
 
 
 .1 
 
 0. 
 
 
 
 
 
 
 
 
 
 
 ■ 
 
 
 
 inn 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 thy i /}'"'/ (•_'/'' '•'■'' 
 
 [■'i„,„ /.n/ii„/,i,:/ 
 
i k 
 
PLOT 
 
 iifllic calculated mean of the monthly, yearly, Iiii 
 taken on the Danube in Hie peril 
 
 Shrrt. 
 
 lies! and lowest gauge-readintjs, 
 ds given herein. 
 
 tffi -m,, l,n, i.v at. 
 
 train lS351o 1854 
 
 /'>■„,„ tssstoisn 
 
 J± 
 
 \FroTib mOtolS', 
 
 ir,„„ isviirisy: 
 
 From i.\:,:it,.is;. 
 
 - ' ------ 
 
 .1 F 
 
 '( '' 
 
 ///,//„.<■/ ,„„//„„; J 
 Kitl,r.sl„,l,:v I 
 
 „./,„./, 
 
 i$38+sr.se 
 
 /Mi*/ ;i:/', " 
 
 stages 
 184-5- J "10" 
 
 A 
 
 l8b5+-l$'lt.Yg 
 
 Ke.?+ ni'a.v 
 
 1823-1 3;i 
 187/- a. ' 
 
 ll.ll'. 
 mm*. 't'i'ij,', 
 1862* /.r.iri'i " 
 
 T..W, 
 
 J.tM-'i 'l(l,'/S' 
 
 lillli : \. I -IT„,ll,l,IS 1,1 
 
 1'h'lL _ l'H-L'1'L l?5t, 
 From 1851. i„ 181 ', 
 
 A 
 
 .('mm M.lltaUSS. 
 
 /■'roll, 1X6.1 1., IX >; 
 
 //l,,/lr. r l„,o//,„r,,i 
 iv/iiWi 
 
 ffiqluxt 
 
 shuirs 
 
 WU+9'6SS" 
 
 m;:> + 1 ;'.•:;: u.<> 
 
 At 
 
 From lXit/l„IX.li 
 
 lovmst 
 stages 
 
 /.«.;- 6'3,5" 
 11X5-1/ !'. .Ha- 
 ll, w. 
 
 m3*iy'3,53" 
 
 1871+t8'8,8" 
 
 1858+ O 
 
 1866+ II. 
 
 11. W. 
 
 m;:, + ///'. 
 
 I860* 173,83" 
 
 1855-6, 3 " 
 
 isee-zuoM 
 

 I 
 
6 
 
Cross sections of flip Danube a( the bridge al Linz Austria 
 liikcn iu L850 and 1877. 
 
 Cross sections of the Danube between Pest and Ofentaken in L833 and 1.874 
 c^ before and after the constmclion of the chain bridge. 
 
 'Sheet (>'. 
 
 Xt/ti fi/r (/r.^iiiii 
 
 . . , , ""»■"""' <»< l/ir ,„;!,, ,„!,,■„, ,/„ ,,.„.„.. ,„■/,„„ .„„,/,/„■ daiomincUors indicate. Ih, death ulnn. 
 
 ■ilr fortai.a(hs= hZSOO 
 
 S,„/,. /,„■ //„>,/,.<■,.. I-. JUS.