178 EFFECTS OF FORESTS ON SPBINGS AND EIVERS. 



measurements made for thirty-two years on the Danube gauge at 

 Alt-Orsova, according to which is established not only a lowering in 

 the medium and the lowest flows, but also in those of greatest height, 

 which phenomenon, different from what has been seen in other rivers, 

 the author attributes to the circumstance that the floods in each of 

 the large tributaries occur at different times. 



" On the occasion of a Commission to prepare a scheme or project 

 for the regulation of the flow of the larger streams and rivers of 

 Austria being entrusted to me by the Government," writes Herr 

 Wex, " I set about, as a preliminary measure, the study of the 

 delivery of water by these rivers, and in doing so I have invariably 

 found that the delivery, measured by such appliances and means of 

 ascertaining this, has of late years greatly diminished. 



" Although a corresponding fact had been previously observed by 

 scientific students of natural history, and the phenomenon of a 

 diminution in the delivery of different rivers had been ascertained, 

 the correctness of the conclusion arrived at had been called in question 

 by other scientific men, and more especially by Hydrotechnikern 

 [hydrologists and students of hydraulic-engineering ?] I shall there- 

 fore state the views advanced by them, and thereafter meet them by 

 observations made during protracted periods on some of the principal 

 rivers of Central Europe. 



"Herr F. Hagen, Koyal Prussian Geheime Oberhaurath and Ober- 

 Landes-Bau-Birector, has in the last (the third) edition of his Hand- 

 buches der Wasserbau Kunst, for the year 1871, called in question the 

 correctness of observations hitherto made on the height of water in 

 streams and rivers, and of deductions drawn from these in regard to 

 a diminished flow of water in them, and he bases his opposing views 

 on observations made with the Rhine pegel at Dusseldorf since the 

 year 1800, and on the recorded observations on the height of the 

 level of the river for seventy-one years. 



"Herr Hagen has calculated for every separate year the arithmetical 

 riiean yielded by the daily observed height of the water, and also the 

 average annual height of the water, he has also noted the highest and 

 lowest heights of the water in each year; and he has represented 

 these three conditions of the water in a diagram, by which he makes 

 apparent that no very considerable diminution of the waters has 

 occurred. 



" In consequence of the great importance of the matter, Herr Hagen 

 has submitted the former selected observations on the state of the 

 river to a calculation founded on the least common multiple, and 



