HEPOBT BY ACADEMY OF SCIENCi: OP VIENNA. 199 



There follows a chapter devoted to the consideration of measures 

 proposed with a view, on the one hand, to prevent continaed and ever 

 extending devastation occasioned by inundations ; and on the other 

 to arrest and prevent the continuous diminution of water in springs 

 and in rivers in their lowest state, and in their mean delivery. But 

 it is the facts of the case established in regard to the effects of forests 

 on rivers and springs with which alone we have at present to do. 



The paper was subsequently published, and it excited much interest. 

 By several learned Societies Commissioners were appointed to report 

 upon it. Amongst others this was done by the Royal and Imperial 

 Academy of Science of Vienna, and the Imperial Academy of Science 

 of St Petersburg. It was also favourably considered and approved 

 by the Society of Engineers and Architects of Vienna, the Geogra- 

 phical Society of Vienna, the Forest Academy of Mariabrun, by 

 several Polytechnic Schools, and by many men of science. 



In regard to the views of Herr Wex relative to the phenomena 

 observed, the Commission appointed by the Academy of Science of 

 Vienna reported : — - 



" In view of the facts brought forward by the author, the Commission 

 has come to the conclusion that the diminution seen within the last 

 eerniury, in the medium and lower heights of the rivers made the subject 

 of observation, is attrihutahh to a diminution in the annual delivery of 

 these rivers. 



" The author finds that the diminution of the quantity of water in 

 the river is attributable to a diminution in the quantity of water 

 yielded by springs, of which he finds additional indications in the 

 diminution of water in streamlets, aqueducts, and wells. 



" The Commissioners agree with the author in this view, considering 

 the low depth of water in the rivers to be justly attributable to the 

 quantity of water flowing throughout the whole district constituting 

 the basin of the river having been reduced. 



" The causes of this general diminution in the flow of water may be 



found 1. In a diminution of the annual rainfall, connected with the 



extension of agriculture occasioned by the clearing away of forests ; 

 2. In an increased evaporation from the surface of the soil, consequent 

 on the change of culture spoken of ; 3. In such a change in the mode 

 of flow that the rainfall, instead of being, for the most part, retained 

 for a time and percolating through the gravel, flows away quickly, 

 producing brief periods of high floods, alternating with protracted 

 periods of drought." 



