102 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



crease in the flood waters in cultivated lands, has lately been 

 the subject of a report by the Vienna Academy of Science, 

 from which it would appear that the diminution experienced 

 in the course of the last few centuries in the average height of 

 the water (especially the low waters) of the Rhine, the Elbe, 

 and other rivers of Europe, is to be attributed to a diminu- 

 tion in the annual quantity of water available for the rivers, 

 and taking account of the amount of evaporation, there still 

 results a diminution in the amount of water supplied by 

 springs and rainfalls. It appears to the commission prob- 

 able that the influence of forests is perceptible on the an- 

 nual rainfall, and especially on the distribution of the rain 

 throughout the year, although direct observations do not yet 

 suffice to determine the magnitude of this influence. Among 

 the causes tending to this diminution of the water in the 

 rivers, the commission enumerate, first, the extinction of the 

 forests, which exerted a beneficial influence in maintaining 

 and elevating humidity, in diminishing the extremes of tern- 

 perature, and diminishing the evaporation, and in assisting 

 to a more equable drainage of the precipitation. A second 

 cause is found in the drying up of the lakes, ditches, and mo- 

 rasses, which also would have exerted an influence similar to 

 that of the forests. Third, in the cultivation of extended 

 areas of land, which cultivation demands the consumption 

 of considerable quantities of water. Fourth, in the increase 

 of population, although the effect of such increase can directly 

 account for only a slight percentage of the entire diminution. 

 Finally, the commission consider the suggestion of Salmann 

 as worthy of consideration, according to whom water is be- 

 ing employed in the interior of the earth in the formation of 

 minerals which contain that liquid in chemical combination. 

 In view of these considerations, the commission recommend 

 that the Austrian government institute such observations as 

 will lead to a further knowledge on this subject, and especial- 

 ly take such steps as will prevent the further diminution of 

 water from becoming a calamity to future generations. Ef- 

 forts will also be made to collect more complete data from 

 the inhabited portions of the world ; and especially is the 

 hope expressed that the Viceroy of Egypt may cause tables 

 and graphic representations to be made of the observations 

 on the height of the water at the Kilometer at Cairo, where 



