192 EFFECTS OF FOBESTS ON SPEINGS AND RIVERS. 



which pour down large bodies of water when, and only when, there 

 have been dashes of rain, and from what has been stated it may be seen 

 that the prognostication is not without foundation when I allege that 

 if the causes which have, during the last 140 years, occasioned a 

 lowering of the water-level and diminution of the above-named five 

 European rivers shall go on operating in the time immediately before 

 us, the result will be that the level will be still further lowered and 

 the delivery diminished, until bye and bye they become so reduced 

 as to be unnavigable. 



" Although, beyond the results which have been published by Dr 

 Berghaus in his ' Hydrography,' which has been quoted, and which, 

 unhappily, are but little known, we have hitherto been unable to 

 obtain reliable compilations and comparisons of observations con- 

 tinued for many years of the water-level on the larger rivers, there 

 are men of observation and experience who, in consequence of what 

 they have noticed on some few rivers, have called attention to the 

 diminution of the water supply which is going on. An instance of 

 this we have in the following communication, which is well-deserving 

 of consideration, found in an article, by F. Perrot, in Deutsche Monat- 

 schrift fiir Handel, Schiff-fahrt. und Verhehrswesen (I. Band, Eostook, 

 1872). 



" A consideration of the three rivers — Weser, Elbe, and Oder — 

 makes clearly manifest a reduction in the quantity of water delivered 

 by them, and a silting up of the river-bed with sand. It has been 

 calculated that if the Elbe continue to diminish in the future at the 

 same rate at which it has been diminishing up to this time, it will soon 

 be impossible for heavily laden ships to pass by it. Nor is it otherwise 

 with the Oder ; in the very dry year 1858, there were only eleven days 

 in which the navigation of the Oder in Silesia could be carried on 

 with full force. The Weser delivers the smallest body of water of 

 the three. One principal reason for this is the destruction of forests 

 which has taken place on the heights which are found alongside of 

 the river, and which the Government have latterly taken steps to 

 prevent ; but still more than what has resulted from the destruction 

 of forests has been the consequence of the rectifications of the river-bed 

 which it has become a general practice to carry out. 



"After weighing fully the collected observations on the water 

 level, and consequences deduced from them in the foregoing treatise 

 I think no Hydroteohnik will venture to call in question the correct- 

 ness of the allegations advanced by the distinguished hydrographer 

 Dr Berghaus, iu the year 1835, which allegations have been confirmed 



