TKEATI^^E BY HEBB WEX. 1 ( ( 



Amongst the objections referred to: — 1. Herr F. Hagen, Boyal 

 Prussian Geha/me Oherbaurath, and Oher-Zandes-Bau-Diredor, found 

 by actual measurement of the Rhine, at Dusseldorf, that the 

 diminution of the highest and of the medium floods was but incon- 

 siderable — on an average, the one 2'9 and the other 1'6 lines per 

 annum, about one-fourth and one-eighth of an inch. And he allies 

 that this may be accounted for by the modifications which have 

 been made in the river's bed, whereby the supplies from the 

 melting of ice have been retarded, and the flowing away of floods 

 promoted. 



2. Herr Maass, Prussian Boyal Hydraulic Inspector, has foxmd by 

 examination of the observations on the height of the Elbe, made for 

 143 years in the Fegel at Magdeburg, a considerable diminution 

 in the greatest, medium, and lowest heights of the river, amounting 

 to 17, to 35 J, and to 3i 20?^, or inches ; but he allies this reduction 

 to be the consequence of the modification of the bed of the river 

 occasioning a deepening of the bed, and an increased rapidity of 

 flow. 



3. A conjecture, which has been expressed, that such considerable 

 quantities of water may be carried away in the more frequent and 

 higher floods of later times as to compensate for the diminution in 

 the medium and lower heights of the flow at other times. 



The author shows — 1. By the measurements made by the late Herr 

 Grebenau, Bavarian Boyal Bau-Impecior, at Grermersheim, on the 

 peffd at Sondersheim, throughout a period of twenty-eight years, 

 which gave not only information in regard to the depth of the river, 

 as ascertained by the said gauge, but also in r^ard to the delivery 

 or quantity of the flow, that the diminution of the average depth 

 and a diminution in the delivery or flow go together. 



2. According to observations made by the EWe-Stromgchau-Coni- 

 misdon, it appears that there has been indeed a deepening of the 

 bed of the river in its upper part ; but, on the other hand, an eleva- 

 tion of the river bed by the silting of sand in the middle and the lower 

 portion of it. So that the diminution in the height of the water at 

 the gauge at Magdeburg cannot be attributed to a deepening of the 

 bed of the stream. 



3. That the high floods are no compensation for the diniinution of 

 the delivery by the low and medium flow is proved by the author — 

 first, by the before-mentioned measurements by the gauge at Sonders- 

 heim, according to which differences in the delivery are found to be 

 nearly proportionate to the depth of the flow; and, ftui;her, by 



