EXAMINATION OF STATEMENT BY HERR HAGEN. 183 



which explanation I would follow up with the remark that by the 

 Lake of Constance, which receives the waters of the Upper Khine 

 and afterwards emits them gradually, this river regulates its delivery 

 at lower-lying points ; and that, as a consequence of this, the reduc- 

 tion in its delivery at lowest, and in mean annual levels, can show 

 itself in but very minute measurements. 



" The circumstance that the fall, in these levels, shows itself much 

 more considerable at the pegel at Emmerich than at the pegel at 

 Cologne, is explained, by Bei'ghaus, by the fact that between Cologne 

 and Emmerich there flow into the Rhine the Wupper, the Ruhr, the 

 Emtsche, and the Lippe, which are less uniform in their flow than is 

 the Rhine which is thus fed. 



" Adverting now to the diagram and tabulated statement of the 

 level of the Rhine, as indicated by the pegel at Dusseldorf, situated 

 between Cologne and Emmerich, for the period from 1800 to 1871, 

 published by Herr Hagen, let us examine it with some care. 



" Herr Hagen found by his method of investigation that the 

 annual mean level had fallen upon an average about 1'6 line, which 

 for a period of 50 years gives a fall of 6'66 inches, 



" As according to the observations tabulated by Berghaus the fall 

 in the mean annual level given above reduced to a like period of 50 

 years gives at the pegel at Emmerich 24*88 inches, and at the pegel 

 at Cologne 7*91 inches ; from this it appears that Herr Hagen's 

 calculation of the fall of the water level at Dusseldorf, amounting to 

 6"66 inches, although founded on observations embracing a diff'erent 

 period of time, comes very near to the calculation made of the fall at 

 the comparatively proximate pegel at Cologne, from which it follows 

 that the calculated fall must be regarded as an actual fact, and not 

 an error in calculation, as Herr Hagen had intimated that it not 

 improbably might be. 



" Although according to the older tabulated observations of 

 Berghaus for the period from 1770 to 1835, there appears a some- 

 what higher rise in the highest floods of the Rhine, amounting to 

 from 10 to 18 lines, — still the calculation of Herr Hagen that the 

 level reached by the high floods had fallen 2-9'" per annum, and 

 consequently 12" V" in fifty years, may possibly be correct; and are 

 probably so, since in consequence of the extensive rectification of the 

 river bed between Basle and Manheim since 1830, the rapid flow of 

 the high floods must have been accelerated. 



"Herr Hagen has found a very slight rise in the level of the 

 lowest observations at Dusseldorf, about 0"2''' per annum, consequently 



