On the Volume of the Niagara River, 21 



pound bodies ; and to question the compound nature of hy- 

 drogen."* 



Encouraged by these things, I, for one, will, in faith and 

 patience, abide the issue, ready and willing, should I again 

 see as much encouragement as I did last autumn, to spend 

 another winter, or many winters, in endeavouring to bring 

 about a consummation so devoutly to be wished, as the mani- 

 festation of the essential simplicity and unity of matter. 



On the Volume of the Niagara River, as deduced from Measure- 

 ments made in 1841. By Mr E. R. Blackwell; and call 

 culated by Z. Allen. 



Very little attention appears to have been hitherto bestowed 

 on the investigation of the comparative volumes of water dis- 

 charged by the great rivers of the globe. The relative amount 

 of the evaporation and drainage from the soils of different 

 countries, in proportion to the quantity of rain that falls upon 

 each, as denoted by rain-gauges, is also another interesting 

 subject connected with the preceding one ; for by measuring 

 the quantity of water discharged from a region of country 

 by the streams that drain it, and by deducting this quantity 

 from the whole amount that falls upon it, as indicated by rain- 

 gauges, the relative amount of evaporation may be ascertained. 

 The investigation of these facts forms the basis of a branch of 

 the science of hydrography, and leads to many useful as well 

 as curious and interesting inquiries. 



Whilst passing a few days at the Falls of Niagara, in the 

 summer of 1841, it occurred to me to make the necessary ad- 

 measurements for ascertaining the quantity of water precipi- 

 tated by the grand cataract, and drained from the vast area 

 of country bordering on the great lakes of North America. 

 This subject has long remained a mere matter of conjecture, 

 although unusual facilities are offered for making the ad- 

 measurement of the volume of this majestic river, from the 



* Experimental Researches, &c., shewing Carbon to be a compound 

 body made by Plants. By Robert Rigg, F.R.S. p. 264. 



