474 



extend to a depth of ten and a-half feet in rear of one of the works 

 on the Ganges Canal that was under my orders. 



In the accompanying table I have compared the Irrawaddy with 

 a few of the largest rivers. (P. 476.) 



The discharge of the Ganges appears to me much too small ; for 

 I have seen both the Nile and the Ganges in flood, and should say 

 that the Ganges at Gazepoor is nearly three times the size of the 

 Nile. The proportions of earthy matter vary to a great extent in 

 all the above-mentioned rivers. The Ganges appears to convey the 

 largest proportion of silt and the Rhine the least. 



The power of a river in transporting earthy matter, however, 

 chiefly depends on the shape of the particles : sand, which is only 

 one-seventh the specific gravity of gold, will sink much faster in 

 water than gold leaf. By investigating this branch of the subject, 

 the power of water in motion to transport solid bodies may be dis- 

 covered, as the rate of sinking of any solid body must bear some pro- 

 portion to the velocity of the water required to transport that body. 

 It may here be also remarked, that where there is a strong current in 

 the ocean, rivers cannot push out deltas into the sea ; and rivers 

 which fall into tideless seas have no trumpet-shaped mouths, nor are 

 they easily navigated, for even the Mississippi has only fourteen feet 

 water at its mouth, though it is 170 feet deep higher up the river, 

 and the bar consists of soft mud. 



As a navigable stream the Irrawaddy is second to few rivers in 

 the world ; for not only are its mouths easily approached, but for 

 hundreds of miles up its course it has been found much more navi- 

 gable than the Ganges. The valley through which this noble river 

 flows equals, if it does not surpass Bengal in the richness of its soil ; 

 can it be doubted, therefore, but that ere long Anglo-Saxon enter- 

 prise, and civilization, will force its way into the interior of this rich 

 country ? 



P.S, — On this paper being read. Professor Forbes drew the atten- 

 tion of the Society to that part which related to the abrading power 

 of water at different velocities ; he stated that the experiments re- 

 ferred to were made fifty years ago by Professor Robison, his prede- 

 cessor ; and as the subject was of considerable interest, he hoped 

 some one would verify these experiments. 



Through his kindness in giving me the use of some of his instru- 



