552 Remarks on the 



Now as a wine quart of water weighs 14545 grains, we have about 

 ~~th part of solid matter by weight. But as the specific gravity of 

 this cannot be stated at less than 2, we have jjgg th part in bulk for the 

 solid matter discharged, or 577 cubic feet per second. This gives a 

 total of 6,082,041,600 cubic feet for the discharge in the 122 days of 

 the rains : — 7.8 grains per nine quarts was the weight determined for 

 the five winter months or j^th part in weight, and g-g^th part in 

 bulk, which gives 19 cubic feet per second, or a total of 247,881,600 

 cubic feet for the whole 151 days of that period : 3.8 grains per wine 

 quart was the weight allowed for the three hot months, which gives a 

 g^th part by weight, and a 7 -g^th part by bulk, or about 408 cubic 

 feet per second for the discharge of solid matter, and a total of 

 38,154,240 cubic feet for the discharge during the 92 days. The total 

 annual discharge then would be 6,368,077,440 cubic feet."* Now it 

 is easily conceivable, since there is such a difference in the volume and 

 velocity of the river during the three periods here pointed out, that 

 the nature of their deposits must vary considerably likewise ; for since 

 we perceive a difference of 19,355 feet per hour in the velocity of the 

 stream between the rainy and summer months, it is at once apparent 

 that the one period would have the power of transporting much heavier 

 and greater quantities of matter than the other, and therefore of giving 

 origin to strata differing from each other both in composition and 

 thickness. 



It would appear, moreover, that the admixture of the marine fluid 

 with the turbid waters of rivers, has always had a tendency to produce 

 calcareous deposits enclosing the exuviae of fresh waters. These are 

 called " lacustrine limestones," from their containing lacustrine exuviae, 

 but it does not appear to have been taken into consideration, that some 

 cause is necessary to be assigned for the formation of the limestone, 

 since all our experience tends to shew, that the proper deposits of rivers 

 and other fresh waters are sands and clays ; sometimes it is true calcare- 

 ous matter is intermixed, but in such cases the probabilities are in 

 favour of its having been imbibed by the waters in their passage over 

 calcareous rocks. 



Besides, the occurrence of such genera as Melania, Paludina, Planor- 

 bis, Unio, Cyclas, and others is no proof whatever of the lacustrine ori- 

 gin of those limestones which contain them, for in tropical countries such 

 as those in which the secondaries are thought from their fossils to have 



* Journal of the Asiatic Society, vol. i. p. 241. 



