314 Scientific Intelligence. 



results are obtained than by reliance upon short sections in either 

 one by itself. 



Hanover, N. H., March 16, 1877. 



4. On Geological Time; by T. Mellard Reade. Presidential 

 Address before the Liverpool Geological Society. 28 pp. 8vo. 

 Liverpool, 1877.— In this paper, Mr. Reade has used the analyses 

 of river waters to determine the amount of mineral matter carried 

 •"in the laud. No finds that the amount of water run 

 off the area of Kn^iid and Wales annually is 68,450,936,960 tons, 

 equal to 18-3 inches in depth out of 31-988 inches of mean rainfall, 

 >•? inches for evaporation. The amount of solids in solu- 

 tion is 8,370,630 tons, or 12-23 parts in every 100,000 of water:— 

 in which are about 9-50 parts of carbonate* and sulphate of lime 

 and magnesia, 1*66 of chloride of sodium, 0-08 of nitrates and 0-99 

 of alkaline sulphates and carbonate of soda, silica and sesquioxid* 

 of iron. Estimating the solids in solution at 15 cubic feet to the 

 ton, the amount of denudation by solution would be '0077 feet 

 per century, or one foot in 12,978 years. Prestwich arrived at one 

 foot in 13,200 years, for the amount of carbonate of lime which 

 the Thames carries off from the Chalk, Upper Greensand, Oolitic 

 strata and Marlstone. The Thames, estimating the discharge at 

 8 in. per annum, and the total solids at 29-26, as given by Prest- 

 wich, removes 147 tons per square mile per annum ; and the 

 denudation over England 143-5 tons. 



Mr. Reade makes similar calculations for the rivers of Europe, 

 and finds that the Rhine removes about 92*3 tons per square mile ; 

 the Rhone about 232 tons; the Danube about 72*7 tons; giving 

 an average for the three rivers of 90 tons per square mile. The 

 Garonne removes 142 tons per square mile ; the Seine about 97 

 tons. From these data the conclusion is reached that probably- 

 over the world about 100 tons of rocky matter are dissolved by rain 

 ish square mile per annum: of which, as near as can now 

 - may be carbonate of lime, 20 tons sulphate 

 of lime, 7 silica, 4 each carbonate and sulphate of magnesia, 

 chloride of sodium, and 6 alkaline carbonates and sulphates. 



The amount of detritus brought down annually by the Danube 

 is about TnJ \ nr of the water, or tbre€ I amount of 



-olids in 5 iti.,i that of th Miss ^ip i- . i ling to Hum- 

 phreys and Abbott, T jVt «f the water. Mr. Reade adds : 

 _ " If we were to take the solids removed mechanically at six 

 times those in solution, which is a very high estimate, we should 

 have over the whole of the globe 600 tons of denuded matter 

 annually per square mile. Taking the sedimentary crust of the 

 ten miles thick throughout— a moderate estimate— and 

 allowing for the denudation of the sea and the amount added to 

 - by volcanic ejections, matter equal to one-third that 

 which is denuded from the land, we should have annually removed 

 and deposited matter equal to 800 tons per square mile of land 

 surface, or 40,800 million tons annually. The total surface of the 

 globe is 197 millions of English square miles. A cubic mile ot 



