Vice-President’s Address. 969 
We have next to consider what evidence we have regarding 
the rate at which lime-salts are being supplied to the sea 
through the agency of rivers. Dr John Murray, in his 
“Total Annual Rainfall of the Land of the Globe, and the 
Relation of Rainfall to the Annual Discharge of Rivers,” 
Royal Scottish Geographical Magazine, iii., pp. 65-77, gives a 
mass of data of the highest possible value in this respect. 
From Dr Murray’s tables, Mr C. D. Walcott, in his “ Address 
to Section E of the American Association for the Advance- 
ment of Science” (August 1893), has computed “113 tons as 
the total amount of matter in solution discharged into the 
Atlantic basin per annum from each square mile of area 
drained into it. Of this, 49 tons consist of carbonate of lime 
and 5°5 tons of sulphate and phosphate of lime.” In a foot- 
note Mr Walcott gives an abstract of Dr Murray’s figures as 
follows :—“ Total amount removed in solution per annum by 
rivers, 762,587 tons per cubic mile of river-water. Total 
discharge of river-water per annum into the Atlantic, 3947 
cubic miles. Area drained, 26,400,000 square miles. 
Amount of carbonate of lime per annum, 326,710 tons per 
cubic mile of river-water ; of sulphate of lime and phosphate 
of lime, 37,274 tons.” Dr Murray’s Table VIL, op. cit., p. 76, 
gives the proportion of the two latter salts as Ca,P,O,, 
2913 tons, and CaSO,, 34,361 tons per cubic mile. Mr 
Wilbert Goodchild has computed for me the total quantity 
which these would represent if converted into CaCO,. This 
comes to 4145 tons from the phosphate and sulphate, which, 
added to the 49 tons of carbonate of lime, gives as the total 
53143 tons of carbonate of lime from each square mile of 
land surface per annum. The figures, it will be noted, are 
less than those given by Mellard Reade in his “ Chemical 
Denudation in Relation to Geological Time,” Proc. Liverpool 
Geol. Soc., vol. iii., pp. 212-235 (1877). Further computa- 
tion shows that, if we assume that 12°5 cubic feet of limestone 
go to the ton, this total quantity represents 664°3 cubic feet, 
which, if distributed over an area equal to that whence it 
has been derived, would, at the present rate of delivery 
by rivers, require 41,985 years for the accumulation of a 
thickness of a single foot. 
