50 Joty—An Lstinate of the Geological Age of the Earth. 
The missing potash, if we assume the deficiency to be 1 per cent., would 
amount to 91 x 10“ tons. Assume that this is contained in the oceanic pre- 
cipitates now forming the ocean floor, and add it to the K,O now in solution in 
the ocean, or, more accurately, what is calculated on the amount of the chloride, 
the total is 968 x 10" tons. Compare this now with the sodium of the ocean 
calculated as soda, and amounting to 2100 x 10", and we have a ratio of 1 to 2°2. 
Had we assumed 0°8 as the missing percentage of potash, allowing such a 
deficiency as exists in the case of the soda to be accounted for by Glauconite and 
other marine deposits of the land, and estimating that the deficient 0°8 per cent. 
existed now in the sub-oceanic deposits, we find in the sea and its deposits 
796 x 10" tons. This bears to the soda the ratio of 1: 2°7, which fairly well 
agrees with the ratio obtaining in the alkalies of the rivers. 
From these figures we see that the deficiency indicated by the rocks is quite 
adequate to justify the supposition that the present alkah ratio of the rwers existed in 
the past. ‘To suppose the river-supply still less in the past is to make the record of 
the sedimentary rocks still more astray ; or, from another point of view, the record 
of the sedimentary rocks—if we accept the same data as agreed with the facts 
with regard to soda alkali—suggest that the rivers of the past must have dis- 
charged an equal, or even greater, amount of potash than at present. 
We may put the matter again in another way, which brings out more clearly 
the true nature of the evidence :—The ratio of the potash to the soda in the rivers, 
if preserved throughout the history of denudation, would account for the alkali 
relations of the primitive and the derived rocks. ‘This is independent of our 
estimate of Geological Time. The argument is, in fact, mainly directed against any 
assertion that the relative amounts of the alkalies supplied by the rivers of to-day 
is at variance with their probable past supplies. 
If this ratio has varied seriously in the long past, then a difficulty not easily 
surmounted has to be faced. The difficulty may be put thus:—The mean potash 
percentages of the parent and of the derived rocks are determinable, and the 
difference represents a certain amount of potash which may be considered, within 
limits, known. ‘This must have been removed from the parent rocks in some 
manner. If not by denudation, then in what manner? ‘The fact that we cannot 
estimate it in the sediments or in the sub-oceanic deposits appears legitimately 
referable to our ignorance. The assumption that the rivers supplied less potash 
in the past leaves the revelation of the rocks inexplicable. The assumption is 
made in order to explain what is really a hypothetical deficiency (that of the 
potassium in the oceanic reservoir), and renders inexplicable an actual known 
deficiency (that of the potassium in the rocks). 
The argument thus supports our Uniformitarian views by overbearing an 
objection often urged against the uniform supply of the constituents of the rivers. 
