16 Scientific Proceedings, Royal Dublin Society. 
From the nature of the operation, the frequent combination of 
two or more of these variations of strain, in similar and favour- 
able phases, and their consequent co-operation in producing 
helping stresses in the body of the earth, must evidently tend 
to promote further the yielding of the viscous mass, notwith- 
standing their being accompanied by partial interferences and 
unfavourable combinations. Perhaps even the greater changes 
of barometric pressure may be of some assistance. The tidal 
forces affect our globe to its inmost parts, though of course they 
diminish in the proportion of the distance from the centre. To 
these agitations we may add the geological disturbances proper, 
whatever their cause; though their effect in this respect must 
be slight. Their primary effect is, doubtless, the production of 
somewhat local irregularities of the surface; but, taken all 
together, they must tend to promote the settlement of the globe, 
as a whole, into its general mean figure of equilibrium. 
C.—The last argument, in our order of discussion, for the 
restriction of geological time, is that the present mean rise of 
temperature in descending the crust of the earth shows that 
“about 10,000,000 or (say at most) 15,000,000 of years” ago the 
surface of the earth had just consolidated. Professor Tait clearly 
prefers the ten millions; as we see not only from the words 
quoted, but from others also. Now, Sir William, in his famous 
paper on the Secular Cooling of the Globe, proposed to give us 
100,000,000 years and perhaps much more; probably it is owing to 
the influence of his sterner coadjutor that he has since cut us 
down to 90, or even 50. But observe that he still contemplates 
having to concede 90, that is to say, six times as much as 
Professor Tait would yield on compulsion, and nine times as 
much as he would grant willingly. Now, nine to one is rather 
a high proportion in a case of this kind; and when we note 
the discrepancy, it is calculated to lessen considerably the 
anxiety with which we listen to this argument for the restriction 
of geological time. May we not say, with the most profound 
respect for these two distinguished coadjutors, that if they had 
arrived at some consensus between themselves their opinions 
(for such alone they really are) on this point would have been 
entitled to greater weight? In a case of so wide divergence it 
would be delusive to adopt the mean of the results. The 
question is one of mathematical calculation, founded upon 
