‘OCTOBER 13, 1899. ] 
other on the limitation of the age of the 
sun. 
These three lines of attack remain still 
those along which the assault from physics 
is delivered against the strongholds of 
geology. Lord Kelvin has repeatedly re- 
turned to the charge since 1868, his latest 
-contribution to the controversy having been 
pronounced two years ago.* While his 
physical arguments remain the same, the 
limits of time which he deduces from them 
have been successively diminished. The 
original maximum of 400 millions of years 
has now been restricted by him to not much 
more than 20 millions, while Professor Tait 
grudgingly allows something less than 10 
millions.+ 
Soon after the appearance of Lord Kel- 
vin’s indictment of modern geology in 1868, 
the defence of the science was taken up by 
Huxley, who happened at the time to be 
President of the Geological Society of Lon- 
don. In his own inimitably brilliant way, 
half seriously, half playfully, this doughty 
combatant, with evident relish, tossed the 
physical arguments to and fro in the eyes 
of his geological brethren, as a barrister 
may flourish his brief before a sympathetic 
jury. He was willing to admit that ‘‘the 
rapidity of rotation of the earth may be di- 
minishing, that the sun may be waxing dim, 
or that the earth itself may be cooling.’’ But 
he went on to add his suspicion that ‘‘ most 
of us are Gallios, ‘who care for none of 
these things,’ being of opinion that, true or 
fictitious, they have made no practical dif- 
ference to the earth, during the period of 
which a record is preserved in stratified de-. 
posits.’ t 
For the indifference which their advocate 
thus professed on their behalf most geolo- 
**Yhe Age of the Earth,’ being the Annual Ad- 
dress to the Victoria Institute, June 2, 1897. Scr- 
ENCE, May 12 and 19, 1899. Phil. Mag., 1899. 
} Recent Advances in Physical Science, p. 174. 
t Presidential Address. Quar. Journ. Geol. Soc. 
1869. 
SCIENCE. 
517 
gists believed that they had ample justifi- 
cation. The limits within which the phys- 
icist would circumscribe the earth’s history 
were so vague, yet so vast, that whether the 
time allowed were 400 millions or 100 
millions of years did not seem to them 
greatly to matter. After all, it was not the 
time that chiefly interested them, but the 
grand succession of events which the time 
had witnessed. That succession had been 
established on observations so abundant and 
so precise that it could withstand attack 
from any quarter, and it had taken as firm 
and lasting a place among the solid achieve- 
ments of science as could be claimed for any 
physical speculations whatsoever. Whether 
the time required for the transaction of this 
marvellous earth-history was some millions 
of years more, or some millions of years less, 
did not seem to the geologists to be a ques- 
tion on which their science stood in an- 
tagonism with the principles of natural 
philosophy, but one which the natural phi- 
losophers might be left to settle at their own 
good pleasure. 
For myself, I may be permitted here to 
say that I have never shared this feeling of 
indifference and unconeern. As far back as 
the year 1868, only a month after Lord 
Kelvin’s first presentation of his threefold 
argument in favor of limiting theage of the 
earth, I gave in my adhesion to the pro- 
priety of restricting the geological demands 
for time. I then showed that even the phe- 
nomena of denudation, which, from the 
time of Hutton downwards, had been most 
constantly and confidently appealed to in 
support of the inconceivably vast antiquity 
of our globe, might be accounted for, at the 
present rate of action, within such a period 
as 100 millions of years.* To my mind it 
has always seemed that whatever tends to 
* Trans. Geol. Soe. Glasgow, Vol. III. (March 26, 
1863), p. 189. Sir W. Thomson acknowledged my 
adhesion in his reply to Huxley’s criticism. Op. cit., 
p. 221. 
