Permanence of Oceans and Continents." "Geol. Mag." Volume X., page 309,
1883.) It appears to me almost monstrous that Professor Tait should say
that the duration of the world has not exceeded ten million years. (545/2.
"Lecture on Some Recent Advances in Physical Science," by P.G. Tait,
London, 1876.) The argument which seems the most weighty in favour of the
belief that no great number of millions of years have elapsed since the
world was inhabited by living creatures is the rate at which the
temperature of the crust increases, and I wish that I could see this
argument answered.


LETTER 546. TO J. CROLL.
Down, August 9th, 1877.

I am much obliged for your essay, which I have read with the greatest
interest. With respect to the geological part, I have long wished to see
the evidence collected on the time required for denudation, and you have
done it admirably. (546/1. In a paper "On the Tidal Retardation Argument
for the Age of the Earth" ("Brit. Assoc. Report," 1876, page 88), Croll
reverts to the influence of subaerial denudation in altering the form of
the earth as an objection to the argument from tidal retardation. He had
previously dealt with this subject in "Climate and Time," Chapter XX.,
London, 1875.) I wish some one would in a like spirit compare the
thickness of sedimentary rocks with the quickest estimated rate of
deposition by a large river, and other such evidence. Your main argument
with respect to the sun seems to me very striking.

My son George desires me to thank you for his copy, and to say how much he
has been interested by it.