My dear Sir,

I am much obliged for your essay which I have read with the greatest interest.¹ 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.² 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.³

My son George desires me to thank you for his copy and to say how much he has been interested by it.⁴

I remain, my dear Sir, | Yours very faithfully, | Charles Darwin.