Dear Sir.

I have at last found time to read your first chapter of your Dolomit Riffe, & have been exceedingly interested by it. What a wonderful change in the future of geological chronology you indicate, by assuming the descent-theory to be established, & then taking the graduated changes of the same group of organisms as the true standard! I never hoped to live to see such a step even proposed by anyone.¹

Nevertheless I saw dimly that each bed in a formation could contain only the organisms—proper to a certain depth & to other there existing conditions and that all the intermediate forms between one marine species & another could rarely be preserved in the same place & bed—² Oppel, Neumayer³ & yourself will confer a lasting and admirable service on the noble science of Geology if you can spread your views so as to be generally known & accepted—

With respect to the continental & oceanic periods common to the whole N. hemisphere to which you refer, I have sometimes speculated that the present distribution of the land & sea over the world may have formerly been very different to what it now is; & that new genera & families may have been developed on the shores of isolated tracks in the South & afterwards spread to the North.⁴

With my best thanks for the present of your great works & with the highest respect | I remain, Dear Sir. | Yours faithfully— | Charles Darwin.