Down, June 1st, 1878.
I have at last found time to read [the] first chapter of your "Dolomit Riffe" (285/1.

"Dolomitriffe Sudtirols und Venetiens." Wien, 1878.), and 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, and 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 any one.

(285/2.

Published in "Life and Letters," III., pages 234, 235.) Nevertheless, I saw dimly that each bed in a formation could contain only the organisms proper to a certain depth, and to other there existing conditions, and that all the intermediate forms between one marine species and another could rarely be preserved in the same place and bed.