From Charles Lyell 7 May 1860
53, Harley St. London. W.
May 7. 1860
My dear Darwin
I saw Salters spirifers, a very good proof of the fructifying nature of your indefinite modifiability principle.1 I also asked him if he did not think that Barrandes “primordial” (the Cambrian of Manual 5th. Edn. ) was getting more & more separated from Lower Silurian—2 He replied certainly— I am beginning to think the gap was enormous between them. And then there are the Huronian & Laurentian each with rippled sands 1000ds. of feet thick unconformable to the Potsdam or “primordial”.3 The latter I hear has just been found by Cassiano del Prado in some part of Spain.4
Suppose the gap as I begin to suspect to be as great as between Cretaceous & Eocene what a grand discovery the Cambrian type is—
On Wednesday May 16th. we expect a large meeting of the Geol. Socy in the hall in Burlington House when Lartet’s paper5 on contemporaneity of
Saw Salter’s Spirifer specimens; a very good proof of indefinite modifiability.
Beginning to think gap between Cambrian and Lower Silurian enormous.
Édouard Lartet to give paper before Geological Society ["On coexistence of man with certain extinct quadrupeds", Q. J. Geol. Soc. Lond. 16 (1859–60): 471–5].