5 Pages in Charles Darwin's Library associated with "strata/epochs - chalk"

Lake Superior: its character, vegetation, and animals, compared with those of other similar regions.
By: Agassiz, Louis,
Publication info: Boston :Gould, Kendall & Lincoln,1850.
Pages: Page 258 Page 285 End Slip 2, side 2
A manual of elementary geology.
By: Lyell, Charles.
Publication info: [s.n.] :[s.n.],1855.
Pages: Page 251 Page 350