Chapter I. and II.--Elevation of the land: equability on E. coast as shown by terraces, page 19; length on W. coast, page 53; height at Valparaiso, page 32; number of periods of rest at Coquimbo, page 49; elevation within Human period near Lima greater than elsewhere observed; the discussion (page 41) on non-horizontality of terraces perhaps one of newest features--on formation of terraces rather newish. Chapter III., page 65.--Argument of horizontal elevation of Cordillera I believe new. I think the connection (page 54) between earthquake [shocks] and insensible rising important. Chapter IV.--The strangeness of the (Eocene) mammifers, co-existing with recent shells. Chapter V.--Curious pumiceous infusorial mudstone (page 118) of Patagonia; climate of old Tertiary period, page 134. The subject which has been most fertile in my mind is the discussion from page 135 to end of chapter on the accumulation of fossiliferous deposits. (556/3. The last section of Chapter V. treats of "the Absence of extensive modern Conchiferous Deposits in South America; and on the contemporaneousness of the older Tertiary Deposits at distant points being due to contemporaneous movements of subsidence." Darwin expresses the view that "the earth's surface oscillates up and down; and...during the elevatory movements there is but a small chance of durable fossiliferous deposits accumulating" (loc. cit., page 139).) Chapter VI.--Perhaps some facts on metamorphism, but chiefly on the layers in mica-slate, etc., being analogous to cleavage. Chapter VII.--The grand up-and-down movements (and vertical silicified trees) in the Cordillera: see summary, page 204 and page 240. Origin of the Claystone porphyry formation, page 170. Chapter VIII., page 224.--Mixture of Cretaceous and Oolitic forms (page 226)--great subsidence. I think (page 232) there is some novelty in discussion on axes of eruption and injection. (page 247) Continuous volcanic action in the Cordillera. I think the concluding summary (page 237) would show what are the most salient features in the book. LETTER 557. TO C. LYELL. Shrewsbury [August 10th, 1846].