T. C. Chamberlin. Chamberlin and Salisbury’s Geology, vol. 2, pp. 1-81.
Rigidity of the earth:—
Lord Kelvin. The Internal Condition of the Earth as to Temperature, Fluidity, and Rigidity, Popular Lectures and Addresses, vol. 2, pp. 299-318; Review of evidence regarding the physical condition of the earth, ibid., pp. 238-272.
Hobbs. Earthquakes (Appleton, New York, 1907), Chapters xvi and xvii.
Composition of the earth’s core and shell:—
O. C. Farrington. The Preterrestrial History of Meteorites, Jour. Geol., vol. 9, 1901, pp. 623-236.
E. S. Dana. Minerals and How to Study Them (a book for beginners in mineralogy). Wiley, New York, 1895.
On the nature of crystals:—
Victor Goldschmidt. Ueber das Wesen der Krystalle, Ostwalds Annalen der Naturphilosophie, vol. 9, 1909-1910, pp. 120-139, 368-419.