THE CAUSE OF THE GLACIAL PERIOD. 507 



three thousand feet higher than now ; * and the same author 

 shows that in interglacial time tropical animals passed from 

 Barbary into Spain upon land where now the Strait of Gi- 

 braltar has a depth of one thousand feet, f These changes in 

 the relations of land and sea can not be ascribed to glacia- 

 tion, but seem to be distortions of the earth's form, such as 

 may be attributed to the action of strain upon the crust by 

 which the earth can become reduced in volume through the 

 subsidence and elevation of extensive areas during intervals 

 between epochs of mountain-building. In the same class of 

 changes are also to be included, wholly or in part, the post- 

 glacial elevation of Grinnell Land and the northwestern coast 

 of Greenland, one thousand to sixteen hundred feet ; J post- 

 Pliocene upward movements of two thousand feet or more in 

 Jamaica and Cuba ; * the recent uplift of the coast of Peru at 

 least twenty-nine hundred feet,|| which in diminished amount 

 seems to extend along the whole range of the Andes ; its prob- 

 able connection with the upheaval of the Cordilleras of North 

 America, where Le Conte believes that the elevatory move- 

 ments reached their greatest intensity in early Quaternary 

 time, causing a rise of several thousands of feet in the Sierra 

 Nevada ; A and the apparently correlative subsidence of a great 



* "Prehistoric Europe," pp. 513-522, and 568, with Plate E. 



+ " Prehistoric Europe," pp. 325, 337-339 ; " Quarterly Journal of the Geo- 

 logical Society," vol. xxxiv, 1878, p. 505. 



X "Quarterly Journal of Geological Society," vol. xxxiv, 1878, p. 66; "Geo- 

 logical Magazine," III, vol. i, 1884, p. 522. 



* J. G. Sawkins, " Reports on the Geology of Jamaica," 1869, pp. 22, 23, 

 307, 311, 324-329; W. 0. Crosby, "On the Mountains of Eastern Cuba," " Ap- 

 palachia," vol. iii, pp. 129-142. Compare William M. Gabb's memoir, " On the 

 Topography and Geology of Santo Domingo," " Transactions of the American 

 Philosophical Society," vol. xv, pp. 103-111. 



I A. Agassiz, " Proceedings of the American Academy of ^Arts and Sciences," 

 vol. xi, 1876, p. 287: and "Bulletin of the Museum of Comparative Zoology, at 

 Harvard College," vol. iii, pp. 287-290. Above this height, at which corals are 

 found attached to rocks, recent elevation of much greater amount seems to be 

 indicated by terraces, by saline deposits, and by the presence of eight species of 

 Allorchestes — a genus of marine Crustacea, in Lake Titicaca, 12,500 feet above 

 the sea. 



A "American Journal of Science," III, vol. xxxii, pp. 167-181, September, 

 1886. 



