R. D. SALISBURY. The Greenland Expedition of 1895, Jour. Geol., vol. 3, 1895, pp. 875-902. E. V. DRYGALSKI. Grönland Expedition der Gesellschaft für Erdkunde zu Berlin 1891-1893, Berlin, 1897, 2 vols., pp. 551 and 571, pls. 53, maps 10. WILLIAM H. HOBBS. Characteristics of the Inland Ice of the Arctic Regions, Proc. Am. Phil. Soc., vol. 49, 1910, pp. 57-129, pls. 26-30. The Antarctic continental glacier:— R. F. SCOTT. The Voyage of the _Discovery_. London, 2 vols., 1905. E. H. SHACKLETON. The Heart of the Antarctic. London, 2 vols., 1910. E. VON DRYGALSKI. Zum Kontinent des eisigen Südens, Deutsche Südpolar-Expedition, Fahrten und Forschungen des “Gauss”, 1901-1903, Berlin, 1904, pp. 668, pls. 21. OTTO NORDENSKIÖLD and J. S. ANDERSSON. Antarctica or Two Years Amongst the Ice of the South Pole. London, 1905, pp. 608, illustrated. E. PHILIPPI. Ueber die fünf Landeis-Expeditionen, etc., Zeit. f. Gletscherk., vol. 2, 1907, pp. 1-21. Nourishment of continental glaciers:— WILLIAM H. HOBBS. Characteristics of the Inland Ice of the Arctic Regions, Proc. Am. Phil. Soc., vol. 49, 1910, pp. 96-110; The Ice Masses on and about the Antarctic Continent, Zeit. f. Gletscherk., vol. 5, 1910, pp. 107-120; Characteristics of Existing Glaciers. New York, 1911, pp. 143-161, 261-289. Pleistocene Glaciation of North America Viewed in the Light of our Knowledge of Existing Continental Glaciers, Bull. Am. Geogr. Soc., vol. 43, 1911, pp. 641-659. Field and pack ice:— EMMA DE LONG. The Voyage of the _Jeannette_, the ship and ice journals of George W. de Long, etc. Berlin, 1884, 2 vols., chart in back of vol. 1. ROBERT E. PEARY. The Discovery of the North Pole (for further references on both sea and pack ice and Antarctic shelf ice, consult Hobbs’s Characteristics of Existing Glaciers, pp. 210-213, 242-244). Icebergs:— WYVILLE THOMSON. Challenger Report, Narrative, vol. 1, 1865, Pt. i, pp. 431-432, pls. B-D. I. C. RUSSELL. An Expedition to Mt. St. Elias, Nat. Geogr. Mag., vol. 3, 1891, pp. 101-102, fig. 1. H. F. REID. Studies of Muir Glacier, Alaska, _ibid._, vol. 4, 1892, pp. 47-48. E. VON DRYGALSKI. Grönland-Expedition, etc., vol. 1, pp. 367-404. M. C. ENGELL. Ueber die Entstehung der Eisberge, Zeit. f. Gletscherk., vol. 5, 1910, pp. 112-132. CHAPTER XXII THE CONTINENTAL GLACIERS OF THE “ICE AGE” =Earlier cycles of glaciation.=—Our study of the rocks composing the outermost shell of the lithosphere tells us that in at least three widely separated periods of its history the earth has passed through cycles of glaciation during which considerable portions of its surface have been submerged beneath continental glaciers. The latest of these occurred in the yesterday of geology and has often been referred to as the “ice age”, because until quite recently it was supposed to be the only one of which a record was preserved.