252 DYNAMICAL GEOLOGY. 



ever, as Holland, states, are clean, but " now and then one is seen with 

 bowlders upon it; and here and there small bergs that are quite covered 

 with stones and gravel" (1877). 



Dr. Kane, describing the great pack of icebergs that occupies the center 

 of Baffin Bay, mentions that some were 300 feet high, and large numbers 

 over 200 feet ; 280 of the first magnitude (the most of them over 250 feet) 

 were in sight at one time. Taking the specific gravity of iceberg-ice at 0-886 

 (Holland), one ninth of the mass by weight is out of water. In the 

 Antarctic, the long ice-barrier observed by Captain Wilkes had a height 

 above the sea of 150 to 200 feet ; and some of the bergs were 300 feet high. 



(1) Icebergs are a means of transporting stones and earth from one 

 region to another; and those of Greenland make their farthest deposits in 

 the Atlantic about the banks of Newfoundland, or between the meridians of 

 of 44° and 52° and north of the parallel of 40° 30'. 



(2) When grounded on rocks, they may scratch the surface ; but closely 

 crowded and regular scratches, like those of glaciers, over large areas cannot 

 be made. An iceberg '' rocked by the swell of the sea, and sometimes turn- 

 ing over," could not be good at scoring submerged rocks. Moreover, rocks 

 over the sea-bottom where icebergs drop their freight of stones would seldom 

 be uncovered. 



The following are important works and memoirs on existing glaciers : — 



H. B. De Saussure: Voyage dans les Alpes, 4 vols., 1779-1796. 



Agassiz: Etudes sur les Glaciers, 8vo, Neuchatel, 1840. — Systhne Glaeiaire, Nou- 

 velles Etudes et Experiences sur les Glaciers Actuels, Bvo, with an Atlas of 3 maps and 9 

 plates, Paris, 1847. 



J. De Chaepentier : Essai sur les Glaciers et sur le Terrain Erratique du Bassin du 

 Bhone, 8vo, Lausanne, 1841. 



J. D. Forbes : Travels in the Alps of Savoy, etc., 8vo, Edinburgh, 1843. — Occasional 

 Papers on the Theory of Glaciers, 8vo, Edinburgh, 1859. 



J. Tyndall : The Glaciers of the Alps, 8vo, London (and Boston), 1861. — The 

 Forms of Water (in Appleton's International Series), 8vo, New York, 1872. 



A. Heim : Handbuch der Gletscherkunde, Stuttgart, 1885. 



N. S. Shaler and William M. Davis: Illustrations of the Earth'' s Surface; 'Glaciers, 

 a quarto volume containing 196 pages of text, with 25 fine plates mostly from pho- 

 tographs, 1881. 



The following relate to existing glaciers of the Pacific Coast of North America : — 



Davidson, on the first discovery of glaciers on the Pacific Coast — on Mount Rainier 

 (Tacoma), Mount Baker: Proc. Acad. California, iv. 161, 1871, and Am. Jour. Sc, III., 

 iv. 156, 1872. 



Clarence King: "Glaciers of the Pacific Coast" (on Mount Shasta, Mount Hood, 

 Mount Rainier, etc.). Am. Jour. Sc, III., i. 157, 1871, and "Report 40th Parallel," 

 vol. i. 462, 1878. 



John Muir : " Glaciers in California " (Sierra Nevada), Overland Monthly, 

 December, 1872. 



Joseph Le Conte : " Ancient Glaciers of the Sierra Nevada" (with notice of existing), 

 Am. Jour. Sc, IIL, v. 325, x. 156, xviii. 43, 44. 



G. F. Wright: The Ice Age in North America, 1889, 1891. 



