robS°^] climate and evidence of cli:matic changes 65 



been observed for many years, particularly Great Salt Lake, which 

 is known to have increased its depth 11 feet and its area 600 square 

 miles from 1867 to 1871.^ Indeed, the history of the landlocked 

 lakes of the Southwest whose records have been found shows con- 

 stant fluctuation during the last half century, rather than progres- 

 sive change m one direction; but any progressive change would be 

 masked by the fluctuations and would be so slow that half a century 

 is not sufficient to show it. The ancient embankments, bars, and 

 other features of the old lake basins are so fresh as to mdicate com- 

 paratively recent retreat; and if, during a large part of the last 500 

 or 1,000 centuries, an infinitely slow change has been going on, 

 as indicated by the e^'idence, there is no reason to suppose that 

 anytlihig has happened to check the desiccation. 



At the present time the ratio of precipitation to dissipation is such 

 in the West and the Southwest that glaciers can not exist where they 

 were once abundant. One glacier 7 miles long extended down to 

 an altitude of 9,200 feet in the mountains near Santa Fe and several 

 smaller ones existed there. Not far northward the San Juan and the 

 Sangre de Cristo mountains and nearly the whole crest of the Conti- 

 nental Divide in Colorado were all heavily glaciated. The literature 

 of the subject is very voluminous, but only a few of the more impor- 

 tant papers need to be cited.^ The high sierras in California and the 

 Wasatch Mountains in Utah, together with the mountains of Oregon, 

 Washmgton, Idaho, Montana, and northw^ard, albhad their systems of 

 glaciers. Now no glaciers exist in New Mexico or Utah, only a few 

 very small ones are found in Colorado,^ while the glaciers of Califor- 

 nia, Montana, Wyoming, those of nearly the whole of North America, 

 indeed, have shrunken much from their former dimensions. There is 

 no way of knowmg just when most of the shrinkage occurred, but 

 the freshness of moraines and of glacial polish and striae on easily 

 weathered surfaces has convinced nearly all observers that the 

 glaciers of the southern Rockies were extensive at a very late period 

 in the Glacial epoch and that the whole retreat has been geologically 

 recent. This means some thousands of yer.rs for the greater part of 



iSee Gilbert's and RusseU's monographs, op. cit.; also Powell, J. W., Report on Lands of the Arid 

 Region of the United States, 1879. 



2 See Salisbury, RoUin D., Glacial Work in the Western Mountains in 1901, in Journ. Geol., ix, 71S-31, 

 1901: Stone, George 11., Remarks on the Glaciation of the Rock>- Mountains, Monogr. U. S. Geol. Surv., 

 XXXIV, 3.38-.54, 1899; Siebenthal, C. E., Notes on Glaciation in the Sangre de Cristo Range, Colorado, in 

 Journ. Geol., xv, 15-22, 1907; llowe, Ernest, and Cross, Whitman, Glacial Phenomena of the San Juan 

 Mountains, Colorado, in Bull. Geol. Soc. Amer., xvn, 251-74, 1900; Hills, K. C, Extinct Glaciers of the 

 San Juan Mountains, Colorado, in Proc. Colo. Set. Soc, i, 39-40, 1S83; Amcr. Journ. ScL, 3d ser., xxvn, 

 391-90, 1884. 



3 See Stone, George II., A Living Glacier on Hague's Peak, Colorado, in Science, x, 153-54, 1887; Lee, 

 Willis T., The Glacier of Mt. Arapahoe, Colorado, in Journ. Geol., vm, 047-54, 1900; Feimeman, N. M., 

 The Arapahoe Glacier in 1902, ihid., x, 839-51, 1902; Siebenthal, C. E., Notes on Glaciation in the Sangre 

 de Cristo Range, Colorado, Journ. Geol, xv, 15-22, 1907; Henderson, Junius, Extinct and Existing Glaciers 

 of Colorado, Univ. Colo. Studies, vni, 60-70, 1910. 



67519°— Bull. 54—13 5 



