66 BUREAU OF AMERICAN ETHNOLOGY [bull. 54 



the recession. It is important to note, however, that most of the 

 ghxciers throughout the world which have been observed for any great 

 length of time have retreated during historic times, and most of them 

 are still retreating.^ As in case of the great lakes of the Southwest, 

 the retreat has not been absolutely continuous but has been inter- 

 rupted b}' occasional advances, though on the whole they may be said 

 to have been undergoing the process of retreat during the historic 

 period. The writers' actual observations of Arapahoe glacier in 

 Colorado cover a period of only one decade but show clearly that dur- 

 ing that time it has distinctly retreated. Mr. Enos A. Mills states 

 that the same is true of Hallett glacier. The numerous small ter- 

 mmal moraines of Fair glacier indicate that it has been retreating 

 rapidly for some time past. The terminal lakes at the foot of several 

 small glaciers and neve fields in Colorado indicate that they have 

 receded so recently that they have not yet been able to build new 

 terminal morames, even in case of Arapahoe and Hallet glaciers, 

 which are supplied with abundant morainal material from the cirque 

 walls. All of these facts point with great force to a continued desic- 

 cation of the region so near to northern New Mexico, and perhaps 

 also to very widespread desiccation. The same changes which would 

 operate to reduce the glaciers of Colorado would be exceedingly 

 likely to cause desiccation in the vicinity of the Jemez plateau. Of 

 course both temperature and wdnd affect the melting, and wind and 

 precipitation affect the accumulation of snow, but the most reasonable 

 explanation is that either precipitation has decreased or melting and 

 evaporation have increased (or more likely both), and the effect of 

 either would be desiccation. Actual observation has not been carried 

 on long enough in this region to afford safe evidence, but much safer 

 evidence is found in the present condition of terminal moraines and 

 terminal lakes. Regardless of whether desiccation is now in prog- 

 ress, it seems almost certain that desiccation has been in progress in 

 Colorado during the peiiod of human occupancy of the Southwest 

 and probably in the whole region under consideration. There is 

 no doubt that when the mountains near Santa Fe and northward 

 were glaciated more snow accumulated in the winter in the Jemez 

 Mountains. 



Some geologists ha^-e supposed that the glaciation of the Rocky 

 Mountains indicates the existence in the past of a colder climate 

 rather than of greater humidit3\ Careful consideration of the argu- 

 ments does not convince the writers of the correctness of this view. 

 Just now accumulation and dissipation of snow in the higher portions 



I See Reid, Harry Fielding, Studies of Mulr Glacier, Alaska, in Nat. Gcog. Mag., iv, 19-55, 1892; The 

 Variation of Glaciers, in Journ. Giol., m, 269-88, 1895; v, 378-83, 1897; \1, 473-7(3, 189S; vii, 217-25, 1S99; 

 vni, 154-59, 1900; ix, 250-54, 1901; x, 313-17, 1902; XI. 285-88, 1903; Xll, 252-03, 1904; xni, 313-18, 1905; XIV, 

 402-10, 1900; xvi, 4ii-55, C04-GS, i;«)S; x\ii, 007-71, 1909; XIX, 83-89, 454-61, 1911; Science, n. .s. in, 807, 

 189G; Henderson, Junius, Extinct and Existing Glaciers of Colorado, in Univ. Colo. Studies, vm, 02, 1910. 



