EXTINCT AND EXISTING GLACIERS OF 

 COLORADO 



By Junius Henderson 



CONTENTS 



Definition and characteristics, p. jj. 

 Economic relations, p. 48. 

 Historical, p. 4g. 

 Extinct glaciers, p. 51. 

 Existing glaciers, p. 60. 



Definition and Characteristics 



Exact definition of the term "glacier" seems virtually impossible. 

 From the nature of the case, there must be many ice-masses which 

 are clearly glaciers, others certainly not glaciers, and others so near 

 the border-land between glaciers and non-glacial ice-bodies that it is 

 purely a matter of individual opinion as to whether the term is appli- 

 cable. Such cases are common. Thus, no hard and fast line divides 

 ''long" and "short," "big" and "Httle," "mountain" and "hill," 

 "river" and "rivulet." We may easily see why exact definition is 

 impossible in a region in which the accumulation of snow and the 

 melting are exactly balanced so that just before the fresh snow begins 

 to fall in autumn the last drift disappears. If in such a case the rela- 

 tion of dissipation to the accumulation of snow should be slightly 

 changed, as by a decrease in the mean summer temperature, or an 

 increase in the annual snowfall, or a change in the direction or velocity 

 of the prevailing winds, then we should have a small portion of the 

 largest drift left over each autumn and added to the following winter's 

 drift. Thus by repeated accretions, the drift would in time become 

 a large and deep snow-field which would soon become ice, and when 

 it reached a depth so great that the pressure of the column would over- 

 come the molecular resistance of the ice, it would begin to "flow" 

 or spread outward. In case of the accumulation on the side of a 



32, 



