Price.] -^^O [March 3, 17, & 



and cold; iv thawing; and regelatioii; so that climate may be too cold to make 

 glaciers. Thus in Upper Thibet, on the north side of the Himalayas, the 

 mean limit of i)erp('tual snow is not onl}' higher by more than a thousand 

 feet than on the south side, but the belt of snow is narrower, the back pres- 

 sure is less, and the snow deposited from the dry winds of Northern and 

 Middle Asia are so dry as to make it questionable whether there are any 

 proper glaciers, or anything more than the wee, or dry masses of snow in 

 in layers. Kec.lus, lOo-G; Professor Vogel, in Nature, March 16th, 1S76, p. 

 394. Yet the snow there is seventeen thousand to nineteen thousand feet 

 high, with a northern aspect. 



Tyndall shews that ice is not viscous; will not stretch, but is l)rittle and 

 will break under a strain, as when the glacier is compressed into a narrower 

 channel; or must make a descent or curve; when the continuitj^ is kept up 

 by a back pressure and regelation; freezing then becoming an agency in 

 wedging forward the mass in its shearing and descent. (Hours of E.vercise 

 on the Alps, ;3.^G, «fcc. ) Yet under presi^ure it conforms to the valley and 

 descends as if it were plastic. lb. 358, 359, 401. To consider the ditl'erence 

 between Tyndall and James D. Forbes, who held the theory of viscosity, is 

 not now material. They both were dealing -with the glacier in its cradle 

 on the side of the Alps, having an inclination of four to five degrees, with a 

 heavy incumbent pressure of the higher glacier, having a length of twenty 

 or thirty miles, a width from two or three miles where widest; in one in- 

 stance contracting from two thousand to 900 j-ards, with a depth sometimes 

 of six hundred feet. Yet the downward flow was so slow as to require 

 nice instrumental means to detect it, and though variable, owing to the 

 difference of inclination, or choking of gorges, the figures for the day of 

 twenty-four hours, most usually found are from twelve to twenty inches. 

 1 Lyell, 3G5, 3(5(5, 367. The flow is slower in winter than summer, and 

 faster at the centre than the sides, and at the top than at the bottom. 



It is apparent that the circumstances are not parallel with the supposed 

 icecap at the North Pole. The existing testimony is, that this is an open 

 sea; and if not that, is an ice covered sea, without land. There is not even 

 level lowland for the ice to form upon. There is no mountain to bring 

 the force of gravitation into operation. The ice that could saddle the pole 

 could have no tendency to move in any direction, for there is no inclined 

 plane. The hard frozen ice would not be borne downward by the weiglit 

 of higher ice; nor crevices be filled by regelation, thus to wedge forward the 

 frozen mass, as in high mountain regions. Greenland is a ridge of three 

 thousand to four thousand feet elevation, and that will make glaciers in the 

 valleys. But the supply of ice thence, or from Grinnell Land, or Labra- 

 dor, to reach Europe, must have hGun floating masses; and so as to the in- 

 terior of our country, if they came so far. 



Ice is, in another respect, less likely to descend by land to a lower latitude 

 from the pole, than if resting on a solid plane. Though the ice at a very 

 low temperature would not melt in the air, yet, resting on the water it 

 would become sodden, rot and sink ; and without land support could not 



