SUTHERLAND, DAVIs' STRAIT AND BAFFIN's BAY. 3.^9 



glacier to be equally smooth. On the north side of Cape Clarence 

 in the north shore of Jones' Sound, during the late voyage of the 

 " Isabel," I observed that one portion of the surface of a flat but 

 extensive glacier, that protruded several miles into Glacier Strait, 

 was exceedingly smooth, while another portion of it was so rough 

 and pinnacled that to walk over it would have been impossible. 

 This roughness must be attributed to some peculiar atmospheric 

 cause, or to the difference of temperature between the surface and 

 the interior of the glacier. 



Eight feet is the depth to which a minimum temperature of 

 — 45°, a monthly mean of— 30°, or an annual mean temperature of 

 + 2*5°, extended the freezing-point of water through freshwater 

 ice on a lake of two fathoms' depth (Kate- Austin's Lake) in lat. 

 74° 40' and long. 94° 16'. If we can presume the heat-conducting 

 power of ice formed on the surface of water, and of glacier-ice, to be 

 the same, then the temperature of the interior of the glacier below 

 the above depth, with the same minimum or mean annual degree 

 of cold, would be about -|-32°. The surface exposed to any alter- 

 nation of heat and cold, from the freezing-point to — 45° or many 

 degrees lower, would necessarily become contorted and disturbed 

 by contraction and expansion, even supposing its base or supporting 

 part were standing still. Of this we had unexceptionable proofs 

 in the condition of the surface of the ice on the lake already 

 noticed. But when we take into account that the whole bulk of 

 the glacier, except a few feet of its upper surface, retains its 

 plasticity and continues its downward motion, it need not be 

 wondered that the latter, hard and friable, assumes a broken-up 

 appearance. This view, however, does not fully satisfy us, not 

 being universally applicable. 



Following the example of Mr. Christie, one of the Secretaries 

 of the Boyal Society,* during a winter in Barrow Strait, I per- 

 formed a number of experiments by submitting water in a strong 

 iron bottle to various temperatures, from +82° to — 45°. While 

 the temperature to which the bottle containing the water was 

 exposed did not descend more than eight or ten degrees below the 

 freezing point, the column of ice, ascending through the orifice or 

 **fuze hole," and always amounting to about one tenth of the 

 whole mass of water used, retained its cohesive property so perfectly 

 that without being broken, and although only half an inch in 

 diameter, the whole apparatus weighing four to five pounds could 

 be raised by its means, and sometimes even inverted. But at lower 

 temperatures the ascending column escaped with a slight crepitating 

 sound, and frequently with explosive reports, accompanied each by 

 •a sudden propulsion of a portion of it to a distance of several feet ; 

 it was so friable too that it separated into discs of half or a quarter 

 of an inch in thickness, and sometimes crumbled to fragments 

 between the fingers. The important points, relative to the plasticity 

 ^of ice, contested some years ago by Prof. J. Forbes and Mr. Hop- 

 kins come within this field of research ; they are well known, and 

 need not be recounted here. 



* Ly ell's Principles of Geology, Seventh Edition, p. 226. 



