314 SUPPORTING POWER OF SNOW ROOFS. 



the condition of the polar snows, however, show that 

 there are almost everywhere caverns, and open spaces, 

 existing" at the surface of the ground, underneath them. 

 This is a very curious and remarkable circumstance, 

 and one of high scientific interest, which at once 

 (assuming 1 its correctness) explains the facility with 

 which these little arctic animals live and thrive, in the 

 midst of a dreary waste of ice and snow, where appar- 

 ently no living" thing" could long" survive. 



That these hollow spaces do unquestionably exist 

 underneath the snow, is proved by the well-known 

 fact that persons walking about upon its surface, as 

 the summer draws on, frequently find large areas of 

 the snow field subsiding beneath their feet into these 

 caverns, showing that extensive hollows were there, 

 and that the snow does not everywhere rest solidly 

 upon the ground, but is merely supported upon columns 

 of it, here and there. Sir George Nares for instance, 

 mentions that 



"in July 1876, while walking above an extensive surface of 

 snow, it readily gave way and sank beneath us, with a 

 muffled noise, not only immediately under our feet, but a 

 large area of it acting in combination: how large we cannot 

 say, as no crack is visible in the neighbourhood." * 



The very considerable supporting power of snow roofs 

 and arches, used in the construction of snow houses, 

 is well known ; spaces of considerable extent being 

 able to be safely roofed in by hard snow, without 

 the necessity of interior support. For instance we are 

 informed by the same authority that in some houses, 

 erected for the Polar Expedition of 1875-6 



* Voyage to the Polar Sea, by Capt. Sir George Nares, R.N., 1878, 

 Vol. ii, p. 79. 



