.270 GREENLAND OR POLAR ICE, 



is interrupted by numerous small globular or pear- 

 shaped air-bubbles : these frequently form con- 

 tinuous lines intersecting the ice in a direction 

 apparently perpendicular to its plane of forma- 

 tion. 



Fresh-water ice is fragile, but hard ; the edges 

 of a fractured part, are frequently so keen, as to 

 inflict a wound like glass. The homogeneous and 

 most transparent pieces, are capable of concen- 

 trating the rays of the sun, so as to produce a con- 

 siderable intensity of heat. With a lump of 

 ice, of by no means regular convexity, I have 

 frequently burnt wood, fired gunpowder, melted 

 lead, and lit the sailors' pipes, to their great 

 astonishment ; all of whom, who could procure 

 the needful articles, eagerly flocked around me, 

 for the satisfaction of smoking a pipe ignited by 

 such extraordinary means. Their astonishment 

 was increased, on observing, that the ice remained 

 firm and pellucid, whilst the solar rays emerging 

 therefrom, were so hot, that the hand could not 

 be kept longer in the focus, than for the space of 

 a few seconds. In the formation of these lenses, 

 I roughed them* with a small axe, which cut the 

 ice tolerably smooth ; I then scraped them with a 

 knife, and polished them merely by the warmth 

 of the hand, supporting them during the opera- 

 tion in a woollen glove. I once procured a piece 

 of the purest ice, so large, that a lens of sixteen 

 inches diameter was obtained out of it ^ unfortu- 



