BALCH— THE COUDERSPORT ICE MINE. 557 



cold retires to places low and subterranean, such as is this one, to which the 

 rays of the sun cannot approach, and that in such an aquatic and humid 

 place, it operates the results, which we have shown above. 



Since Poissenot's times, numerous scientific men have made hun- 

 dreds of observations in many of the several hundred glacieres 

 known, and their consensus of opinion is strongly in favor of the 

 winter's cold theory. 



In one respect the Ice Mine differs from some of the big European 

 glacieres, in which the size of the cavern and the nearness of the ice 

 to the mouth make it unnecessary for any other cold air than that 

 which comes through the mouth to get in to form the ice. For at 

 Coudersport the size of the shaft is hardly large enough to contain a 

 sufficient volume of very cold air long enough to do all the work 

 which evidently is done there. And therefore some further cause 

 must be sought. 



And this is found mainly in the fact that the side of the hill itself 

 at that spot, and not merely the Ice Mine, is a natural refrigerator. 

 When the shaft of the Mine was sunk ice was met in the rock 

 crevices. This is a not uncommon form of subterranean ice and 

 there are numerous examples of it both in the eastern and the western 

 United States.^ And the causes of its formation are evidently identi- 

 cal with that of the ice in caves, namely, the cold air of winter sinking 

 into the fissures in the rocks and the thaws of spring sending in 

 their waters. 



Now, at Coudersport there are unquestionably plenty of small 

 cracks or fissures in the rocks, else there could not be the layers of 

 ice which are found by digging there. And in these cracks much ice 

 undoubtedly is formed and stored in the spring. And from these 

 layers of ice in the hillside above the Mine freezing cold air must 

 keep sinking into the shaft as soon as the temperature in the shaft 

 begins to rise and continue forming ice in the shaft much longer than 

 would be the case without this extra supply. 



This function of rock crevice ice I must insist on here somewhat 

 forcibly, for although it has been noticed before, it has been so with 

 a lack of emphasis. And this is not surprising, for in many of the 



1 Edwin Swift Balch : "Glacieres or Freezing Caverns." Philadelphia. 

 Allen, Lane & Scott, 1900. 



