Manchester Memoirs, Vol. xliii. (1899), No. 5. 7 



general impression as to the hardness of ice is derived 

 from ice at or near its melting point. 



That this theory admits of experimental verification is 

 certain, but such experiments only become possible when 

 the general surroundings are at a temperature of 22''F. 



It was this consideration which caused me, in the first 

 instance, to delay any publication of the facts I observed 

 until there came a frost sufficient for my purpose. There 

 have been frosts of sufficient extent when my preparations 

 were not ready, and my preparations have been ready when 

 there were no frosts ; until, at last, my patience has given 

 way and I have determined to wait no longer. In taking 

 this decision, however, I have been greatly influenced by 

 my general observations on the effect of the temperature on 

 the ease of skating, and on the liability to slip. I notice that 

 without great care you cannot walk on ice at 31^° in 

 leather boots without nails, whereas you can walk safely 

 with boots with somewhat blunt nails under the same 

 circumstances; with a temperature of 27° you can walk 

 with leather boots almost as safely as on any polished 

 floor, while with somewhat blunt nails it is very unsafe to 

 walk on uneven ice. 



On ice near 32° skaters find no resistance however 

 slowly they may move, while on hard ice it is necessary to 

 move quickly, or the skates seize, showing that the ice 

 melts under the edge, but owing to the small area of the 

 lubricating surface, the lubricant is squeezed out rapidly, 

 thus destroying the lubrication below certain speeds, as in 

 Mr. Tower's experiment. 



But the circumstance that has most confirmed me in 

 the view that the slipperiness of ice is due to the lubrica- 

 tion afforded by the melting under pressure is a casual 

 but emphatic statement made by Dr. Nansen, in his book 

 on Greenland, that at the low temperatures he there 

 encountered the ice completely lost its slipperiness. 



