6 Reynolds, On the SHpperiness of Ice. 



one was laughing at me — I found that I could not 

 call any mention of the subject. And then, in self- 

 extenuation, I reflected that water was not recognised 

 as a lubricant, so that even James Thomson himself, or his 

 brother, Lord Kelvin, might have failed to realize that the 

 melting of the ice under the pressure of the skate would 

 lubricate the moving skate, and rendered the ice slippery 

 to any hard body pressed against it. I also reflected, 

 that had not my mind been full of the circumstances of 

 lubrication, including the lubricating properties of all 

 fluids, I should not have recognised in the slipping of the 

 hot iron the action of the lubricant, and that, even if 

 I had, I should not have attributed like properties to 

 melted ice. 



Of course, this evidence as to the cause of the slipperi- 

 ness was altogether one-sided, and it was still open for ice to 

 have other properties which would account for the slipping 

 besides the property of melting under pressure, and it was 

 at once plain that to render the evidence complete it was 

 necessary to show that, under circumstances of tempera- 

 ture and pressure such that the pressure was nowhere 

 sufficient to melt the ice, the property of perfect slipperi- 

 ness of ice did not exist. 



Looking carefully into the matter from the theoretical 

 side, with Lord Kelvin's determination of the laws of the 

 melting point, 0'0I4° F. for each additional atmosphere, 

 it appeared that taking a weight of 140 lbs., and an area 

 of i-4/io(= 1/7) square inch, a man skating would melt ice 

 of 31^ F. with a skate-bearing of 1*4/10 square inch, while 

 to melt ice at a temperature of 22*^ F. the bearing must 

 be reduced 1-4/100 (= 1/70) square inch. That is, the ice 

 at 22*^ F. would have to be able to sustain a pressure up 

 to 10,000 lbs. on the square inch. That ice should stand 

 such pressure at first sight seems unlikely, but then our 



