ABRASION OF THE SURFACES OF SOLIDS. 



167 



Table XII. Experiments on the Friction of Hide Leather. 

 Twelve pieces of hide leather were placed parallel to each other in a wooden 

 box, with one side loose so as to admit of being adjusted according to the 

 number of pieces of leather ; a bolt was then passed through the whole, and a 

 nut screwed on the end of the bolt so as to compress the pieces of leather 

 together and permit them to act on edge as one uniform surface ; which surface 

 was increased or diminished by putting in or taking out some of the pieces of 

 leather and screwing up the nut as before. 



Friction of 9 square inches of leather soaked in water, moving over a plate of iron. 



7 lbs. barely kept in motion 30 lbs. after starting with the hand. After remaining 5 minutes it took 

 to start it 291bs. 28 lbs. barely kept in motion 64lbs. after starting it, and after remaining one mi- 

 nute it took 42 lbs. to start it. 



Surface 1^ by 3 inches, equal to 4^ inches area. 



6ilbs. barely kept in motion 3 6 lbs. after starting it. After remaining 5 minutes it took 2 libs, 

 to start it. 21 lbs. barely kept in motion 64 lbs. after starting it. After remaining 5 minutes it took 

 38 lbs. to start it. 



REMARKS. — The friction of hide leather soaked in water appears to be greatly increased by time 

 and weight. This circumstance explains the enormous friction evinced in the pistons of pumps when 

 first put in motion. When the leather is not soaked, the resistance varies from one :|:th to nearly one 

 ^th of the pressure, and is diminished (caeteris paribus) by a diminution of surface. 



