32 



MECHANICS. 



which caused the friction being upwards that in favourable cases, it does not ex- 

 of 33 cwt., the velocity of the rubbing ceed the fortieth part of the pressure or 

 surfaces four feet per second at the weight that occasions it." 

 greatest, and the length of surface rub- 

 bed over about 1 000 feet at a medium. 

 These experiments seem to confirm the 

 opinion, that friction is an uniform re- 

 sistance, at least, where the rubbing 



surface moves with a velocity of from 

 nine inches to four feet per second ; 

 and Mr. Southern concludes from them, 



A memoir by Coulomb, on the friction 

 of pivots, will be found in the Memoirs 

 of the French Academy for 1790. 



A very instructive digest of all that 

 has been done towards establishing a 

 theory of friction, will be found in ^the 

 second volume of Dr. Gregory's Treatise 

 on Mechanics. 



