Intellisetice and Miscellaneous Articles. 



247 



ON THE EVOLUTION OF HEAT BY FRICTION AND PERCUSSION. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



To satisfy the inquiries of your Correspondent E., respecting the 

 evolution of heat from iron by percussion, I immersed a small rod 

 of iron in water contained in an iron basin, and struck it a few smart 

 blows with a hammer; the end of the rod became hot as readily, 

 though not so intensely, in water as in air. 



As I have thus easily answered your Correspondent's inquiry, 

 will you give me leave to inquire in your Philosophical work, first, 

 Whether the heat thus evolved by percussion is not always accom- 

 panied by a corresponding loss of cohesion in the metal acted 

 upon. 



Secondly, Whether annealing, which restores its cohesion, is not 

 simply restoring the heat evolved, or expressed from it by per- 

 cussion, which increasing the specific gravity of the metal, de- 

 creases its capacity for heat. 



Thirdly, Whether the great quantity of heat evolved by the fric- 

 tion of two metallic surfaces, under water, as observed by Count 

 Rumford, and under oil, as is frequent in heavy machinery, is not 

 strictly the effect of the destruction of cohesion, produced by abra- 

 sion; and whether heat is ever evolved under such circumstances, 

 unless cohesion is destroyed. 



August 13, 1832. X. 



LUNAR OCCULTATIONS FOR SEPTEMBER. 



Occnltations of Planets and fixed Stars by the Moon, in September 

 18S2. Computed for Greenwich, by Thomas Henderson, Esq. ; 

 and circulated by the Astronomical Society. 



* Immersion in horizon. 



