Life of Count Rumford. 477 



cylinder is made longer than the intended cannon, a 

 projection nearly ten inches beyond what will be the 

 muzzle of the completed weapon forming part of the 

 contents of the mould. The object of this additional 

 material is, that by the pressure of its weight on the 

 metal below it in the mould, while it is cooling, the 

 gun may be more compact in the neighborhood of the 

 muzzle, when, without this precaution, the metal there 

 would be likely to be porous or honeycombed. Tak- 

 ing a brass six-pounder cast solid, and rough from the 

 foundry, he had it finished by the usual process of turn- 

 ing. He then cut round the projection beyond the 

 muzzle, leaving it attached only by a small cylindrical 

 neck to the intended muzzle. This short cylinder, sup- 

 ported horizontally, and still united to the cannon, was 

 bored, in the usual way, to a depth which left to it a 

 solid bottom two and six tenths inches in thickness. 

 Intending to use this cylinder for the purpose of gene- 

 rating heat by friction, a blunt borer of hardened steel 

 was pressed against the bottom of the cavity in it by a 

 force of ten thousand pounds, while the cannon to 

 which the cylinder was attached was made to revolve by 

 horse-power at the rate of thirty-two times a minute. In 

 order that he might measure the heat that accumulated 

 in the cylinder, he introduced into i-t a small cylindrical 

 mercurial thermometer, through a round hole, drilled 

 perpendicularly to the axis of the cylinder, thirty-seven 

 hundredths of an inch in diameter, and four and two 

 tenths inches in depth. This hole ended in the middle 

 of the solid part of the metal which formed the bottom 

 of its bore. The object of this first experiment was to 

 ascertain how much heat was actually generated by fric- 

 tion under these given conditions, the pressure of a 



