the Heat excited by Friction. 475 



from time to time be measured, a small round hole (see 

 d^ (?, Fig. 3), 0.37 of an inch only in diameter, and 4.2 

 inches in depth, for the purpose of introducing a small 

 cylindrical mercurial thermometer, was made in it, on one 

 side, in a direction perpendicular to the axis of the cylin- 

 der, and ending in the middle of the solid part of the 

 metal which formed the bottom of its bore. 



The solid contents of this hollow cylinder, exclusive 

 of the cylindrical neck by which it remained united to 

 the cannon, were 385! cubic inches, English measure, 

 and it weighed 1 13.13 lb., avoirdupois ; as I found on 

 weighing it at the end of the course of experiments made 

 with it, and after it had been separated from the cannon 

 with which, during the experiments, it remained con- 

 nected.* 



Experiment No. i. 



This experiment was made in order to ascertain how 

 much Heat was actually generated by friction, when a 

 blunt steel borer being so forcibly shoved (by means of 

 a strong screw) against the bottom of the bore of the 

 cylinder, that the pressure against it was equal to the 

 weight of about 10,000 lb., avoirdupois, the cylinder 



* For fear I should be suspected of prodigality in the prosecution of my philo- 

 sophical researches, I think it necessary to inform the Society that the cannon I made 

 use of in this experiment was not sacrificed to it. The short hollow cylinder which 

 was formed at the end of it was turned out of a cylindrical mass of metal, about 2. 

 feet in length, projecting beyond the muzzle of the gun, called in the German language 

 the •verlorner kopf (the head of the cannon to be thrown away), and which is repre- 

 sented in Fig I. 



This original projection, which is cut off before the gun is bored, is always cast 

 with it, in order that, by means of the pressure of its weight on the metal in the lower 

 part of the mould during the time it is cooling, the gun may be the more compact in 

 the neighbourhood of the muzzle, where, without this precaution, the metal would be 

 apt to be porous, or full of honeycombs. 



