// ntf the Confequenet if Change of Capaeity, 1 05 



The folld contents of this hollow cylinder, exclufive of the cylindrical neck by which it 

 remained united to the cannon, were 385+- cubic inches, Englifh meafure, and it weighed 

 1 1 3. 13 lb. avoirdupois, as I found on weighing it at the end of the courfe of experiments 

 made with it, and after it had been feparated from the cannon with which, during the 

 experiments, it remained conneQed *. 



Experiment No. I. 



THIS experiment was made in order to afcertain how much heat was adtually gene- 

 rated by fridtion, when a blunt fteel borer being fo forcibly fhoved (by means of a ftrong 

 fcrew) againft the bottom of the bore of the cylinder, that the preflure againft it was equal 

 to the weight of about 1 0,000 lb. avoirdupois, the cylinder was turned round on its axis 

 (by the force of horfes) at the rate of about 32 times in a minute. 



This machinery, as it was put together for the experiment, is reprefented by fig. 2. 

 W is a ftrong horizontal iron bar connected with proper machinery carried round by 

 horfes, by means of which the cannon was made to turn round its axis. 



To prevent, as far as poITible, the lofs of any part of the heat that was generated in the 

 experiment, the cylinder was well covered up with a fit coating of thick and warm flannel, 

 which was carefully wrapped round it, and defended it on every fide fiom the cold air of 

 the atmofphere. This covering is not reprefented in the drawing of the apparatus, 

 fig. 2. 



I ought to mention, that the borer was a flat piece of hardened fteel, 0.63 of an. inch 

 thick, 4 inches long, and nearly as wide as the cavity of the bore of the cylinder, namely, 

 3f inches. Its corners were rounded off at its end, fo as to make it fit the hollow bottom 

 of the bore ; and it was firmly fattened to the iron bar (m), which kept it in its place. The 

 area of the furface, by which its end was in conta£l with the bottom of the bore of the 

 cylinder, was nearly 2^ inches. This borer, which is diftinguiftied by the letter n, is re- 

 prefented in moft of the figures. 



At the beginning of the experiment, the temperature of the air in the fhade, as alfo 

 that of the cylinder, was juft 60° F. 



At the end of 30 minutes, when the cylinder had made 960 revolutions about its axis, 

 the horfes being ftopped, a cylindrical mercurial thermometer, whofe bulb was -j^^ of an 

 inch in diameter, and 3^ inches in length, was introduced into the hole made to receive 

 it, ia the fide of the cylinder j when the mercury rofe inftantly to 130*. 



Though the heat could not be fuppofed to be quite equally diftributed in every part of 

 the cylinder, yet, as the length of the bulb of the thermometer was fuch that it extended 



* For fear T fliould be fvifpe£led of prodigality in the profeciiticn of my philofophical rcfuarches, I think it 

 jieccffary to ijiform the Society, that the cannon I made ufe of in this experiment was not facrificed to ir. 

 The fliort hollow cylinder which was formed at the end of it, was turned out of a cylindrical mafs of metal 

 about two feet in length, projefting beyond the muzzle of the gun, called in the German language the verj- 

 lorncr kopf, (the head of the cannon to be thrown away,) and which is reprefented in fig. i. 



This additional projeftion, which is cut off before the gun is bored, is always caft with it, in order that, by 

 means of th« preffure of its weight on the metal in the lower part of the mould, daring the time it is cooling-, 

 the gun may be the more compaft in the neighbourhood of the muzzle, where, without thij precaution, the 

 Bwul would be apt to be porous or full of honeycombs, 



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