108 Experiments to Jhew thai Heat excited iy Friliion 



that I could not determine whether any, or what change had been produced In the metaly 

 in regard to its capacity for heat, by being reduced to chips by the borer*. 



From hence it is evident, that the heat produced could not poflibly have been furnifhed 

 at the expence of the latent heat of the metallic chips. But, not being willing to reft fatif- 

 fied with thefe trials, however conclufive they appeared to me to be, I had recourfe to the 

 following dill more decifive experiment. 



Taking a cannon (a brafs fix pounder) caft folid, and rough as it came from the foun- 

 dry, (fee fig. I, plate V) and fixing it (horizontally) in the machine ufed for boring, and at 

 the fame time finifhing the outfide of the cannon by turning, (fee fig. 2.) I caufed its ex- 

 tremity to be cut ofF, and, by turning down the metal in that part, a folid cylinder was 

 formed, 7f inches in diameter, and 9 ?^ inches long ; which, when finiflied, remained joined 

 to the reft of the metal (that which, properly fpeaking, conftituted the cannon,) by a fmall 

 cylindrical neck, only ^\ inches in diameter, and ^-rs inches long. 



This ftiort cylinder, which was fupported in its horizontal pofuion,and turned round its 

 axis, by means of the neck by which it remained united to the cannon, was now bored with, 

 the horizontal borer ufed in boring cannon ; but its bore, which was 3.7 inches in diameter, 

 inftead of being continued through its whole length, (9.8 inches) was only 7.2 inches in 

 length; fo that a folid bottom was left to this hollow cylinder, which bottom was 2.<S 

 inches in thicknefs. 



This cavity is reprefented by dotted lines in fig. 2 ; as alfo In fig. 3, where the cylinder is 

 reprefented on an enlarged fcale. 



This cylinder being defigned for the exprefs purpofe of generating heat by friftion, by 

 having a blunt borer forced againft its folid bottom at the fame time that it Ihouldbe turned, 

 round its axis by the force of horfes, in order that the heat accumulated in the cylinder 

 might from time to time be meafured, a fmall round hole, (fee d, e, fig. 3.) 0.37 of an inch 

 only in diameter, and 4.2 inches in depth, for the purpofe of introducing a fmall cylindrical 

 mercurial thermometer, was made in it, on one fide, in a direflion perpendicular to the axis, 

 of the cylinder, and ending in the middle of the folid part of the metal which formed the 

 bottom of its bore. 



* As thefe experiments are important, it may, perhaps, be agreeable to the Society to be mad« acquainted 

 yith them in their deiails. One of them was as follows i 



To 4590 grains of water, at the temperature of 59^*?". (an allowance or compenfation, reckoned in waterj 

 for the capacity for heat of the containing cylindrical tin velTel, being included) were added ioi6i grains of 

 gun-metal in thin flips, feparated from the gun by means of a fine faw, being at the temperature of 210° F. 

 When they had remained together 1 minute, and had been well ftirpcd about by meant of a fmall rod of light- 

 wood, the heat of the mixture was found to be z=. 63°. 



From this experiment, the fpecific heat of the metal, calculated according to the rule given by Dr. Crawford, 

 turns out to be =: o.iioo, that of water being = i.ooo. 



An experiment was afterwards made with the mctalUc chips, as follows : 

 ' To the fame quantity of water as was ufed' in the experiment above mentioned, at the fame temperature, 

 (viz. 59i°,) and in the fame cylindrical tin veffel, were now put ioi6j- grains of metallic chips of gun-metal, 

 bored out of the fame gun from which the flips ufed in the foregoing experiment were taken, and at the fame 

 temperature (zio°.) The heat of the mixture, at the end of i minute, was juft 63°, as before; confequemly 

 the fpecific heat of thefe metallic chips was = o.noQ. Each of the above eXperimeius was repeated three 

 liaiM, and ahvays with nearly the fame refultt. 



The 



