Heat excited in boring Cannon> - -tpj 



■yery Interefting philofopliical experiments might often be made, almoft without troubie»-o^ 

 -expence, by means of machinery contrived for the mere mechanical purpofes of the arts and 

 manufactures. 



I have frequently had occafion to make this obfervation ; and am perfuaded, that a habit 

 of keeping the eyes open to every thing that is going on in the ordinary courfe of the bufi- 

 nefs of Hfe, has oftener led, as it were by accident, or, in the playful excurfions of the ima- 

 gination put into aftion by contemplating the moft common appearances, to ufeful doubts 

 and ferviceable fchemes for inveftigation and improvement, than all the more intenfe me- 

 ditations of philofophers in the hours cxprefsly fet apart for ftudy. 



It was by accident that I was led to make the experiments of which I am about to give 

 an account ; and though they are not, perhaps, of fuflicient importance to merit fo formal 

 an introdudlion, I cannot help flattering myfelf that they will be thought curious in feveral 

 refpefls, and worthy of the honour of being made known to the Royal Society. 

 ' Being engaged, lately, in fuperintending the boring of cannon in the workfliops of the 

 military arfenal at Munich, I was ftruck with the very confiderable degree of heat which a 

 •brafs gun acquires in a (liort time in being bored, and with the more intenfe heat (much* 

 greater than that of boiling water, as I found by experimerit) of the metallic chips feparated 

 from it by the borer. 



The more I meditated on thefe phenomena, the more they appeared to me to be curious 

 and intercfling. A thorough invedigation of them feemed even to bid fair to give a farther 

 infight into the hidden nature of heat ; and to enable us to form fome reafonable conjeflures 

 refpefling the exiftence or non-exiftence of an igneous Jluid : a fubjecSl on which the opinions 

 of philofophers have in all ages been much divided. 



In order that the Society may have clear and diftin£l: ideas of the fpeculations and reafon- 

 ings to which thefe appearances gave rife In my mind, and alfo of the fpecific objects of 

 philofophical invedigation they fuggefted to me, I mufl: beg leave to (late them at fom^ 

 length, and in fuch manner as I fliall think bed fuitcd to aiifwer this purpofe. 



From whence cemej the heat adlually produced in the mechanical operation above men- 

 tioned ? 



Is it fumllhed by the metallic chips, which are feparated by the borer from the folid 

 jn^fs of metal ? ^ 



If this were the cafe, then, according to the modern dotlrines of latent heat and of calo,?,, 

 ric, the capacity for heat of the parts of the metal fo reduced to chips, ought not only to be 

 changed, but the change undergone by them (liould be fufBciently great to account for all 

 the heat produced. 



But no fuch change had taken place; for I found, upon taking equal quantities by 

 ■weight of thefe chips, and of thin flips of the fame block of metal, feparated by means of 

 a fine faw, and putting them at the fame temperature (that of boiling water) into equal 

 <juantities of cold water (that is to fay, at the temperature of 59!*' F.), the portion of water 

 into which the chips were put was not, to all appearance, heated either lefs or more thaa 

 the other portion into which the flips of metal were put. 



■ This experiment beingrejieated feveral times, the refalts were always fo nearly the fame, 



P 2 ■ that 



