Expenmenis on the Heat excited by FrlBien. T 1-5 



But no circumftances can be imagined in which this method of procuring heat would not 

 be difadvantageous ; for more heat might be obtained by ufing the fodder ncceflary for the 

 fupport of a horfe as fuel. 



As foon as the laft-mentloned experiment (No. 3 ) was finilhed, the water in the wooden 

 box was let off, and the box re.moved ; and the borer being taken out of the cylinder, 

 the fcaly metallic powder, which had been produced by the fridtion of the borer againft the 

 bottom of the cylinder, was col!e£led, and, being carefully weighed, was found to weigh 

 4145 grains, or about 8y oz. troy. 



As this quantity was produced in 2| hours, this gives 830 grains for the quantity pro- 

 duced in half an hour. 



In the firft experiment, which lulled only half an hour, the quantity produced was 837 

 grains. 



In the experiment No. i, the quantity of heat generated in half an hour was found to be 

 equal to that which would be required to heat 51b. avoirdupois of ice-cold water 180 de- 

 grees, or caufe it to boil. 



According to the refult of the experiment No. 3, the heat generated in half an hour 

 would have caufed 5.311b. of ice-cold water to boil. But in this lad-mentioned experiment, 

 the heat generated being more efFedlually confined, lefs of it was loft ; which accounts for 

 the difference of the refults of the two experiments. 



It remains for me to give an account of one more experiment which was made with this 

 apparatus. 1 found, by the experiment No. i, how much heat was generated when the air 

 had free accefs to the metallic furfaces which were rubbed together. By the experiment 

 No. 2, I found that the quantities of heat generated were not fenfibly diminifhed when the 

 free accefs of the air was prevented ; and, by the refult of No. 3, it appeared that the 

 generation of heat was not prevented or retarded by keeping the apparatus immerfed in wa- 

 ter. But as, in this laft-mentioned experiment, the water, though it furrounded the hollow 

 metallic cylinder on every fide, externally, was not fuftered to enter the cavity of the bore 

 (being prevented by the piflon), and confequently did not come into conta£l with the metal- 

 lic furfaces where the heat was generated ; to fee what efFedls would be produced by giving 

 the water free accefs to thefe furfaces, I now made the 



Experiment Islo, 4« 



THE pifton which clofcd the end of the bore of the cylinder being removed, the blunt 

 borer and the cylinder were o-nc'e more put together ; and the box being fixed in its place, 

 and filled with water, the machinery was again put in motion. 



There was nothing in the refult of this experiment that renders it neceftary for me tq 

 be very particular in my account of it. Heat was generated as in the former experiments, 

 and to all appearance quite as rapidly ; and I have no doubt but the water in the box 

 would have been brought fo boil, had the experiment been continued as long as the laft. 

 Tlie only circumftance iliat furprifed n>e was, to find how little difference was occafioned 

 in the noife made by the borer in rubbing againft the bottom of the bore of the cyHnder, 

 by filling the bore with water. ^IThis noife, which was very grating to the ear, and fonie- 

 times almoft infupportable, was, as nearly as I could judge of it, quite as loud and as dif- 



,Qji agreeable 



