Count Rum ford's Inquiry concerning 
removed ; and the borer being taken out of the cylinder, 
the scaly metallic powder, which had been produced by the 
friction of the borer against the bottom of the cylinder, was 
collected, and, being carefully weighed, was found to weigh 
4145 grains, or about 8f oz. Troy. 
As this quantity was produced in 2^ hours, this gives 824 
grains for the quantity produced in half an hour . 
In the first experiment, which lasted only half an hour , the 
quantity produced was 837 grains. 
In the experiment No. 1, 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 degrees, 
or cause it to boil. 
According to the result of the experiment No. 3, the heat 
generated in half an hour, would have caused 5.311b. of ice-cold 
water to boil. But, in this last-mentioned experiment, the heat 
generated being more effectually confined, less of it was lost ; 
which accounts for the difference of the results of the two ex- 
periments. 
It remains for me to give an account of one experiment 
more, which was made with this apparatus. I found by the 
experiment No. 1. how much heat was generated when the 
air had free access to the metallic surfaces which were rubbed 
together. By the experiment No. 2, I found that the quan- 
tity of heat generated was not sensibly diminished when the 
free access of the air was prevented; and, by the result of 
No. 3, it appeared that the generation of the heat was not 
prevented, or retarded, by keeping the apparatus immersed in 
water. But as, in this last-mentioned experiment, the water, 
though it surrounded the hollow metallic cylinder on every 
