' MODIFIED by COMPRESSION. 115 



bonate, the fubjec~t of experiment feldom weighing more than 

 10 or* 1 2 grains, and in others far lefs *. 



On the nth of April 1803, with a barrel of old fable 

 iron having a bore of 0.75 of an inch, I made an experi- 

 ment in which all thefe arrangements were put in prac- 

 tice. The large tube contained two fmall ones \ one filled 

 with fpar, and the other with chalk. I conceived that 

 the heat had rifen to 33 °, or fomewhat higher. On melting 

 the metals, the cradle was thrown out with considerable 

 violence. The pyrometer, which, in this experiment, had 

 been placed within the barrel, to my aftonifhment, indi- 

 cated 64 . Yet all was found. The two little tubes came 

 out quite clean and uncontaminated. The fpar had loft 

 17.0 per cent. : The chalk 10.7 per cent. : The fpar was 

 half funk down, and run againft the fide of the little 

 tube : Its furface was mining, its texture fpongy, and it was 

 compofed of a tranfparent and jelly-like fubftance : The chalk 

 was entirely in a ftate of froth. This experiment extends our 

 power of action, by fhewing, that compreffion, to a confider- 

 able degree, can be carried on in fo great a heat as 64 °. It 

 feems likewife to prove, that, in fome of the late experiments 

 with the fquare barrel, the heat had been much higher than 

 was fuppofed at the time, from the indication of the pyrometer 

 placed on the breech of the barrel ; and that in fome of them, 

 particularly in the lafl, it mull have rifen at leaft as high 

 as in the prefent experiment. 



P 2 On 



* I meafured the capacity of the air-tubes by means of granulated tin, acting 

 as a fine and equal fand. By comparing the weight of this tin with an equal 

 bulk of water, I found that a cubic inch of it weighed 1330.6 grains, and that 

 each grain of it correfponded to 0.00075 of a cubic inch. From thefe data I was. 

 able, with tolerable accuracy, to gage a tube by weighing the tin required to fiil 

 it. 



