' MODIFIED by COMPRESSION. - 115 
* bonate, the fubject of experiment, feldom weighing more than 
10 or’12 grains, and in others far lefs * 
On the rrth of April 1803, ite 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 finall ones ; one filled 
with {par, 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 confiderable 
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 {par had loft 
17.0 per cent.: The chalk 10.7 per cent.: The {par was 
half funk down, and run againft the fide of the little 
tube: Its furface was fhining, 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 laft, it muft have rifen at leaft as high 
as in the prefent experiment. 
TSK Pa On 
* I meafured the capacity of the air-tubes by means of granulated tin, ating 
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 cerrefponded to 0.00075 of a cubic inch. From thefe data 1 was - 
able, prin tolerable accuracy, to gage a tube by weighing the tin required to fiil 
it. 
