142 EFFECTS of HEAT 



firft tolerable compreffion accomplifhed by a determinate force. 

 The pyrometer indicated 2 2 Q . 



This experiment was repeated the fame day, when a ftill 

 fmaller quantity of metal efcaped at the muzzle ; but the bar- 

 rel had given way below, in the manner of thofe that have 

 yielded for want of fufficient air. Even this refult was fatis- 

 factory, by mewing that a mechanical power, capable of for- 

 cing fome of the barrels, could now be commanded. The car- 

 bonate in the little tube had loft 20 per cent.; but part of it was 

 in a hard and firm ftate, efFervefcing to the laft. 



No. 2. — On the 21ft June, I made an experiment with ano- 

 ther barrel, with the fame circumftances. I had left an empty 

 fpace in the large tube, and had intended to introduce its 

 muzzle downwards, meaning that fpace to.anfwer as an air- 

 tube j but it was inverted by miftake, and the tube entering 

 with its muzzle upwards, the empty fpace had of courfe filled 

 with metal, and thus the experiment was made without any 

 included air. There was no pyrometer ufed 5 but the heat was 

 guefTed to be about 25 ° where, the fubject of experiment 

 lay. The barrel, when opened, was found full of metal, 

 and the cradle being laid flat on the table, a confiderable 

 quantity of metal ran from it, which had undoubtedly 

 been lodged in the vacuity of the large tube. When cold, I 

 found that vacuity ftill empty, with a plating of metal. 

 The tube was very clean to appearance, and, when fhaken, 

 its contents were heard to rattle. Above the little tube, 

 and the cylinder of chalk, I had put fome borax and fand, 

 with a little pure borax in the middle, and chalk over it. 

 The metal had not penetrated beyond the borax and fand, by 

 a good fortune peculiar to this experiment ; the intrufion of 

 metal in this mode of execution, being extremely troublefome. 

 The button of chalk, was found in a ftate of clean white car- 

 bonate, and pretty hard, but without tranfparency. The little 



tube 



