10« 



Eri^ECtS 0¥ HEAT. 





--•being Iff* 

 fufible, &c. 



An apparatus 

 refembling that 

 of Count Rum- 

 ford, 



•-^and regulated 



PrcfTure 3 or 

 ^ hundred at- 

 mofpheres. 



Similar experi- 

 ments on bitu- 

 minous matter. 



fuccefs. But thefe have frequently been of value, by bring* 

 ing into view important collateral fa6ls. Thus I have found 

 that under certain circumftances, a partial calcination has taken 

 place by the feparation of forae of the carbonic acid from the 

 lime, though enough ftill remained to preferve many of the 

 Jeading properties of a carbonate. When a lofs is fuftained, 

 amounling only to two or three, or even four per cent, I find 

 the fubllance ftill fufceptible of agglutination and fulion, but 

 its fufibility is greatly diminiilied, a heat of 40 or 50 being re* 

 quired to accomplifli what would have been done in 22 or 25, 

 had the earth continued to be completely faturated with car- 

 bonic acid, and the carbonate thus obtained is apt to fall to 

 decay by attra6ling moiflure from the air. Thefe differences 

 afford a good illuflration of the influence exerted by the acid as 

 ^ flux on the earth. 



Having thus afcertained the fufibility of the carbonate under 

 prelfgre of indefinite amount, I became defirous of affigning 

 its limits, and of difcovering the leaft force neceffary for this 

 purpofe. In this view, in addition to my other devices, I fol- 

 lowed thofe ufed by Count Rumford in trying the explofive 

 flrength of gun-powder.* 



By means of a great w^eight prefling upon a fmall opening, 

 and regulated by a counterpoife adjufted at pleafure, I was able 

 to conftrain the carbonate to any given amount. In this man- 

 ner I found that the preflTure of 80 atmofpheres, anfwering 

 nearly to half a mile of fea in depth, was requifite to produce 

 any etfe6l of compreflion on the carbonate of lime, and that 

 to execute the bufinefs vv'ell required a force four or five times 

 greater. 



I have likewife made fome experiments with coal treated in 

 the fame manner as the carbonate of lime, but I have found it 

 much lefs tractable, for the bitumen, when heat is applied to 

 it, tends to efcape by its fimple elaflicity, whereas the carbo- 

 nic acid in marble is in part retained by the chemical force of 

 quick lime. | fucceeded, however in conftraining the bitu- 

 nienous matter of the coal to a certain degree in red heats, fo 

 as to bring the fubllance into a complete fufion, and to retain 

 its faculty of burning with flame. But I could not accomplifli 

 this in heats capable of agglutinating the carbonate; fori have 

 fpiind, vyhere I rammed them fucceflfively into the fame tube, 



* Philof. Journal, quarto feries, I. 45?» 



an4 

 4- 



