]|g ACTIOIT or HEAt M0151FI"ED 



Lcat ofS^^vns appVkdj a loss took place of 13* per Cfwf. 

 All the original form had disappeared, the carbonate lying in 

 the cup as a complete liquid, with a concave surface, which 

 did not shine, but was studded all over with the white spheri- 

 cles or tufts, like those seen in the former results, without 

 any space between them. When detached from the cup, the 

 surface moulded on the platina, was white and pearly, with a 

 slight gloss. The mass was quite solid 5 no vestige whatever 

 appearing, of tlie original form of the fagments, (fig. 33.). 

 A small piece, broken off near the apex of the cone, shewed 

 the internal structure to be quite saline. In the act of ar-r 

 ranging the specimen on its stand, another piece came off in 

 a new direction, wtiich presented to view the most perfect 

 crystalline arrangement : the shiniag plane extended across 

 the whole specimen, and was more than the tenth of an inch 

 hi all directions. This fracture, likewise, shewed the entire 

 internal solidity of the mass. Unfortunately, this specimen 

 has suffered much by the same decay to which all of them 

 are subject which have lost any considerable weight. The 

 part next the outward surface alone remains entire. I have 

 never been able to explain, in a satisfactory manner, this dif^ 

 ference of durability ; the last-mentioned result having lost 

 more in proportion to its weight than this. 

 Artjfklal inne About the beginning of June, I received from Mr. Hatch- 



caibonate of ^^^ some pure carbonate of lime, which he was so orood as to. 



lime from Mr. ' , , . . , » , 



Hatchett. It prepare, with a View to my experiments ; and I have been con-. 



Resisted the stantly employed with it till within these few days. 



touch- My first experiments with this substance were peculiarly 



unfortunate, and it seemed to be less easily acted upon than 

 any substance of the kind I had tried. Its extreme purity, 

 no doubt, contributed much to this, thoii^h another circum- 

 stance had likewise had some effect. The powder, owing (© 

 a crystallization which had taken place on its precipitation, 

 was very coarse, and little susceptible of close ramming ; the 

 particles, therefore, had less advantage than wiien a line 

 powder is used, in acting upon each otlier, and I did not 

 choose to run any risk of contamination, by reducing the 

 substance to a finer powder. Whatever be the cause, it is 



— w-ns ch.nTigifl certain, that in many experiments in which the chalk was 



!iito maiblf-, changed to marble, this substance remained in a loose and 



brittle 



