18 



ACTION OF HEAT MODIFIED 



feebly agglutinated, but the chalk was in a state of firm lime- 

 stone, though it must have undergone a heat under 22°, or 

 that of melting silver. This experiment is certainly a most 

 remarkable one, since a heat has been applied, in which the 

 chalk has been changed to a hard limestone, with a loss less 

 than the lOOOdth part of its weight, (exactly -ttst); ^vhile, 

 under the same circumstances of pressure, though probably 

 with more heat, some of the same substance had been brought 

 to fusion. What loss of weight this fused part sustained, can- 

 not be known. 



Similnrcxperi- Qii the 4tb of January^ a similar experiment was made, 

 likewise with l.l grain of water. The discharge of the metal 

 was accompanied with a flash of flame. The pyrometer indi- 

 cated 26". The little tube came out quite clean. Its con- 

 tents had been reduced from 14.53 to 14.46, difference 0.0/ 

 grains, being 0.47 P^y cent, on the original carbonate, les9 

 than one two-hundredth part of the original vieight, (exactly 

 _.i._.). The chalk was in a state of firm saline marble, buS 

 with ho unusual qualities. 



The rarbonate These two last experiments are rendered still more intcrest- 

 * ing, by another set which I made soon after, which shewed,, 

 that one essential precaution in a point of such nicety had been 

 neglected, in not previously drying the carbonate. In several 

 trials made in the latter end of the same month, I found, that 

 chalk exposed to a beat above that of boiling water, but quite 

 short of redness, lost 0.34 per cent. ; and in another similar 

 trial, 0.46' per cent. Now, this ]oss of weight equals within 

 0.01 per cent, the loss in the last-mentioned experiment, that 

 being 0.47 ; and far surpasses that of the last but one, whicji 

 was but 0.074. There is good reason, therefore, to believe, 

 that had the carbonate, in these two last experiments, been 

 previously dried, it would have been found during compression 

 to have undergone no loss, 



Explanation of I'^e result of many of the experiments latel}' mentioned, 



some apparent gcems fully to explain the perplexing discordance between my 

 anomalies. . •' . / , . , , , , . 



experiments wan porceiani tuoes, and those made in barrels- 



of iron. Wilh the porcelain tubes, I never could succeed in 3. 



heat a'uove 28°, cr even quite up to it; yet the re-ults were 



often excellent. Whereas, the iron-barrels have currently 



stood iirm in heats of 4i° or 51°, and have reached even to 70* 



