for mcafuring the higher Degrees of Heat t &c. 
APPENDIX. 
ANALYSIS OF THE CLAY OF WHICH THE THERMOMETRIC 
PIECES ARE FORMED. 
THIS clay makes no eftervefcence with acids. Diluted ni- 
trous and marine acids being boiled upon it, and afterwards 
faturated with fixed alkali, no precipitation or turbidnefs ap- 
peared. It therefore contains no calcareous earth, as that earth 
would have been diflolved by the acids, and precipitated from 
them by the alkali. 
Calcined with powdered charcoal, it contracted no iul- 
phureous fmell, and the acids had no more action upon it than 
before. It therefore contains no gypfeous matter, or combi- 
nation of calcareous earth with vitriolic acid; as that acid 
would have formed fulphur with the inflammable principle of 
the charcoal, and left the calcareous earth pure, or in a ftate 
of folubilityby acids. 
Some of the clay was calcined with an equal weight of fait 
of tartar, which, for the greater certainty in regard to its 
purity, had been run per deliquium , and afterwards evaporated 
to drynefs. The calcined mixture was boiled in water, the 
filtered liquor {lowly evaporated, and buffered to cool at inter- 
vals. No cryftallization was formed : the dry fait appeared 
merely alkaline as at firff, and deliquiated in the air ; a further 
proof that this clay contains no gypfeous matter ; for the vitri- 
olic acid would have been abforbed by the alkali, and formed 
vitriolated tartar, a fiilt which neither liquefies in the air, 
U u 2 nor 
