98 Anthracite Coal of Rhode-Island. 
The anthracite furnaces are liable to an inconvenience, 
which is easily prevented, if attended to in season. The 
semi-vitrified matter, composed of the impurities of the coal, 
and which forms the slag, accumulates by adhering to the 
fire-bricks,; with which, by partial fusion, it forms a firm une 
ion. It should be removed by the poker every morning, 
when the furnace is cleaned: it is easily done from day to 
day ; but if neg it increases to an inconvenient degree 
thickens the lining all around—narrows the place for fuel 
. Appendix, May 11, 1826. 
Ihave been just favoured with a copy of a memoir, by Mr: 
Mareys Bull, read before the American Philosophical Sociee 
ty of Phi ia, April 7, 1826—entitled : 
_ ** Experiments to detérmine the comparative quantities of 
Heat, evolved in the combustion of the principal varieties of 
result e of n 
evidently conducted with great care and skill. It is replete 
with interesting information, and is to be regarded as one of 
the most important contributions of science to the arts and to 
domestic economy, which has beer made for a long time in 
is country. It is worthy of being carefully studied, both by 
scientific and practical. men, and for the sake of the latter 
class, it might be well if any analysis of this elaborate and 
paper, presenting, in a lucid and concise form, the 
important its:which have been obtained by Mr. 
i——were prepared for extensive circulation. 
= Tcannot discover in the memoir of Mr. Bull any import- 
ant variations from the results which I have presented. 
Mr. Bull finds the. specific gravity of the anthracites con+ 
