Anthracite formation of Wilkesbarre, &c. 7 
ter, dropping in each two long semicircular wedges, the 
thick end of each down, and driving in a long very gradually 
tapering wedge between them, so that the greatest pressure 
shall act at bottom. These wedges are alternately driven, 
until a large mass of the coal breaks off, when it is broken 
up with sledges, of a convenient size for handling. Gun- 
powder is occasionally used, but the effect is much less 
certain than that of the drill and wedges. 
The specific gravity of our best coal, is from 1-5 to 1-6. 
The purer the coal the less is its specific gravity. In its 
purest state, the fracture is what the German mineralogists 
would term muschliger, that is of a conchoidal splintery 
fracture breaking like rosin. This is its true fracture ; 
but when contaminated with slate, or pervaded by delicate 
layers of it, even imperceptibly so, its fracture becomes 
more angular, lamellar and cubical—in the former state, it 
affords but a small quantity of ashes, in the latter the quan- 
tity is considerable. 
In the samples, the pure is marked No. 7, the impure 8. 
Brilliant specimens of pavonine, or iridescent coal, are 
abundant; but this kind is found only in the water, or in 
moist situations. 
Our anthracite, when pure, affords the most intense heat 
of any of the carbonaceous minerals. In a properly con- 
structed wind furnace, of the cubic dimensions of ten or 
twelve inches, cast iron readily melts, and the most refrac- 
tory clays, either become glazed, melt, or loose their form. 
The best Spring-Cove and New-Castle Delaware clay, used 
for glass pots in this country, which will stand the heat of a 
window glass furnace, for six or eight weeks, will melt in 
thirty minutes ; and feldspar, in a few minutes, is changed 
io a porcelain. Water thrown on it is instantly decomposed. 
I am, sir, very respectfully, 
ZACHARIAH CIST. 
Wilkesbarre, Pennsylvania, July 2, 1821. 
Practical facts relating to the Lehigh or Wilkesbarre coal, 
cited principally from the pamphlet mentioned in the letter 
of Mr. Cist to the Editor. 
1 
[This pamphlet appears to have been published about 
six years ago, and although written evidently not with 
