334 Anthracite Coal of Pennsylvania. 
_ None of these varieties of coal would, before ignition, im- 
ss, but the Pennsylvania anthracites, after having 
ineined the heat of the furnace, became so hard that with 
an angular piece, 1 could write my name, on’green window 
glass, with a flourishing hand, much as with a piece of quartz. 
This is in accordance with what many persons have observed 
with respect to the effects of heat upon different varieties of 
eeivenks as in the: Surturbrand of lonlentiiers San of ubisp 
tained by Sir Humphrey Davy, with the great battery oF the 
Royal Institution, and those observed in the use of Dr. Hare’s 
instruments have been already described in this Journal. | 
Ihave often observed that well prepared charcoal, after very 
autins ignition, speedily spoils a knife, used in shaping at 
0 points, and even the best files do not long withstand its 
action, as their teeth are eventually worn down by the hard 
ey molecules of the charcoal. 
» T have observed also that.even the coak obtained by. igniting 
i bituminous coal rapidly destroyed the polish of glass, thus 
perenne upon its surface, the eflects of the gritty powders, 
in grinding a these e comme al ie 
the in dura 
See senor to , find that the naa sey both Bone the 
£ommon bituminous Liverpool coal, and from the Cannel coal, 
allowed me to write rapidly and distinctly with the pieces ape 
the hardest green window glass, and when two or three pant 
ignition, the bituminous coals should, in this respect, haye 
more remarka ably diminished. Perhaps a satisfactory sol 
aiticalty can he found in the fact that the anthracites, 
soft in the fire, 1 
ts, when suffering the aqueous 
ed water of erystallization. Thus the 
nce of pe of left 
“FY 
“si 
So nen ee 
