132 Mr. Hatchett’s Experiments on a Substance, 
equal quantities of those substances are exposed to simple 
distillation. 
For, (as I have stated in my first Paper,) 100 grains of 
common resin by the humid process afforded 43 of coal, which 
after a red heat still weighed 30 grains. 
But the same quantity of resin by distillation, only yielded 
\ of a grain of coal. 
100 grains of mastich, by the first method, afforded 66 
grains of coal. 
100 grains of the same mastich only gave 4^- grains of coal 
when simply distilled. 
And 100 grains of amber, when treated with sulphuric acid, 
yielded 5b grains of coal. 
But from 100 grains of the same amber when distilled, 
only 32- grains could be obtained. 
Many other examples might be adduced, but these appear 
to be sufficient ; and I must here observe, that the case is 
very different in respect to the gums, for the difference 
between the proportions of coal obtained from them by the 
humid and dry ways is not very considerable, although it is 
always the greatest in the former process, when conducted 
with precaution. Moreover it is to be remarked, that in 
either process, variations in the quantity of coal are produced 
by difference of temperature, by the figure and size of the 
vessels, and many other circumstances. 
But it is not only in the proportion, that there is so great 
a difference between the coal obtained from the resinous sub- 
stances by the humid way or by fire, for the quality is also 
most commonly different ; and this not only applies to the 
resins but also to ligneous matter. 
