for carbon and hydrogen. On the other hand, when the heating power of
coal low in hydrogen is determined by Thompson's calorimeter, much
difficulty is experienced in burning the carbon completely; hence a low
result is obtained. From a large number of experiments I have found that
when a coal does not yield more than 86 per cent, of coke, it gives its
full comparative heating power, but it is very questionable if equal
results will be worked out if the coke exceeds the above amount although
I have met with coals giving 87 per cent. of coke which were perfectly
manageable, though in other cases the coal did not burn completely. It
will be noted that the non-volatile residue of anthracite is never as
low as 86 per cent., and this, together with the very dry steam coals
and bastard anthracite (found over a not inextensive tract of the South
Wales Coal field), form a series of coals, alike difficult to burn in
Thompson's calorimeter. Considerable experience has shown that in no
single instance was the true comparative heating power of anthracite
or bastard anthracite indicated. With a view to accelerate the perfect
combustion of these coals, sugar, starch, bitumen, and bituminous
coals--substances rich in hydrogen--were employed, mixed in varying
proportions with the anthracitic coal, but without the anticipated
effect. Coke was also treated in a like manner. Without enlarging
further upon these futile trials--all carefully and repeatedly
verified--the results of my experiments and experience show that for
coals of an anthracitic character, yielding more than 87 per cent. of
coke, or for coke itself, Thompson's calorimeter is not suited as an
indicator of their comparative calorific power, for the simple reason
that some of the carbon is so graphitic in its nature that it will not
burn perfectly when mixed with nitrate and chlorate of potash. A sample
of very pure anthracite used in the experiments referred to, gave 90.4
per cent. of non-volatile residue, and only 0.84 per cent. of ash. This
coal was not difficult to experiment with, as combustion started with