into account at all. In the first place, hydrogen consumes only one
quarter as much oxygen as carbon, and, furthermore, two-ninths only of
the heating power of hydrogen is used as the multiplying number,
viz., 8,080, while the value of hydrogen is 34,462. In other words,
one-eighteenth only of the available hydrogen present in the fuel is
shown in the result obtained. Apart from this my experience of the
working of Berthier's method has been by no means satisfactory. There
is considerable difficulty in obtaining pure litharge, and it is almost
impossible to procure a crucible which does not exert a reducing action
upon the lead oxide. Some twelve months ago I went out to Italy to test
a large number of cargoes of coal with Thompson's calorimeter, and since
then this apparatus has superseded Berthier's process, and is likely to
come into more general use. Like Berthier's method, Thompson's apparatus
is not without its disadvantages, and the purpose of this paper is to
set these forth, as well as to suggest a uniform method of working by
means of which the great and irreconcilable differences in the results
obtained by some chemists might be overcome. It has already been
observed that a coal rich in hydrogen shows a low heating power by
Berthier's method, and it will become evident on further reflection that
the higher the percentage of carbon the greater will be the indicated
calorific power. In fact a good sample of anthracite will give higher
results than any other class of coal by Berthier's process. With
Thompson's calorimeter the reverse is the case, as the whole of the
heating power of the hydrogen is taken into account. In short, with
careful working, the more bituminous a coal is the more certain is it
that its full heating power shall be exerted and recorded, so far as the
apparatus is capable of indicating it; for when the result obtained is
multiplied by the equivalent of the latent heat of steam the product is
always below the theoretical heat units calculated from the chemical
composition of the coal by the acid of Favre and Silbermann's figures