the chapter.
The errata listed at the end of the book have been corrected in the
text. In the text, there are places where the apothecary symbols for
ounce and dram are used. These are changed to oz. and dr. in the text
file.

THE PREFACE.

One reason for the present publication has been the favourable reception
of those of my _Observations on different kinds of air_, which were
published in the Philosophical Transactions for the year 1772, and the
demand for them by persons who did not chuse, for the sake of those
papers only, to purchase the whole volume in which they were contained.
Another motive was the _additions_ to my observations on this subject,
in consequence of which my papers grew too large for such a publication
as the _Philosophical Transactions_.

Contrary, therefore, to my intention, expressed Philosophical
Transactions, vol. 64. p. 90, but with the approbation of the President,
and of my friends in the society, I have determined to send them no
more papers for the present on this subject, but to make a separate and
immediate publication of all that I have done with respect to it.

Besides, considering the attention which, I am informed, is now given to
this subject by philosophers in all parts of Europe, and the rapid
progress that has already been made, and may be expected to be made in
this branch of knowledge, all unnecessary delays in the publication of
experiments relating to it are peculiarly unjustifiable.

When, for the sake of a little more reputation, men can keep brooding
over a new fact, in the discovery of which they might, possibly, have
very little real merit, till they think they can astonish the world with
a system as complete as it is new, and give mankind a prodigious idea of
their judgment and penetration; they are justly punished for their
ingratitude to the fountain of all knowledge, and for their want of a
genuine love of science and of mankind, in finding their boasted
discoveries anticipated, and the field of honest fame pre-occupied, by
men, who, from a natural ardour of mind, engage in philosophical
pursuits, and with an ingenuous simplicity immediately communicate to
others whatever occurs to them in their inquiries.

As to myself, I find it absolutely impossible to produce a work on this
subject that shall be any thing like _complete_. My first publication I
acknowledged to be very imperfect, and the present, I am as ready to
acknowledge, is still more so. B