 treatise in defence of the phlogistic
theory, was so fair-minded, that after his work had been translated
into French and published with comments, he acknowledged that the old
theory was dead, and that truth had conquered.

It will be interesting now to trace Cavendish’s part in developing
the history of the discovery of the constituents of air, and to note
his arguments in favour of the phlogistic theory. Although Cavendish
never publicly acknowledged its insufficiency, yet he had ceased to
occupy himself with chemical problems at the time when its adoption was
universal, and his true opinions have never been recorded.

[4] _Experiments and Observations on Different Kinds of Air_, vol. ii.
    By Joseph Priestley, LL.D., F.R.S. Second edition (1776), p. 29.

[5] _Chemical Treatise on Air and Fire_ (1777), § 3.

[6] _Loc. cit._ p. 46.

[7] _Loc. cit._ p. 55.

[8] _Loc. cit._ p. 94.

[9] _Loc. cit._ p. 102.

[10] The accurate translation of Scheele’s _Treatise_ published by the
     Alembic Club (William F. Clay, 1894) has been made use of here.

[11] § 4.

[12] § 5.

[13] § 16.

[14] § 16.

[15] § 22.

[16] § 23.

[17] § 24.

[18] § 29.

[19] § 80.

[20] § 87.

[21] § 93.

[22] This, as previously remarked, had already been noticed. In
Maquer’s _Élémens de Chymie-pratique_, published in 1752, a work which
ran through many editions, we read (p. 307): “There happens during all
these calcinations, and especially in that of lead, a very strange
phenomenon for which it is very difficult to assign a reason. It is
that those bodies, which lose no small proportion of their substance,
whether by the dissipation of phlogiston, or because part of the
metal is exhaled as vapour, yield _calces_ increased in weight after
calcination; and this increase is by no means inconsiderable....
Physicists and chemists have devised many ingenious systems to account
for this phenomenon, but no one of them is absolutely satisfactory. As
no well-established theory has been devised, we shall not undertake to
attempt an