2ga Dr. Pearson’s Experiments for 
vanced, many acids were demonstrably proved to consist of a 
peculiar basis, and respirable air ; and on the ground of analogy 
it was concluded, that all other acids were composed in a si- 
milar manner. Fixed air having been shewn, by Mr. Bew- 
ley, and by Bergman, to be an acid, of course its composition 
was considered, in the new system of chemistry, to be similar 
to that of all other acids. On examining facts already well 
ascertained, and by various experiments discovering others, no 
clear instance could be perceived of the formation of fixed air, 
but in those cases where charcoal was applied red hot to respir- 
able air. Mr. Lavoisier at last established this interesting fact, 
by a conclusive experiment, published in a volume of the Me- 
moirs of the Academy of Sciences in 1781, and in his Traite 
Elementaire in 1789, by which he demonstrated that charcoal of 
wood, except a minute portion of residue, as might reasonably 
be expected, combined with respirable air, and composed fixed 
air only. This is the date, therefore, of the discovery by syn- 
thesis, of the composition of fixed air ; or, as I would rather call 
it, with Mr. Lavoisier, carbonic acid. The proof by analysis, 
however, was required, to render the demonstration of the 
composition of this elastic fluid complete. The honour of the 
first analytical experiments on carbonic acid is due to Mr. 
Tennant, F. R. S. who, in a paper read to this Society, in 
March, 1791, and contained in volume LXXXI. of the Philo- 
sophical Transactions, asserted, that charcoal and phosphoric 
acid were produced by applying phosphorus to red hot marble ; 
from which he inferred, that the carbonic acid of the marble 
was decompounded. This decomposition, the ingenious author 
conceives to be effected by the united powers of affinity be- 
tween phosphorus and the respirable air of the carbonic acid 
