1G 
production of oxygen to Lavoisier before he had himself 
obtained it, which, however, does not appear probable, 
Lavoisier investigated its chief properties before Priest- 
ley knew any more of it, than it was a gas containing 
nitrous particles. ‘‘ Till this first of March, 1775,” writes 
Priestley, “‘ I had so little suspicion of the air from mer- 
curius calcinatus being wholesome, that I had not even 
thought of applying to it the test of nitrous air.” Again, 
in speaking of an experiment made on March 8, 1775, he 
says: “ By this I was confirmed in my conclusion that 
the air extracted from mercurius calcinatus, &c., was at 
least as good as common air ; but I did not certainly con- 
clude that it was any defter.” At this time Lavcisier had 
proved the principal properties of the new gas, as we 
now know them. No wonder he expresses surprise. 
Did Paracelsus discover hydrogen? or did Boyle? or 
Mayow? or Cavendish? Lavoisier saw with much sur- 
prise, not that a gas was produced by heating calx of 
mercury, but that the gas was different from fixed air. 
Let us finally examine Dr. Thomson’s criticism of the 
“ Opuscules Physiques et Chimiques” :— 
“ Nothing in these essays,” he writes, “indicates the 
smallest suspicion that air was a mixture of two distinct 
fluids, and that only one of them was concerned in com- 
bustion and calcination ; although this had been already 
deduced by Scheele from his own experiments, and 
though Priestley had already discovered the existence 
and peculiar properties of oxygen gas. It is obvious, 
however, that Lavoisier was on the way to make these 
discoveries, and had neither Scheele nor Priestley been 
fortunate enough to hit upon oxygen gas, it is exceedingly 
likely that he would himself have been able to have made 
that discovery.” 
Now these essays were published “az commencement 
de 1774,” at which time we have abundant evidence from 
other memoirs that Lavoisier 4ad more than suspicion 
“that air was a mixture of two distinct fluids, and that 
only one of them was concerned in combination and calci- 
nation.” Moreover, this had wot “been already deduced 
by Scheele from his own experiments; neither had 
Priestley ‘already discovered the existence and peculiar 
properties of oxygen gas.” 
We do not the least press the following point. We 
trust we have made out our case without the necessity of 
resorting to it ; but we venture toask upon what authority 
Dr. Thomson asserts that “ Dr. Priestley informs us that 
he prepared this gas in M. Lavoisier’s house in Paris, 
and showed him the method of procuring it in the year 
1774.” In our edition of Priestley’s works (3 vols. 8vo. 
“ Being the former six volumes abridged and methodised 
with many additions.” Birmingham: Thomas Pearson, 
1790), Priestley, after telling us that he visited Paris in 
Cctober, 1774, says, ‘‘I frequently mentioned my surprise 
at the kind of air which I had got from this preparation 
to M. Lavoisier, Mr. Le Roy, and several other philo- 
sophers, who honoured me with their notice in that city” 
(p. 109). And again, ‘“‘as I never make the least secret 
of anything I observe, I mentioned this experiment also, 
as well as those with the mercurius calcinatus, and the 
red precipitate to all my philosophical acquaintances at 
Paris and elsewhere; having no ideaat that time, to what 
these remarkable facts would lead.” It is of course a 
very different thing to mention an experiment to an ac- 
quaintance, and to actually perform it before him. But 
suppose, as Dr. Thomson asserts, that Priestley had pre- 
par.d the gas from mercurius calcinatus in Lavoisier’s 
house in October 1774, it is abundantly manifest by his 
own confession that he had no idea at that time of the 
nature of the gas; and more than five months afterwards 
that he had “so little suspicion of the air from mercurius 
calcinatus being wholesome, that I had not even thought 
ot applying to it the test of nitrous gas”; and even so late 
as March 8, 1775, he did not conclude that the new gas 
was any better than common air! 
NATURE 
[| Wov. 2, 132 
Who is the discoverer? Is it the man who obtains a 
new body for the first time without recognising that it is 
different from anything else, or is it the man who demon- 
strates its true nature and properties? If the former 
Eck de Sulzbach discovered oxygen in 1489, and Boyle in 
1672 not only procured hydrogen but proved its inflamma- 
bility. If the latter, assuredly Lavoisier discovered 
oxygen. 
But whatever the verdict may be, the memory of 
Lavoisier shall be saved from any imputation of unfair- 
ness. He was the most generous of men. His noble 
character stands out clearly and luminously in all his 
actions. He was incapable of any meanness. 
We cannot for one moment compare the work of 
Priestley with that of Lavoisier. The elegant methods 
and admirable diction of the latter contrast strangely with 
the clumsy manipulation and prosy phlogistianism of the 
former. “From an ounce of red lead,’’ writes Priestley, 
“heated in a gun-barrel, I got about an ounce measure 
of air, which altogether was worse than common air, an 
effect which I attribute in great measure to phlogiston 
discharged from the iron. The production of air in this 
case was very slow.” Then he heated. without method 
or reason, as Hales had done before him, “flowers of 
zinc, chalk, quicklime, slacked lime, tobacco-pipe clay, 
flint, and muscovy talck, with other similar substances, 
which will be found to comprise almost all the kinds of 
earth that are essentially distinct from each other, 
according to their chemical properties,’ in the hope of 
getting some phlogisticated air from them. What a 
farrago! John Mayow, a century earlier, wrote more 
scientifically ; ‘‘ Si ad flammz naturam serio attendamus, 
et nobiscum cogitemus, qualem demum mutationem 
particule igneze subeunt, dum eadem accenduntur: 
nihil aliud certe concipere possumus, quam _particu- 
larum ignearum accensionem in motu earum perni- 
cissimo consistere. Quidni ergo arbitremur, particulas 
salinas ad ignem constandum pracipue idoneas esse? 
Quze cum maxime solide, subtiles, agilesque sint, motui 
velocissimo, igneoque obeundo multo aptiores esse 
videntur, quam particule sulphurez, crassiores mollissi- 
meeque.”’ 
Priestley’s observations read like the writings of the 
seventeenth century, Lavoisier’s like those of the nine- 
teenth. Compare with the extract given above about the 
“phlogiston discharged from the iron” the following, “I 
have,” writes Lavoisier, “a salt of unknown composition: I 
put a known weight ina retort, add vitriolic acid and distil. 
I obtain acid of nitre in the receiver, and find vitriolated 
tartar in the retort, and I conclude that the substance 
was nitre. I am obliged in this reasoning to suppose 
that the weight of the bodies employed was the same 
after the operation as before, and that the operation has 
only effected a change.” ‘‘J’ai donc fait mentalement une 
équation dans laquelle les matiéres existantes avant 
Vopération formaient le premier membre, et celles obtenues 
apres l’opération formarent le second, et c’est réellement 
par la résolution de cette équation que je suis parvenu au 
résultat. Ainsi, dans l’exemple cité, l’acide du sel que je 
me proposais d’examiner était une inconnue, et je pouvais 
appeler x Sa base m’était egalement inconnue, et je 
pourvais l’appeler y; et puisque la quantité de matiére a 
du étre la méme avant et aprés l’opération, j'ai pu dire 
x+y - acide vitriolique = acide nitreux + tartre vitriolé 
= acide nitreux + acide vitriolique + alcali fixe ; d’ou je 
conclus que + = acide nitreux, y = acide fixe, et que le 
sel en question est du nitre.”’ 
There is nothing in Priestley’s scientific writings which 
exhibits so masterly a treatment as this. Priestley 
ignored Lavoisier’s brilliant conclusions. He died de- 
fending the theory of Phlogiston. He denied the de- 
composition of water. He worked without method or 
order ; and without the balance; and reasoned upon 
facts which lacked verification by quantitative means. 
——— 
