Z 24,1873) 
Tt was well known that if a piece of red-hot charcoal be 
thrown into melted nitre, it is consumed with great rapidity, 
while in the air it burns wih far less readiness ; hence Hooke 
infers that that particular component of air which causes it to 
_ support combustion exists in a condensed form in saltpetre. He 
also remarks that if air be violently forced upon a piece of ignited 
_ charcoal by bellows it may be made to burn almost as rapidly as 
in melted nitre. 
12, ‘It seems reasonable to think that there is no such thing 
_asan element of fire... . but that that shining transient body 
- called fame is nothing else but a mixture of air and volatile sul- 
phureous parts of dissoluble or combustible bodies.” 
_ Hooke asserts that this theory had been worked out by him 
several years earlier, and had been well supported by experi- 
mental means; he says, moreover, that he has here “only time 
to hint an hypothesis, which, if God permit me life and oppor- 
tunity, I may elsewhere prosecute, improve and publish.” This 
he never did ; but a young Oxford physician named John Mayow 
(b. 1645 d. 1679) eagerly accepted the theory, and adduced 
many experiments in support of it. Perhaps Mayow may have 
worked with Hooke, during his residence in Oxford, and may 
have helped to adduce verifications of the then half-formed 
theory. Mayow’s experiments are contained in a treatise en- 
tiled—** Zractatus Quinqgue Medico-Physici quorum primus 
a 
' 
ty 
* 
Fic, 18.—John Mayow. 
(From his “Tractatus Quinque Medico-Physici, 1674.”) 
agit de Sal-nitro et Spiritu Nitro-aéreo, Secundus de Respira- 
tione... . Oxonii, 1674.” The book is altogether important, 
because the experiments which it contains form the basis of pneu- 
matic chemistry, that is the chemistry of gaseous bodies ; it is 
also distinguished by accurate reasoning and well-founded 
eneralisations. ad it been better known, it can scarcely be 
oubted that the discovery of oxygen and of various gases made 
a century ago, would have been forestalled by many years. 
Mayow calls the ‘‘dissolving parts” of the air and of nitre, 
_ which we now call oxygen gas, by the several names of zitre-air, 
fire-air, and nitvo-aévial sfirit, Air does not consist wholly of 
nitre-air, because when a candle is burnt in a closed vessel only 
a portion of the contained air is consumed. Nitre-air exists in 
large quantities in a condensed form in nitre ; hence combustible 
bodies mixed with nitre will burn under water, or in a vacuum. 
‘The acid of nitre contains all the nitre-air in nitre, but it does 
not inflame bodies so readily as nitre because in it the nitre-air 
is surrounded by particles of water which tend to quench the 
‘burning body. Nitre-air is not combustible itself, neither does 
nitre contain any combustible substance, because it may be 
sed in a red-hot crucible, but no ignition will be observed to 
ROE e Ie Se 
Sri 4 ‘ 
NATURE 
493 
take place, until a combustible body has been added. All acids 
contain nitre-air :—how curi susly this conrasts with Lavoisier’s 
name oxygen, from ofus yevvaw, which he gave to the gas, be- 
cause he believed it to be an essential constituent of all acids, 
Sulphuric acid, according to Mayow, consists of nitre-air united 
with es des ; Wines become sour and are changed into vinegar 
by the absorption of nitre-air from the atmosphere. It is the 
cause also of fermentation and putrefaction, and for this reason, 
substances when covered with fat or oil do not putrefy, During 
calcination metals increase in weight, and this increase is attri- 
buted by Mayow to absorption of nitric air; thus calx of antimony 
is antimony f/us nitre-air, and this is borne out by the fact that 
a substance absolutely similar to calx of antimony may be pros 
cured by treating the metal with the acid of nitre and evapoe 
rating. Again, rust of 1ron is iron united with nitre-air. 
We come now to some of the first experiments in Pneumatic 
Chemistry, In one of his experiments Mayow supported a kind 
of ledge within a bell-jar full of air (see Fig. 19) ; upon the ledge 
he placed a piece of camphor, and fired it by concentrating the 
rays of the sun bya lens upon it. The camphor ignited and 
burnt for some time, water then rose in the jar; and on again 
attempting to ignite the camphor he was unsuccessful. A lighted 
candle was also burned in the jar with the same result. Thus a 
part only of the air had been consumed, and the remainder was 
unable to support combustion. The siphon tube (shown on the 
right-hand side of the figure) was inserted at the commencement 
in order to render the height of the water the same, inside and 
outside the tube, as stoppered air jars were then unknown. 
Thus it was clearly proved that air is diminished in bulk by 
combustion, In order to prove that respitation produces a 
Fic. 20. 
Fig. 20.—Early ex- 
Fic. 19. 
Fig. 19.—Early experiment in pneumatic chemistry. 
periment in physiological chemistry. 
similar result, Mayow tied a piece of moist bladder over the 
mouth of a jar (Fig 20), and upon this he pressed a cupping- 
glass, so that the edges fitted air-tight Within the cupping- 
glass he placed a mouse, and as the animal continued to breathe 
he noticed that the bladder was forced up, more and more into 
the cupping-glass, proving that the air within it had been dimi- 
nished by the respiration. Thus Mayow endeavoured to esta- 
blish a connection between combustion and respiration. He 
also placed a mouse in a vessel standing over water, and noticed 
that the water rose in the jar as the respiration continued ; and 
he found it impossible to ignite a combustible body in a jar of 
air in which a mouse had died. Again, he placed a mouse and 
a lighted candle together in a jar of air, and he noticed that the 
mouse only lived half as Jong as a mouse lived in the same bulk 
of air without the candle. Air deprived of its nitre-air was 
assumed to be lighter than nitre-air, because if a mouse is placed 
near the top of aclosed vessel, it dies sooner than if placed near 
the bottom. : 
In 1672 Robert Boyle procured hydrogen gas by acting upon 
iron filings with an acid, and proved its nflammability ; but he 
does not appear to have further studied its properties, and its 
discovery is always attributed to Cavendish, a century later. 
Boyle suggests that it probably consists of *‘ the volatile, sulphur 
of Mars, or of metalline steams participating in a sulphurous 
nature.” Mayow also procured some of this gas by acting upon 
