Ray 
May 13, 1873) 
substances it is disengaged from them.” In order to determine 
the quantity of air disengaged from any substance during distil- 
lation or fusion, Hales placed the substance ina retort, and luted 
the retort to a large receiver with a small hole, at the bottom ; 
water was caused to occupy a known space in the receiver, and 
the amount of air expelled was estimated by noting the amount 
of water remaining in the receiver at the conclusion of the 
experiment, after cooling. Hales employed the following ap- 
aratus (Fig. 21) to measure the volume of air generated by any 
kind of fermentation, also by the reaction of one body upon 
another. 
The substances undergoing fermentation were placed in 4, and 
over the whole a vessel, @ y, was inverted, closed below by the 
vessel x x, and containing above a certain amount of air, to the 
level y. If air were generated, the water in a sank (say to y) ; 
while if air were absorbed by the bodies in 4, the water rose 
(say to z). Sometimes he placed different substances on pede- 
stais in a jar of air, and ignited them, as Mayow had done, by a 
burning-glass, and noted the alteration in the bulk of air. He 
did this with phosphorus, brown paper dipped in nitre, sulphur, 
and other substances, If he required to act upon substances by 
means of a strong acid, he would place the substance in a 
Fic. 23.—Hales’ pneumatic experiments, 
suitable vessel on a pedestal in a known, v.lume of air, standing 
over water, and would suspend over it a phial which could be 
emptied by pulling a string. ‘Lhese devices were closely copied 
by Priestley and Lavoisier in their experiments upon gaseous 
bodies. If a substance required to be heated violently, it was 
placed in a bent gun-barrel, x x (Fig. 23), one end of which was 
placed in a furnace, while the other was placed under a bell jar, 
a b, full of water, inserted in the pail of water x x. He dis- 
tilled a number of substances, apparently taken at random, and 
determined the amount of gas evolved, but he appears to have 
been at no pains to determine the nature of the gas, assuming it 
to be ordinary atmospheric air. Thus he distilled 1 cubic 
inch of lard, and collected thirty-three cubic inches of gas as the 
products of decomposition. Tallow, horn, sal ammoniac, 
oyster shells, peas, amber, camphire, and many other substances, 
were similarly treated. 
Two grains of phosphorus ignited in a closed vessel of air, 
were found to absorb 28 cubic inches of air. 211 grains of 
nitre mixed with bone-ash yielded 90 cubic inches of gas; 54 
cubic inches of water on boiling yielded 1 cubic inch of air. In 
order to measure the elastic force of the gas produced by fer- 
menting peas, Hales filled a small, strong bottle, ¢ (Fig. 22) with 
peas, filling up the interstices with water ; mercury to a depth 
NATURE 
57 
of half an inch was then poured in, and of course remained at 
the bottom of the vessel c. A long tube, a z, the lower end 
of which dipped beneath the mercury, was securely fastened 
into the mouth of the bottle 4, and fixed air-tight. In a few 
days’ time the peas were in a state of fermentation, and the 
generated gas had forced the mercury to ascend in the tube @ z 
to a height of 80 inches, hence the gas in ¢ was existing under a 
pressure of about 35 Ibs. on the square inch. 
Hales also produced gases by various reactions. Thus he 
poured a cubic inch of sulphuric acid on half a cubic inch ot 
iron filings: no effect took place until he had diluted the acid 
with water, when forty-three cubic inches of azr (as he calls it— 
in reality hydrogen gas) came off. Iron filings mixed with nitric 
acid, or with ammonia, or sulphur, were found to absorb air. A 
cubic inch of chalk treated with dilute sulphuric acid produced 
thirty-one cubic inches of az (in reality carbonic anhydride gas). 
If space permitted, we could say much more of Hales’ works. 
His experiments on respiration, and on various principles of 
vegetation, are exceedingly ingenious, and often accurate. It 
has often been said that Lavoisier created modern chemistry by 
the introduction of the balance into chemical experiments, but 
here we find Hales weighing his substances, and measuring his 
gases, years before Lavoisier was born. Hales did not suffh- 
ciently investigate the nature of the various gases which he pro- 
duced in the course of his experiments, but he assuredly paved 
the way for many of the after discoveries of Priestley, Cavendish, 
and Lavoisier. 
Dr. Hermann Boerhaave, of Leyden (b. 1668, d. 1738), was 
a contemporary of Hales. He was the author of the first com- 
prehensive system of chemistry :—a bulky quarto in two volumes, 
entitled Z/ementa Chemie, which appeared in 1732, and which 
for many years was the chemical text-book of Europe. In it he 
defines chemistry as ‘‘an art which teaches the manner of per- 
forming certain physical operations, whereby bodies cognizable 
to the senses, or capable of being rendered cognizable, and of 
being contained in vessels, are so changed by means of proper 
instruments, as to produce certain determinate effects, and at 
the same time discover the causes thereof for the service of 
various arts.” 
But hold! our task was to give some account of the é27th of 
chemistry, while a science with such a ponderous definition as 
the above, is no longer infantile. The babe has grown up about 
us until it has assumed a tremendous individuality. The great © 
discoveries of the fathers of modern chemistry, Lavoisier, 
Scheele, Priestley, Cavendish, Davy, need not be told here; they 
belong to the later history of chemistry. We have traced the 
science from its commencement in the crude metallurgical and 
other operations of the ancients, to the time when a comprehen- 
sive system of the science appeared. And when we think of 
the vast dimensions of the science of to-day, the numberless text- 
books in every language, the great laboratories springing up in 
every country, the immense amount of original research, we are 
carried back in spirit to those mistaken—but often grandly 
energetic men—who said to the disciples of their art :— 
Ora! 
Lege, Lege, Lege, Relege, Labora! 
Et Invenies. 
G. F. RoDWELL 
SCIENTIFIC SERIALS 
Bulletin Mensuel de la Socitté d@ Acclimatation de Paris. 
The April number contains much interesting information as 
to the work done by the Society, which besides gratuitously dis- 
tributing specimens of various useful animals or plants wherever 
they are likely to thrive, also lends or lets to those persons, whose 
tastes or knowledge fit them for the charge, some of the rarer 
species of animal or vegetable life, thus sowing the seeds 
of miniature jardins d’acclimatation throughout the country. 
During the last 12 months 3 monkeys have been born at 
the Paris Gardens, one of them in March last. In that month 
75 mammalia and 1,669 birds of various sorts were received, 
while the Society was able to distribute 62 mammalia and 1,731 
birds. The Society aims at encouraging the reproduction of all 
sorts of useful animals, not merely confining its efforts to the 
maintenance of a stock for exhibition. An interesting account 
is given of an oyster breeding establishment and aquarium at 
Biarritz, and of the cultivation of silkworms in France generally, 
Our French neighbours have set us the example of cultivating 
