a 
| and antennaria. 
| Greek synonyme of everlasting, and literally 
ASTROLOBIUM. 
- ASTROLOBIUM. A genus of ornamental 
hardy annual plants, of the pea tribe. The spe- 
cies in Britain are four; they are natives of 
Barbary and the south of Hurope; they were 
formerly included in the ornithopus or bird’s-foot 
genus; and they grow about six inches high, 
have star-like pods, and produce yellow flowers 
in June and July. 
ATHALIA. See Turnie-F xy. 
ATHAMANTA. A genus of herbaceous plants, 
of the umbelliferous family. One species is popu- 
larly called the Cretan carrot, another the Sicilian 
carrot, and another wild rosemary ; but most are 
| known under the name of SprcknEL: which see. 
- ATHANASIA. A genus of ornamental, ten- 
der, evergreen, shrubby plants, of the composite 
family. They are of the kind popularly called 
everlastings, from the durable nature of their 
flowers; but they suffer some depreciation by 
sharing that name with the genera gnaphalium 
The name athanasia is a mere 
means deathless. Upwards of fifteen species of 
athanasia have been introduced from the Cape of 
Good Hope; and ten or twelve more are known 
to botanists. The name athanasia was formerly 
given to tansy, “ either,” says Dr. Turton, “ be- 
cause its flowers do not easily wither, or because, 
‘if it is stuffed up the nose of a dead corpse, it 
prevents putrefaction.” 
ATHEROPO’GON. A genus of grasses, of the 
| tribe subbifloree. The name signifies ‘a bearded 
awn; and alludes to one prominent character of 
the genus. Though upwards of fifteen species 
are known to botanists, only one, Atheropogon 
| apludoides, exists in Great Britain; and this was 
introduced, about 80 years ago, from the south 
| of Europe. It isa hardy, half-beautiful perennial, 
grows 9 inches high, and produces its apetalous 
flowers in August. Some botanists call it Chloris 
curtipendula,; and others, Dinebra curtipendula. 
ATMOSPHERE. The immense mass of elastic 
fluid which surrounds the globe which we inhabit 
is called its atmosphere, and the mixture of gases 
| of which it consists, atmospheric air, or simply 
the air. Nothing perhaps can be more interest- 
ing than a knowledge of the nature of this fluid 
in which we live and move: so intimately con- 
| nected, indeed, is our whole existence and that 
| of all other living beings with the atmosphere, 
that those planetary bodies in which no atmo- 
| sphere has been discovered are generally consi- 
| dered in consequence thereof destitute of organic 
beings. As our life depends for its existence and 
continuance on it, so our health and comfort are 
intimately connected with the changes which it 
undergoes, and cannot therefore be attended to 
| without knowledge of its physical and chemical 
nature. If it be furthermore remembered that 
the atmosphere is the principal agent in com- 
bustion, and that, until the discovery of the 
steam-engine, it constituted an important me- 
chanical power on which, until lately, navigation 
ATMOSPHERE. 281 
has from time immemorial been dependent, and 
that possibly the time is not far distant when it 
may become the principal medium for locomo- 
tion, its importance in the condition and devel- 
opment of mankind will easily be conceived. 
Chemical nature of the atmosphere. — Common 
atmospheric air was for a long time considered 
as a simple element. The first knowledge of the 
composition of the atmosphere must have been 
after the period of the discovery of oxygen gas 
by Dr. Priestley in 1774. Lavoisier, indeed, in 
his posthumous works, appears to insinuate a | 
knowledge of it in 1772. But this claim cannot 
be admitted, as he gives no hint of any such 
knowledge in his volume of essays published after 
that period, and as he was entirely unacquainted 
with oxygen gas when Priestley showed him the 
way to prepare it at Paris, about the end of 1774. | 
It is very probable that Lavoisier became ac- 
quainted with the composition of atmospherical 
air not very long after that period ; though some 
years elapsed before he made it known to the 
public. Whether he preceded Scheele in his 
knowledge of this important fact, we do not 
exactly know. But there is no doubt whatever 
that Scheele’s investigations were carried on | 
without any assistance from abroad, and that it | 
was in consequence of the publication of his 
‘Treatise on Air and Fire,’ that the chemical world 
became acquainted with the nature and compo- | 
sition of atmospherical air. This important work 
was printed at Upsal in 1777, with an introduc- 
tion by Bergmann, and translated into English | 
by Dr. Foster in 1780. The experiments of 
Priestley indeed would have warranted the con- | 
clusions respecting the composition of atmo- | 
spherical air drawn by Scheele; but those of Dr. | 
Priestley were different and more complicated. | 
In Scheele’s first experiments, he estimated the 
bulk of oxygen gas in air at 30 per cent. 
continued for a whole year, in order to ascertain 
whether the bulk of oxygen in air be constant, 
or varies with the season of the year. 
it in general remarkably constant, and. amount- 
ing to 27 per cent. 
and the greatest observed was 30 per cent. 
Priestley had made similar experiments, and had 
estimated the bulk of the oxygen at }th of the 
air, or 20 per cent. Mr, Lavoisier’s experiments, 
which were very numerous and varied, almost 
coincided with those of Scheele. He considered 
air as composed of 27 parts by bulk of oxygen, 
and 73 of azote. Mr. Cavendish’s experiments 
were published in the Philosophical Transactions 
for 1783. He proved decisively that the propor- 
tion of the azote and oxygen in the atmosphere 
does not vary; and by a very careful analysis, con- 
cluded, that 100 parts of air in bulk are composed of 
79:16 azote 
20°84 oxygen 
100-00 
But in | 
the year 1779, he published a set of experiments | 
He found | 
The smallest bulk was 24, | 
Dyin. | 
a 
