ATO 
being combined with the water than of the 
nitrogen. It is difficult, even by long boil- 
ing, to expel from water the whole of the 
oxygen which it holds dissolved ; and, if ex- 
posed again to the atmosphere, it very 
quickly imbibes it. 
Atmospheric air is an important agent in 
many of the operations of nature. Besides 
serving as the vehicle, of the distribution of 
water, it is, by its mobility, the great agent 
by which temperature is in some measure 
equalized, or at least its extremes moderat- 
ed. Animals, as we have seen, are dependent 
on it for life. It is essential to respiration; 
in the more perfect animals its deprivation 
cannot be sustained for a few moments; 
and even in the less perfect, the abstrac- 
tion of it is followed, though not so im- 
mediately, by death. Its agency depends 
chiefly on its oxygen, a quantity of which is 
spent in every inspiration in producing che- 
mical changes in the blood. A part of its 
nitrogen also is consumed, while a portion 
of carbonic acid gas is formed and expired. 
Vegetable life is also in part dependent on 
it ; it conveys water, and perhaps carbonic 
acid gas, and other principles, to the leaves 
of plants, and is thus subservient to their 
nutrition and growth. 
ATOMICAL philosophy denotes the doc- 
trine of atoms, or a method of accounting 
for the origin and formation of all things 
from the supposition of atoms endued with 
gravity and motion. The atomic physio- 
logy, according to the account given of it by 
Dr. Cudworth, supposes that body is nothing 
else but an extended bulk; and resolves, 
therefore, that nothing is to be attributed to 
it but what is included in the nature and 
idea of it, viz. more or less magnitude, with 
divisibility into parts, figure, and position, 
together with motion or rest; but so as that 
no part of body can ever move itself, but 
is always moved by something else. And 
consequently it supposes that there is no 
need of any thing else besides the simple 
elements of magnitude, figure, site, and 
motion, which are all clearly intelligible as 
different modes of extended substance to 
solve the corporeal phenomena by; and, 
therefore, not of any substantial forms dis- 
tinct from the matter, nor of any other 
qualities really existing in the bodies with- 
out, besides the results or aggregates of 
those simple elements, and the disposition 
of the insensible parts of bodies in respect 
of figure, site, and motion, nor of any inten- 
tional species or shews, propagated from 
the objects to our senses ; nor, lastly, of 
ATR 
any other kind of motion or action really 
distinct from local motion, such as genera- 
tion and alteration, they being neither in- 
telligible as modes of extended substance, 
nor any ways necessary. Forasmuch as the 
forms and qualities of bodies may well be 
conceived to be nothing but the result of 
those simple elements of magnitude, figure, 
site, and motion, variously combined to- 
gether in the same manner as syllables and 
words, in great variety, result from the 
different combinations and conjunctions of 
a few letters, or the simple elements of 
Tspeech ; and the corporeal part of sensation, 
particularly that of vision, may be solved 
only by local motion of bodies, that is, 
either by corporeal effluvia streaming con- 
tinually from the surface of the objects, or 
rather, as the later and more refined ato- 
mists conceived, by pressure made from the 
object to the eye, by means of light in the 
medium. So that the sense taking cogni- 
zance of the object by the subtle interposed 
medium, that is tense and stretched, 
(thrusting every way from it upon the optic 
nerves) doth by that as it were by a staff 
touch it. Again, generation and corruption 
may be sufficiently explained by concretion 
and secretion, or local motion, without sub- 
stantial forms and qualities. And, lastly, 
those sensible ideas of light and colom’s, 
heat and cold, sweet and bitter, as they are 
distinct things from the figure, site, and 
motion of the insensible parts of bodies, 
seem plainly to be nothing else but our own 
fancies, passions, and sensations ; however, 
they be vulgarly mistaken for qualities In 
the bodies without us. 
ATR A bills, in ancient medicine, the 
black bile, one of the humours of the an- 
cient physicians ; which the moderns call me- 
lancholy. Dr. Percival suggests that this dis- 
order is occasioned by the stagnation of the 
gall, by which it is rendered too viscid by 
the absorption of its fluid parts. Bile in this 
state discharged into the duodenum occa- 
sions universal disturbance until it be eva- 
cuated. It brings on vomiting, purging, &c. 
previous to which are fever, delirium, &c. 
ATR ACT Y LIS , in botany, a genus of 
the Syngenesia Polygons ia. class of plants, 
with radiated flowers and compressed seeds,’ 
coronated with a plumose down, and stand- 
ing oh a plane villose receptacle. There 
are eight species, of which' we may notice 
the A. gummifera, gummy-rooted attrac- 
tylis ; root perennial, sending out many nar- 
row leaves which are deeply sinuated, and 
armed with spines on the edges ; these lie 
