| 
| 
i 
SLSR TASES OG TT SRE BE en eee ee EASE I eo 
290 
ATOM. 
sphere, and all arable land whatever ought, as 
fully as possible, to possess and maintain a porous 
condition. — All the carbonaceous, nitrogenous, 
hydrogenous, and oxygenous portions of manure, 
constituting all but a fraction of both its bulk 
and its value, pass by natural chemical transmu- 
tation into liquid or gaseous forms, and, if not 
economically used before this transmutation 
commences, are dissipated in the atmosphere and 
lost. All strictly organic manure, in fact, begins 
slowly to pass directly or indirectly into an aeri- 
form state the instant its vitality ceases; and it 
proceeds with increasing rapidity in this process 
of decomposition till the whole of it becomes in- 
visible. Carbonic acid is disengaged, and rises 
viewlessly into the atmosphere; nitrogen rushes 
into combination with hydrogen, and sends up 
invisible volumes of ammoniacal gas ; water is 
formed by combination of oxygen and hydrogen, 
and sinks into the ground or runs off with falling 
rain,—in either case, to be eventually carried to 
the clouds in vapour; and just inthe degree in 
which these chemical changes are permitted to 
occur, or in the proportion of time during which 
they are allowed to carry on, the manurial mass 
diminishes in bulk, and is robbed of its fertilizing 
powers. When manure undergoes decomposition 
in the dungyard, on the surface of the field, or 
otherwise in direct exposure to the atmosphere, 
it is wholly lost to the farmer; and only when it 
undergoes decomposition in a state of mixation 
with the soil, does it yield its elements as the 
food of plants. 
ATOM. Theterm atom expresses theoretically 
the smallest particle of matter which is believed 
to be incapable of division into parts. A discus- 
sion has been carried on from ancient times re- 
lative to the finite or infinite divisibility of matter, 
and although the development of the atomic 
theory was supposed to give the strongest evi- 
dence of its limited divisibility, yet it may be 
fairly doubted whether the question can be de- 
cided. The diyisibility of matter apparent to the 
naked eye, and ascertained by calculation, is al- 
most beyond conception. Thus 0:01 of a cubic 
line of silver, dissolved in nitric acid, will pro- 
duce a distinct milkiness in 500 cubic inches of 
clear water containing a trace of common salt, so 
that a particle of silver must be much less than 
the billionth of a eubic line in size. It will give 
a more tangible idea of a billion to say that a 
man counting seconds by a watch day and night 
would require 31,675 years. [Aane.] The appar- 
ent infinite divisibility of matter is more clearly 
shown in the minuteness of living organized 
beings, millions of which would be required to 
constitute a point visible to the naked eye; and 
yet they possess more or less complex systems, 
each part of which again is a porticn of an or- 
ganized structure, which may even consist of 
other complex parts. The mind is lost in at- 
tempting to conceive of a limit in divisibility as 
long as materiality enters into the idea, Again 
ATOMIC THEORY. 
we may divide a line into two parts, one of these 
divisions into two others, and we can conceive it 
to be infinitely divisible, for there must always 
be a part remaining capable of division. On the 
other hand, experiments of Wollaston, Faraday, 
&c., have been adduced in support of the limited 
divisibility of matter. It is found that our atmo- 
sphere has a limit of 45 miles above the earth’s 
surface, from which Wollaston argued that if in- 
finitely divisible, it should’ extend through space 
by infinite repulsive force and be condensed 
around the larger planets, such as Jupiter and 
the sun, forming large and dense atmospheres, 
recognisable by the astronomer. Such atmo- 
spheres not existing, he held that the repulsive 
force is limited, and that the number of repelling 
particles must be finite. Faraday found the 
vapour of bodies formed atmospheres around 
them of definite dimensions, and hence arrived 
at a similar conclusion. It is, perhaps, more ad- 
visable to adopt neither hypothesis, but to rest 
upon experience, for by adopting the view that 
matter has a limit of divisibility, we adopt a 
purely theoretic idea, but, at the same time, we 
cannot ayoid making use of the term particle of 
matter, which implies limited divisibility. If, 
however, we employ the term atom as signifying 
a mass or collection of particles, we pass over the 
question entirely ; and in this sense, atom, atomic | 
weight express a mass of matter and its weight. 
To avoid all collision with the question, we em- | 
ploy the terms equivalent, combining weights, and 
the term atom as an abbreviated expression of | 
the same. 
ATOMIC THEORY. The views respecting 
the combination of elements in different propor- 
tions, were at first more or less hypothetical, and | 
were the foundation of the atomic theory, which 
is based upon the idea of the existence of those | 
ultimate and indivisible particles noticed in the | 
preceding article, These views were successively 
developed by Bergman, Wenzel, Higgins, Richter, 
Mitscherlich, and Dalton ; from the last of whom 
they received a substantial and definite form, ap- 
plicable at least to the resolution of phenomena, | 
as laws of combination, Mr, Dalton’s views are 
unquestionably interwoven with a series of hy- 
potheses, yet these being separated, and the term 
atom being understood, as explained in the last 
part of the preceding article, the so-called atomic 
theory becomes the expression of the fact that 
bodies are obedient to certain definite laws of 
combination; thus, for example, the quantities 
of alkaline bases requisite to neutralize equal 
weights of any-one acid, are proportional to | 
the quantities of the same bases requisite to 
neutralize the same weights of every other acid ; 
and upon this law, in fact, are founded an. infi- 
nite number of important theoretical deductions 
and practical conclusions. A second and highly 
curious and important fact is, that where two 
substances, by combining in different proportions, 
form two or more compounds, the second or third 
t 
