<b avoid presenting facts for illustration, in 
vrliich more than three principles were con- 
terned ; though the doctrines to be eluci- 
dated supposed no more than that number 
to be present. This supposition can admit 
only of one combination, either of two or of 
three principles; but in the complex effects 
of chemical attraction, four or more bodies 
may be treated of as forming distinct and 
separate combinations ; and these com- 
pounds being presented to each other, may 
be aftccted by all the habitudes and cir- 
cumstances upon which we have so long 
dwelled, besides such others as arise from 
their greater complexity. These cannot 
be here fully treated. It will be sufficient 
at present to overlook tliose effects wherein 
compounds of many principles may be 
formed, or in whicli the intermediate, or 
resulting, or disposing attractions may ope- 
rate, and regal'd only the cases in which 
two binary compounds, being presented to 
each other, do either remain unaltered, or 
efse exchange their principles so as to form 
two other binary compounds. A few years 
ago this was thought to comprehend the 
greatest part of the doctrine of chemical 
attractions; but as practical science ad- 
vances the supposed simplicity ot the facts 
becomes less than before. 
These phenomena, afforded by two binary' 
compounds,, have been cl.issed under the 
denomination of effects of double elective 
attraction. These facts may be considered 
with regard to the whole force of the attrac- 
tions that tend to retain the original com- 
pounds, which have been Called quiescent 
attractions, and the whole force of the 
attractions that tend to produce two new 
binary compounds, which have been called 
divellent attractions. If the former be the 
greatest, the change will not take place ; 
but if the latter exceed, it will. Thus, if to 
the sulphate of potash lime be presented, the 
sulphuric acid being more strongly attracted 
by potash than by lime, no decomposition will 
ensue : but if muriate of lime be presented 
to the sulphate of potash, the lime will not 
only attract the sulphuric acid, but the mu- 
riatic acid will attract the potash ; and the 
sum of the divellent attractions, namely, of 
the lime to the sulphuric acid, of the mu- 
riatic acid to the potash, being greater than 
tlie sum of the original or quiescent attrac- 
tions ; namely, of the sulphuric acid to the 
. potash, and of the muriatic acid to the lime, 
two new- compounds, namely, sulphate of 
lime .and muriate of potash, will be formed. 
See Elective Atxraciiok. 
VOL. II. 
5TRY. 
The most essential difference between 
the complicated cases of attraction here 
described, and those treated of just before, 
is, that tlie principles in these last are either 
saturated, or nearly so, when presented to 
each other ; and Ifom this difference, and 
the number of principles, it is that the 
effect of solvents, the force of cohesion 
and of elasticity, as well as of temperature, 
and other circumslances, act with more 
effect than in the simpler cases. 
Whenever the cohesive attraction ope- 
rates so as to form solid aggregates, whetlier 
by the congelation of fused bodies by cool- 
ing, or the deposition of bodies from their 
solvents, the aggregates, if not disturbed 
by too rapid condensation, or by other 
causes, have the form of solids bounded by 
flat surfaces, meeting each other iu certain 
definite angles. The.se solids are callhd 
crystals. The property of crystallizing 
seems to be a natural consequeoce of the 
resulting attractions. For if a binary com- 
pound be attracted by any other principle 
or compound, and the time and circum- 
stances allow the particles to turn round, it 
appears obvious that the appulse and adhe- 
sion will be made by such sides of the 
bodies as are occupied by particles most 
strongly attractive of each other; and this 
regularity of apposition must produce regu- 
larity of figure. See Cft-vsTALLizATibN. 
After this general statement of the means 
and agents of chemistry, it remains only for 
us in this general ai ticle to give an outline of 
the different substances or principles upon 
which the processes of nature and art are 
performed, and upon which the articles de- 
voted to each may be Consulted. 
CHEMICAL ARRANGEMENT OF BODIES. 
I. Substances imt yet decomposed^ called 
simple principles. 
1 . Principles of doubtful existence. These 
are (a) heat, (6) light, and the causes of 
(c) galvanic, (d) electric, and (e) magnetic 
phenomena. These energies cannot be Con- 
fined in vessels; they are not measurable 
by figured extension or by gravity ; we know 
nothing of their compounds ; and they ac- 
company and are excitable in other bodies by 
manipulation : from which, and other reasons, 
they have been thought to be modes, pro- 
perties, or occasional habitiules of bodies. 
But, on the other hand, they possess so 
many distinctive charactei-s, that a large 
class of philosophers ascribe them to certain 
peculiar fluids, or to one common fluid. Se* 
Ether. 
M 
