A 
_ exist no attraction, at least they cannot be made to combine together. 
BOTANIC PHYSICIAN. 
nce to every other. Between many substances there seems to. 
Others have a very extensive power of combination, and seem capa- 
ble of uniting with almost every substance which is not already 
saturated with them ; and there are many intermediate, in their facili- 
ty of combination, between these two extremes. e 2 
_ Chemical attraction is not limited, in its action, to two bodies. It 
can be exerted between three, four, or more, and can thus form com-- 
pounds of so many principles. It can likewise unite bodies in differ- 
ions. Some combine in every proportion, others only in. 
mDLD 
_ limited quantities. In the latter case, the compounds formed by the. 
different proportions have in general very different properties. _ 
The compounds which are thus formed, have still the same rela- 
tion to chemical attraction. ‘They have a tendency to combine with 
other bodies, simple or compound ; they can combine in various 
numbers and proportion ; and these combinations are accompanied 
the same phenomena, and regulated by the same laws. 
attraction exerted by any substance towards others, is not 
in its force. To some it is stronger, to others weaker. 
ice it follows, that if two bodies have been combined together, 
they may be separated, or the compound they have formed maybe 
destroyed by presenting to it another substance, which exerts an-  _ 
_attraction to one of its component parts, superior to the attraction | 
by which they were held united. If the circumstances neces 
Sary to’ favor the exertion of chemical attraction be present, the 
is the strongest attraction combine, 
Se chemical language this process is — 
termed decomposition, from a single elective attraction. pee 
re complicated, is that, where two. 
‘and where the constituent parts of | 
exertion of a double elective attraction. Tables have been cote 
structed of the relative forces of attractions of many bodies towards 
others, whence may be estimated the combinations or decompositions 
that will take place on their mixture with éach other. } 
The exertion of chemical attraction between bodies is greatly influ- 
enced by another power, that of heat or caloric. This is the cause 
of the temperature of bodies, of their expansion, fluidity, and con- 
Version into the eriform or gaseous state. Its influence or chemical 
combination and decomposition is very extensive. Some: bodies 
combine together at the common temperature of the atmosphere; 
others require that temperature to be raised ; and in some it is ne- 
cessary to expose them toa very intense heat. ‘The same difference 
take place with respect to decomposition. Many bodies remain in 
chemical union within a certain range of temperature, more or less. 
extensive ; but whenever the heat, to which the compounds in which — 
they exist are exposed, is increased beyond a certain degree, decom= 
position takes place, and the constituent principles are separated 
from cach other. These effects are partly to be explained from the. 
