withdrawn, the stone falls to the earth. The force which causes this
is called the _attraction of gravitation_, or simply _gravitation_.


How is the second kind of attraction, or that between the particles of
bodies, subdivided?

Into the _attraction of aggregation_, or _cohesion_; and _chemical
attraction_, or _affinity_. The former takes place between particles
which are _similar_, and the latter between those which are
_dissimilar_. All the operations of chemistry are founded upon the
force of affinity which Nature has established between the particles
of different kinds of matter, and which enables the chemist to produce
_new_ compounds differing more or less from the substances by whose
union they were formed.


Is it, then, necessary for chemists to understand the relative nature
of all substances?

Yes; because the basis of this science consists in an _analytical_
examination of the works of Nature; an investigation of the properties
and uses of all substances we are acquainted with; and the study of
the effects of _heat_ and _mixture_, in order that we may find out
their general and subordinate laws.

_Analytical_, relating to analysis.

_Investigation_, act of searching, or tracing out.