we consider the immense variety of objects which present
themselves to the eye, it most appears, at first sight,
impossible to acquire even a general knowledge of their
qualities and properties.
The longest life, with the most vigorous mind, and the most
persevering industry, would be wholly unequal to the task of
examining even the individual objects of all kinds with which a
single man is surrounded. Hence it arises that, by a natural law
of the human mind, we are always tempting to arrange the objects
of our inquiries into certain classes, wording to certain common
properties which they seem to possess.
These are divided into other classes, with additional marks of
distinction; and these are again subdivided into other sets,
until we at last come down to the individual object.
By this process the mind is suited in its inquiries, and the
communication of knowledge is rendered easy and useful. The
study of all the objects of our senses may be divided into two
branches, namely, Natural History, and Natural Philosophy.
The first of these branches is occupied in arranging objects,
and describing them in such a way that they may be easily and
accurately distinguished from one another. It may be considered
as a descriptive view of the material world, in a state of rest
or inactivity, without taking into account the motions or
actions of bodies upon one another.
This is the first step in the progress of knowledge, and it
constitutes Natural History.
But the operations of nature are seldom to rest: change succeeds
change; new combinations of objects are formed, and new
productions make their appearance. The primary planets revolve
round the sun as their center; the secondary planets or moons
perform similar revolutions round their primaries.
The air of the atmosphere presses on the surface of the earth,
with a certain force. A stone when unsupported falls to the
ground, in a line pointed towards the centre of the globe. Water
deprived of a certain portion of its heat becomes solid in the
form of ice: but if combined with a greater portion of heat than
what is necessary to keep it fluid, water is converted into
vapour, ascends into the atmosphere, is there again robbed of
its extra heat, and returns to the earth in the form of rain; or
if still more heat be taken away, it appears as snow or hail.
A seed is placed in the ground, and if heat moisture and air be
applied, it shoots and springs up: with the addition of light,
if the operation be continued, it becomes a new plant, puts
forth leaves and flowers, and produces seed similar to that
first placed in the ground.
to determine what are these changes, to observe the laws by
which such changes are effected, and to ascertain the measure
and quantity of the effect produced, all this belongs to that
branch of knowledge which is included under the general term
Natural Philosophy, also called Physics.
But of these changes and motions some are obvious to our senses,
others entirely escape our observation. We see a stone fall to
the earth, and experience tells us that it falls with a force
proportioned to its weight, and the height from which it fell.
The change or motion which takes place, when water puts on a
solid form, when a fluid undergoes the process of fermentation,
or when a combustible body is burnt, all this is totally
imperceptible by our senses.
Thus Natural Philosophy is divided into two branches: the
objects of the first are the sensible changes or motions
observable in the material world, and the consideration of these
objects is, strictly and properly speaking, Natural Philosophy
or Physics: the second branch, which is employed in discovering
the laws and ascertaining the effects of the insensible changes
or motions of bodies, constitutes the science of Chemistry.