e science itself. Order is required in
reasoning, because all reasoning is employed in deducing propositions
from one another in a regular series; but where terms are employed
merely as names, this order may be dispensed with. It is, however, of
great consequence to seize the proper time for introducing a new term;
a moment when attention is awake, and when accident has produced some
particular interest in the object. In every family, opportunities of
this sort occur without any preparation, and such opportunities are
far preferable to a formal lecture and a splendid apparatus for the
first lessons in natural philosophy and chemistry. If the pump
belonging to the house is out of order, and the pump-maker is set to
work, an excellent opportunity presents itself for variety of
instruction. The centre pin of the handle is taken out, and a long rod
is drawn up by degrees, at the end of which a round piece of wood is
seen partly covered with leather. Your pupil immediately asks the name
of it, and the pump-maker prevents your answer, by informing little
master that it is called a sucker. You show it to the child, he
handles it, feels whether the leather is hard or soft, and at length
discovers that there is a hole through it which is covered with a
little flap or door. This, he learns from the workmen, is called a
clack. The child should now be permitted to plunge _the piston_ (by
which name it should _now_ be called) into a tub of water; in drawing
it backwards and forwards, he will perceive that the clack, which
should now be called the valve, opens and shuts as the piston is drawn
backwards and forwards. It will be better not to inform the child how
this mechanism is employed in the pump. If the names sucker and
piston, clack and valve, are fixed in his memory, it will be
sufficient for his first lesson. At another opportunity, he should be
present when the fixed or lower valve of the pump is drawn up; he will
examine it, and find that it is similar to the valve of the piston; if
he sees it put down into the pump, and sees the piston put into its
place, and set to work, the names that he has learned will be fixed
more deeply in his mind, and he will have some general notion of the
whole apparatus. From time to time these names should be recalled to
his memory on suitable occasions, but he should not be asked to repeat
them by rote. What has been said, is not intended as a lesson for a
child in mechanics, but as a sketch of