ent could invent
it. Mr. E---- thus stated the difficulty: "In the old steam engine,
cold water, you know, is thrown into the cylinder to condense the
steam; but in condensing the steam, the cold water at the same time
cools the cylinder. Now the cylinder must be heated again, before it
can be filled with steam; for till it is heated, it will condense the
steam. There is, consequently, a great waste of heat and fuel in the
great cylinder. How can you condense the steam without cooling the
cylinder?"

S----. "Let down a cold tin tube into the cylinder when you want to
condense the steam, and draw it up again as soon as the steam is
condensed; or, if you could put a _cylinder_ of ice up the great
tube."

Some of the company next asked, if an horizontal plate of cold metal,
made to slide up the inside of the cylinder, would condense the steam.
The edges of the plate only would touch the cylinder; the surface of
the plate might condense the steam.

"But," said Mr. ----"how can you introduce and withdraw it?"

C---- (a girl of 12) then said, "I would put a cold vessel to condense
the steam at the top of the cylinder."

Mr. ----. "So as to touch the cylinder, do you mean?"

C----. "No, not so as to touch the cylinder, but at some distance from
it."

Mr. ----. "Then the cold air would rush into the cylinder whilst the
steam was passing from the cylinder to your condenser."

C----. "But I would cover in the cold vessel, and I would cover in the
passage to it."

Mr. ----. "I have the pleasure of informing you, that you have
invented part of the great Mr. Watt's improvement on the steam engine.
You see how it facilitates invention, to begin by stating the
difficulty clearly to the mind. This is what every practical inventor
does when he invents in mechanics."

L---- (smiling.) "And what _I_ always do in inventing a mathematical
demonstration."

To the good natured reader we need offer no apology; to the ill
natured we dare attempt none, for introducing these detailed views of
the first attempts of young invention. They are not exhibited as
models, either to do honour to the tutor or his pupils; but simply to
show, how the mind may be led from the easiest steps, to what are
supposed to be difficult in education. By imagining ourselves to be in
the same situation with children, we may guess what things are
difficult to them; and if we can recollect the course of our own minds
in acquiring knowledge, or in inventing,