d before. Water, in swelling into steam and shrinking
back into water again, moves, of course, twice, and mighty motions these
are, and mighty uses are made of them, I should rather think."

"I believe you, my boy," said Mr. Bagges.

"And now," asked Harry, "have you any idea of what a deal of heat there
is in steam?"

"It is hot enough to scald you," answered his mamma; "I know that."

"Yes; and hot enough, too, to cook potatoes. But there is much more heat
in it than that comes to. Take a kettle of cold water. See at what
degree the thermometer stands in the water. Put the kettle on the fire,
and observe how long it takes to boil. It will boil at two hundred and
twelve degrees; and therefore, during the time it has taken to boil,
there has gone into it the difference of heat between two hundred and
twelve degrees and the degree it stood at when first put on the fire.
Keep up the same strength of fire, so that the heat may continue to go
into the water at the same rate. Let the water boil quite away, and note
how long it is in doing so. You can then calculate how much heat has
gone into the water while the water has been boiling away. You will find
that quantity of heat great enough to have made the water red-hot, if
all the water, and all the heat, had remained in the kettle. But the
water in your kettle will have continued at two hundred and twelve
degrees to the last drop, and all the steam that it has turned into will
not have been hotter--according to the thermometer--than two hundred and
twelve degrees; whereas a red heat is one thousand degrees. The
difference between two hundred and twelve degrees and one thousand
degrees, is seven hundred and eighty-eight degrees; and what has become
of all this heat? Why, it is entirely contained in the steam, though it
does not make the steam hotter. It lies hid in the steam, and therefore
it is called latent heat. When the steam is condensed, all that latent
heat comes out of it, and can be felt, and the quantity of it can be
measured by a thermometer. The warmth that issues from steam-pipes used
to warm a house, is the latent heat of the steam that escapes as the
steam turns back to water."

"Latent, heat! latent heat!" repeated Mr Bagges, scratching his head.
"Eh? Now, that latent heat always puzzles me. Latent, lying hid. But how
can you hide heat? When the zany in the pantomime hides the red-hot
poker in his pocket, he cauterizes his person. How--eh?--how can heat b