"I can see a part of a great laboratory from where I am sitting," returned Johnny, who was sitting on the doorstep. "Or, at least, I can see a part of one of its distilleries."
Pierre began to smile.
"I can't see any of its great retorts," continued Johnny, "nor the furnaces under them, nor the gas burned as it comes out. But I can see a good many of the contrivances for storing up heat so that it can be kept cool in a very useful, beautiful form until the heat is needed, when it can very easily be brought out again in flames. And I can see some more of the stored heat that has gone through a second process, by which it serves the purpose of slow combustion, which gives heat and force without any light."
Pierre began to laugh. "Can't you guess the riddle now?" he said.
But the children still looked puzzled.
"Oh! I haven't been trying to guess," said Felix: "I think riddles are more trouble than they are worth."
"There is a good deal of the slow combustion going on in this veranda," continued Johnny, "and some of the stored-up force; though the machines might be made a good deal more active, if it were not just after dinner-time, when the fuel that's been put in is in a pretty compact form, and hasn't begun to be distributed much. In an hour or two the machines may get quite antic."
"He means us, by the machines, don't he?" said Julia.
"But what do you mean by the great retorts?" asked Felix.
"And the heat stored up in a cool form?" added Ruth.