"Better than that," observed Barbican; "we should have been burned
alive."

"Burned alive!" laughed Ardan. "What a pity we missed so interesting an
experiment! How I should have liked to find out how it felt!"

"You would not have much time to record your observations, friend
Michael, I assure you," observed Barbican. "The case is plain enough.
Heat and motion are convertible terms. What do we mean by heating water?
Simply giving increased, in fact, violent motion to its molecules."

"Well!" exclaimed the Frenchman, "that's an ingenious theory any how!"

"Not only ingenious but correct, my dear friend, for it completely
explains all the phenomena of caloric. Heat is nothing but molecular
movement, the violent oscillation of the particles of a body. When you
apply the brakes to the train, the train stops. But what has become of
its motion? It turns into heat and makes the brakes hot. Why do people
grease the axles? To hinder them from getting too hot, which they
assuredly would become if friction was allowed to obstruct the motion.
You understand, don't you?"

"Don't I though?" replied Ardan, apparently in earnest. "Let me show you
how thoroughly. When I have been running hard and long, I feel myself
perspiring like a bull and hot as a furnace. Why am I then forced to
stop? Simply because my motion has been transformed into heat! Of
course, I understand all about it!"

Barbican smiled a moment at this comical illustration of his theory and