th at least as much heat as he expends in a hundred years!"

"A hundred years! Good! Nothing like accuracy!" cried Ardan. "Such
infallible calculators as Messrs. Tyndall and Thomson I can easily
excuse for any airs they may give themselves. They must be of an order
much higher than that of ordinary mortals like us!"

"I would not answer myself for the accuracy of such intricate problems,"
quietly observed Barbican; "but there is no doubt whatever regarding one
fact: motion suddenly interrupted always develops heat. And this has
given rise to another theory regarding the maintenance of the Sun's
temperature at a constant point. An incessant rain of bolides falling on
his surface compensates sufficiently for the heat that he is
continually giving forth. It has been calculated--"

"Good Lord deliver us!" cried Ardan, putting his hands to his ears:
"here comes Tyndall and Thomson again!"

--"It has been calculated," continued Barbican, not heeding the
interruption, "that the shock of every bolide drawn to the Sun's surface
by gravity, must produce there an amount of heat equal to that of the
combustion of four thousand blocks of coal, each the same size as the
falling bolide."

"I'll wager another cent that our bold savants calculated the heat of
the Sun himself," cried Ardan, with an incredulous laugh.

"That is precisely what they have done," answered Barbican referring to
his memorandum book; "the heat emitted by the Sun," he continued, "is
exactly that which would be produced by the combustion of a layer of
coal enveloping the Sun's surface, like an atmosphere, 17 miles in
thickness."

"Well done! and such heat would be capable of--?"

"Of melting in an hour a stratum of ice 2400 feet thick, or, according
to another calculation, of raising a globe of ice-cold water, 3 times
the size of our Earth, to the boiling point in an hour."

"Why not calculate the exact fraction of a second it would take to cook
a couple of eggs?" laughed Ardan. "I should as soon believe in one
calculation as in the other.--But--by the by--why does not such extreme
heat cook us all up like so many beefsteaks?"

"For two very good and sufficient reasons," answered Barbican. "In the
first place, the terrestrial atmosphere absorbs the 4/10 of the solar
heat. In the second, the quantity of solar heat intercepted by the Earth
is only about the two billionth part of all that is radiated."

"How fortunate to have such a handy thing as an atmo