s concerned. No doubt there are certain other planets besides the
earth, and they will receive quantities of heat to the extent of a few
cents more. It must, however, be said that the stupendous volume of
solar radiation passes off substantially untaxed into space, and what
may actually there become of it science is unable to tell.

And now for the great question as to how the supply of heat is
sustained so as to permit the orb of day to continue in its career of
such unparalleled prodigality. Every child knows that the fire on the
domestic hearth will go out unless the necessary supplies of wood or
coal can be duly provided. The workman knows that the devouring blast
furnace requires to be incessantly stoked with fresh fuel. How, then,
comes it that a furnace so much more stupendous than any terrestrial
furnace can continue to pour forth in perennial abundance its amazing
stores of heat without being nourished by continual supplies of some
kind? Professor Langley, who has done so much to extend our knowledge
of the great orb of heaven, has suggested a method of illustrating the
quantity of fuel which would be required, if indeed it were by
successive additions of fuel that the sun's heat had to be sustained.
Suppose that all the coal seams which underlie America were made to
yield up their stores. Suppose that all the coal fields of England and
Scotland, Australia, China, and elsewhere were compelled to contribute
every combustible particle they contained. Suppose, in fact, that we
extracted from this earth every ton of coal it possesses, in every
island and in every continent. Suppose that this vast store of fuel,
which is adequate to supply the wants of this earth for centuries,
were to be accumulated in one stupendous pile. Suppose that an army of
stokers, arrayed in numbers which we need not now pause to calculate,
were employed to throw this coal into the great solar furnace. How
long, think you, would so gigantic a mass of fuel maintain the sun's
expenditure at its present rate? I am but uttering a deliberate
scientific fact when I say that a conflagration which destroyed every
particle of coal contained in this earth would not generate so much
heat as the sun lavishes abroad to ungrateful space in the tenth part
of every single second. During the few minutes that the reader has
been occupied over these lines, a quantity of heat which is many
thousands of times as great as, the heat which could be produced by
the