runs into this cylindrical receptacle through the lower
plate; it penetrates the latter and then takes the form of
a helicoidal or screw-shaped spiral, the rings of which,
rising one over the other, occupy nearly the whole of the
height of the tank. Before again issuing from it, this
spiral runs into a small cone with a concave base, that is
turned downward in the shape of a spherical cap.

"It is from the top of this cone that the second pipe
issues, and it runs, as I have said, into the upper beds of
the balloon.

"The spherical cap of the small cone is of platinum, so
as not to melt by the action of the cylinder and blow-pipe,
for the latter are placed upon the bottom of the iron tank
in the midst of the helicoidal spiral, and the extremity of
their flame will slightly touch the cap in question.

"You all know, gentlemen, what a calorifere, to heat
apartments, is. You know how it acts. The air of the
apartments is forced to pass through its pipes, and is then
released with a heightened temperature. Well, what I
have just described to you is nothing more nor less than a
calorifere.

"In fact, what is it that takes place? The cylinder
once lighted, the hydrogen in the spiral and in the
concave cone becomes heated, and rapidly ascends through
the pipe that leads to the upper part of the balloon. A
vacuum is created below, and it attracts the gas in the