The steam engine familiarly explained and illustrated; with an historical sketch of its invention and progressive improvement; its applications to navigation and railways; with plain maxims for railway speculators. By the Rev. Dionysius Lardner ... With additions and notes by James Renwick ...

FIRST STEPS IN THE INVENTION. 41
just, therefore —mere suggestions and abortive experiments
though they may have been-to record them, that each inventor and discoverer may receive the just credit due to his
share in this splendid mechanical invention. We shall then
in the present chapter briefly enumerate, in chronological
order, the successive steps so far as they have come to our
knowledge.
HERO OF ALEXANDRIA, 120 B C.
(23.) In a work entitled Spiritalia seu Pnzeumatica,
one of the numerous works of this philosopher which has
remained to us, is contained a description of a machine
moved by vapour of water. A hollow sphere, of which A B
represents a section, is supported on two pivots at A and B,
which are the extremities of tubes A c D and B E Fr which
pass into a boiler where steam is generated. This steam
flows through small apertures at the extremities A and I,
and fills the hollow sphere. One or more horizontal arms
K G, I H, project from this sphere, and are likewise filled
with steam, but are closed at their extremities. Conceive a
Pig. 1.
small hole made near the extremity G, but at one side of one
of the tubes; the steam confined in the tube and globe would
immediately rush from the hole with a force proportionate
to'ts pressure within the globe. On the common principle
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