such simple means as should give
the required precision in the percussive action of the falling mass.
Following out this idea, Mr. Nasmyth at once sketched on paper his
steam-hammer, having it clearly before him in his mind's eye a few
minutes after receiving Mr. Humphries' letter narrating his
unlooked-for difficulty. The hammer, as thus sketched, consisted of,
first an anvil on which to rest the work; second, a block of iron
constituting the hammer or blow-giving part; third, an inverted
steam-cylinder to whose piston-rod the block was attached. All that
was then required to produce by such means a most effective hammer, was
simply to admit steam in the cylinder so as to act on the under side of
the piston, and so raise the block attached to the piston-rod, and by a
simple contrivance to let the steam escape and so permit the block
rapidly to descend by its own gravity upon the work then on the anvil.
Such, in a few words, is the rationale of the steam-hammer.

By the same day's post, Mr. Nasmyth wrote to Mr. Humphries, inclosing a
sketch of the invention by which he proposed to forge the "Great
Britain" paddle-shaft. Mr. Humphries showed it to Mr. Brunel, the
engineer-inchief of the company, to Mr. Guppy, the managing director,
and to others interested in the undertaking, by all of whom it was
heartily approved. Mr. Nasmyth gave permission to communicate his
plans to such forge proprietors as might feel disposed to erect such a
hammer to execute the proposed work,--the only condition which he made
being, that in the event of his hammer being adopted, he was to be
allowed to supply it according to his own design.

The paddle-shaft of the "Great Britain" was, however, never forged.
About that time, the substitution of the Screw for the Paddle-wheel as
a means of propulsion of steam-vessels was attracting much attention;
and the performances of the "Archimedes" were so successful as to
induce Mr. Brunel to recommend his Directors to adopt the new power.
They yielded to his entreaty. The great engines which Mr. Humphries
had designed were accordingly set aside; and he was required to produce
fresh designs of engines suited for screw propulsion. The result was
fatal to Mr. Humphries. The labour, the anxiety, and perhaps the
disappointment, proved too much for him, and a brain-fever carried him
off; so that neither his great paddle-shaft nor Mr. Nasmyth's
steam-hammer to forge it was any longer needed.

The hamme