The obvious remedy was to invent some method, by which a block of iron should be lifted to a sufficient height above the object on which it was desired to strike a blow, and let the block fall down upon the work,--guiding it in its descent by 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.