In nearly all seagoing vessels, the Paddle has now almost entirely given place to the Screw. It was long before this invention was perfected and brought into general use. It was not the production of one man, but of several generations of mechanical inventors. A perfected invention does not burst forth from the brain like a poetic thought or a fine resolve. It has to be initiated, laboured over, and pursued in the face of disappointments, difficulties, and discouragements. Sometimes the idea is born in one generation, followed out in the next, and perhaps perfected in the third. In an age of progress, one invention merely paves the way for another. What was the wonder of yesterday, becomes the common and unnoticed thing of to-day. The first idea of the screw was thrown out by James Watt more than a century ago. Matthew Boulton, of Birmingham, had proposed to move canal boats by means of the steam-engine; and Dr. Small, his friend, was in communication with James Watt, then residing at Glasgow, on the subject. In a letter from Watt to Small, dated the 30th September, 1770, the former, after speaking of the condenser, and saying that it cannot be dispensed with, proceeds: "Have you ever considered a spiral oar for that purpose [propulsion of canal boats], or are you for two wheels?" Watt added a pen-and-ink drawing of his spiral oar, greatly resembling the form of screw afterwards patented. Nothing, however, was actually done, and the idea slept. It was revived again in 1785, by Joseph Bramah, a wonderful projector and inventor.[5] He took out a patent, which included a rotatory steam-engine, and a mode of propelling vessels by means either of a paddle-wheel or a "screw propeller." This propeller was "similar to the fly of a smoke-jack"; but there is no account of Bramah having practically tried this method of propulsion. Austria, also, claims the honour of the invention of the screw steamer. At Trieste and Vienna are statues erected to Joseph Ressel, on whose behalf his countrymen lay claim to the invention; and patents for some sort of a screw date back as far as 1794. Patents were also taken out in England and America--by W. Lyttleton in 1794; by E. Shorter in 1799; by J. C. Stevens, of New Jersey, in 1804; by Henry James in 1811--but nothing practical was accomplished. Richard Trevethick, the anticipator of many things, also took out a patent in 1815, and in it he describes the screw propeller with considerable minuteness. Millington, Whytock, Perkins, Marestier, and Brown followed, with no better results.