In 1770, Watt wrote to Dr. Smalls (who, a Scot, was at one time a professor at William and Mary College, in Virginia, but returned to England in 1785) regarding the latter’s experiments in relation to canal navigation, asking him, “Have you ever considered a spiral oar for that purpose, or are you for two wheels?” In the letter is the sketch, a fac-simile of which is here shown: [Illustration: Sketch of spiral oar] Dr. Smalls answers that, “I have tried models of spiral oars, and have found them all inferior to oars of either of the other forms” (Muirhead’s “Life of Watt,” p. 203). Joseph Bramah, in 1785, took out a patent for propelling vessels by steam, wherein, after describing the method figured in his specification of using a wheel at the stern of a vessel, in which he places the rudder at the bow, he proceeds as follows: “Instead of this wheel A may be introduced a wheel with inclined fans, or wings, similar to the fly of a smoke-jack, or the vertical sails of a wind-mill. This wheel, or fly, may be fixed on the spindle C alone, and may be wholly under water, when it would, by being turned round either way, cause the ship to be forced backward or forward, as the inclination of the fans, or wings, will act as oars with equal force both ways; and their power will be in proportion to the size and velocity of the wheel, allowing the fans to have a proper inclination. The steam-engine will also serve to clear the ship of water with singular expedition, which is a circumstance of much consequence.” Bramah thus very clearly describes the screw, and in so doing must unquestionably be numbered as one of the many fathers of this system of propulsion. Fitch, as before stated, is recorded, on most trustworthy evidence, to have been another: and Mr. Stevens, of Hoboken, not only carried out successful experiments with the screw in 1804, at New York, but even experimented with twin screws. Charles Cummerow, “in the City of London, merchant,” patented, in 1828, “certain improvements in propelling vessels, communicated to me by a certain foreigner residing abroad,” in which the screw is set forth in a manner not to be questioned. Who the “certain foreigner” was, who communicated the invention to Mr. Cummerow, has not come down to us. It had, however, like the steamboat as a whole, to wait for a certain preparedness in the human intellect. Invention knocked hard, and sometimes often, in the early years of the century, before the doors of the mind were opened to receive it; and too frequently then the reception was but a surly one, and attention deferred from visitor to visitor until one came, as did Fulton, or Ericsson, who would not be denied.