"When the Weight, _G_, is so raised, while the wheels _Da_, _D_, and _Db_ are moving backward, the Rope _Fa_ gives way, and the Power of the Weight, _G_, brings the Wheel _Ha_ forward, and the Fans with it, so that the Fans always keep going forward, notwithstanding the Wheels _Da_, _D_, and _Db_ move backward and forward as the Piston moves up and down in the Cylinder. _L L_ are Teeth for a Catch to drop in from the Axis, and are so contrived that they catch in an alternate manner, to cause the Fan to move always forward, for the Wheel _Ha_, by the power of the weight, _G_, is performing his Office while the other wheel, _Hb_, goes back in order to fetch another stroke. "_Note._ The weight, _G_, must contain but half the weight of the Pillar of Air pressing on the Piston, because the weight, _G_, is raised at the same time as the Wheel _Hb_ performs its Office, so that it is in effect two Machines acting alternately, by the weight of one Pillar of Air, of such a Diameter as the Diameter of the Cylinder is." The inventor suggests the use of timber guards to protect the wheels from injury, and, in shallow water, the attachment to the paddle-shafts of cranks "to strike a Shaft to the Bottom of the River, which will drive the Vessel forward with the greater Force." He concludes: "Thus I have endeavoured to give a clear and satisfactory Account of my New-invented Machine, for carrying Vessels out of and into any Port, Harbour, or River, against Wind and Tide, or in a Calm; and I doubt not but whoever shall give himself the Trouble to peruse this Essay, will be so candid as to excuse or overlook any Imperfections in the diction or manner of writing, considering the Hand it comes from, if what I have imagined may only appear as plain to others as it has done to me, viz., That the Scheme I now offer is Practicable, and if encouraged will be Useful." There is no positive evidence that Hulls ever put his scheme to the test of experiment, although tradition does say that he made a model, which he tried with such ill success as to prevent his prosecution of the experiment further; and doggerel rhymes are still extant which were sung by his neighbors in derision of his folly, as they considered it.