STE AM-B OAT THE subject of steam-boats has already been so am ply treated in a separate chapter of our article SIIIP numniNG, in p. 244 * of this volume, that very little remains to be clone under the present head.
The action of impelling boats by mechanical power was suggested and put in motion more than three centuries ago ;1- but the proposal to employ steam as the first mover of vessels was first made by Mr. Jona than Hulls in the year 1736, as we have already stated in the article Shipbuilding. The contrivance by which he proposed to produce this effect is shown in Plate DX. Fig. 1, which the author describes in the following words.
" Whereas several persons concerned in navigation, have desired some account of my invention for carry ing ships out of and into harbours, ports and rivers, when they have not a fair wind ; But I could not fully describe this machine, without writing a small treatise of the same, in which I shall endeavour to demonstrate the possibility and probabil ity of the matter undertaken.
There is one great hardship lies too commonly upon those who propose to advance some new, though use ful, scheme for the public benefit ; the world abound ing more in rash censure than in a candid and unpre judiced estimation of things, if a person does nut an swer their expectation in every point ; instead of friendly tretament for his good intentions, he too often meets with ridicule and contempt.
But I hope that this will not be my case ; but that they will form a judgment of my present undertaking only from trial. Hit should be said, that I have filled this tract with things that are foreign to the matter proposed, I answer, there is nothing in it but what is necessary to he understood by those that desire to know the nature of that machine which I now offer to the world : and I hope that, through thc blessing of God, it may prove serviceable to my country.
In some convenient part of the tow-boat, there is placed a vessel about two-thirds full of water, with the top close shut. This vessel being kept boiling, ratifies the water into steam. This steam being con veyed through a large pipe into a cylindrical vessel, and there condensed, makes a vacuum, which causes the weight of the atmosphere to press on this vessel, and so presses down a piston that is fitted into the cy lindrical vessel, in the same manner as in Mr. New
comer's engine, with which he raises the water by fire.
In Plate DX. Fig. 2, P is a pipe coining from the furnace to the cylinder. Q the cylinder wherein the steam is condensed. R the valve that stops the steam from corning into the cylinder, whilst the steam with in the same is condensed. S the pipe to convey the condensing water into the cylinder. 7'a cock to let in the condensing water when the cylinder is full of steam and thc valve p is shut. U a rope fixed to the piston that slides up and down the cylinder. This rope U, is the same rope that goes round the wheel D in the machine, fig. 1.
It hath been already demonstrated, that a vessel of 30 inches diameter, which is but two foot and a half, when the air is driven out, the atmosphere will press on it to the weight of 4 tons 16 hundred and upwards. When proper instruments for this work are applied to it, it must drive a vessel with a great force.
bigness of the machines may be propor tioned to the work that is to be performed by them ; but if such a force as is applied in this first essay, he not sufficient for any purpose that may be required, there is room to make such addition as will move an immense weight with tolerable swiftness.
It is my opinion, it will not be found practicable to place the machine here recommended, in the vessel itself that is to be taken in or out of the port, ke. but rather in a separate vessel, for these reasons : 1. This machine may be thought cumbersome, and to take up too much room in a vessel laden with goods, provi sions, &c. 2. If this machine is put in a separate ves sel, this vessel may lie at any port, Ste. to be ready on all occasions. 3. A vessel of a small burthen will be sufficient to carry the machine to take out a large one. 4. A vessel will serve for this purpose for many years, after she is thrown off, and not safe to be taken far abroad.