In Fig. 10 the very same effect is produced by a wheel A, furnished with a number of vanes, in, a, d, which fall down on the circumference of the wheel at the side, and resume their other position by the action of a spring .c attached to each of them. They will consequently force up the water from D to C.
23. Description of Brown's Atmospheric Engine, ire which a vacuum is effected by burning oil or coal gas within the cylinder.
We have seen a model of a pump in which the air in the barrel was rarefied by burning the shavings of wood at the top of the barrel, an air-tight cap being put on when the rarefaction was supposed to be at a maximum. A certain quantity of water was thus raised above the valve at the bottom of the barrel, and the operation was repeated till the water rose to the desired height. Though this expedient might be found useful in cases of exigency, it bad not a sufficiently practical character, and we have not heard of its being introduced.
An analogous though totally different principle has been happily applied by Mr. Samuel Brown to create a vacuum in pumping engines, which may be employed both to raise water and drive machinery. The specification of the patent by which Mr. Brown has secured his right to this inven tion, was enrolled only in June, 1824, so that we are not able to speak of this invention on the authority of any actual trial of it on a large scale. The principle, however, of the invention is highly ingenious, and we are disposed to view it as a formidable rival to the steam engine in its best form.
In its general character of an atmospherical engine, Mr. Brown's invention resembles the steam engines of Savory and Newcomen, but the vacuum is effcted by burning coal or oil gas within the cylinder, so as to consume the atmospheric air.
The general appearance of Mr. Brown's engine is repre sented in Plate CCCCLXXI. No. Ill. Fig. I 1, where a and b are the two cylinders in which the vacuum is to be pro duced, c and d two rising mains leading from the reservoir i to the top of the cylinders a, b. Coal or oil gas is con veyed from a gasometer through the pipes e and J; the last of which passes into the cylinders, and terminates in the perforated burners g, while the pipe c terminates in small openings with sliders h h, in the side of the cylin ders a and b, immediately opposite to which are lateral jets, communicating with the burner g.
The reservoir i is filled with water, which, by passing through the pipe j into k, raises 'lie float /, and by pushing up the rod in, will elevate the end a of the beam nz. The cap a will thus be lifted from the cylinder b, and the brought down upon the cylinder a. By opening the stop cocks, the gas is to be let into the pipes c and f, and the jets at both ends of the pipe e, near h and /1, are to be set fire to. The slider h having been lifted by an arm g, moved by the ascent of the rod m, the flame of the jet e instantly communicates with the burner g, and causes it to burn within the cylinder. In the upper part of the apparatus, there is placed a small cylindrical glass vessel r, which is more than half full of mercury. It vibrates on pivots, and as the rod m ascends or descends, two small arms s, fixed to the rod ni, strike a pin on the side of the mercury ves sel, and thus raise and depress it alternately. The mercury being thus made to flow to the lower side, gives motion to certain minor parts of the engine, as will be afterwards explained.
In the position of r in the figure the rise of the end s of the vessel has by the rod t drawn the slider v over the mouth of the pipe j and closed it, opening at the same time the mouth of the pipe u. The water thus flows from i into so and into dd, forcing the float x to ascend and lift the rod y, which raises the end z of the beam, and takes the cap p from the cylinder a, while it places the cap o air tight on the cylinder b.
By this descent of the end n of the beam the rod m is brought down, which by the intervention of the arm y shuts the slider h. As the gas at g is now burning within the closed cylinder b, the air is consumed during the com bustion, and a vacuum produced. The water, therefore, rises, as in a pump in the main d, and flows over the top into the cylinder b, which is thus nearly filled, the rarefied air escaping through small valves in the top of the cylinder.