By this title I wish to distinguish this Ventilator from all such as act by the mere centrifugal force of the air: and to make this distinction the more palpable, I would add that this Machine acts like a pump, that is by means of a space alternately contracted and expanded, into which the air enters, and from which it is expelled by force as water is from a pump. The means are the following: A B ([fig. 4] of [Plate 20]) is a hollow cylinder, of a diameter proportioned to the effect wanted to be produced. C is a cylinder closed at both ends, which fills that just mentioned as far as the length goes, excepting a play of about 1⁄8 of an inch. This interior cylinder revolves in the former; but not on its own centre. It revolves on an axis E eccentric to itself, but exactly concentric with the outer cylinder A B. The centre therefore, of the inner cylinder C, describes a circle within the outer one, which is always parallel to its circumference. On the axis of motion of this cylinder C, and outside of that A B, are fixed two cranks E F [fig. 5], which exactly reach from its centre of motion to its centre of figure: so that whatever circle the latter describes in the large cylinder, the former describe the same line without it. And hence any slide or valve D, driven by these cranks, will always touch, or be equally near, the circumference of that interior cylinder C. The valve D then, worked by the bars G from without, forms a constant separation between the right and left hand parts of the lunular space left between the fixed and moveable cylinders; and if the latter turns from C by B to D, the right hand space C B G is the plenum, and the left hand space C A D is the vacuum of this Instrument; or in other words the air will flow in, through the passage H, and flow out through the passage I: and by a contrary motion of C, it would do the contrary—but I prefer the first process because any pressure within the valve D is not liable, then, to press the valve upon the drum C, and produce contact and friction; which in the second case it might do. Suffice it to add, that the quantity of air displaced at each revolution of C round its centre of motion, is the difference between the area of the drum C and that of the cylinder A B: and that its quantity at each part of the revolution is proportionate to the curvilinear triangle G B, multiplied by the length of either cylinder.
In the prospectus, this Machine was said to be good as “a gas meter,” which I still think it is. For such a purpose however, friction and eccentricity of weight should be obviated, by placing the axis E, in a perpendicular position: when I doubt not it would measure flowing gas better than many of the machines that have been proposed for that purpose.
OF
A COMBINATION OF WHEELS
To raise Water.
This mode of raising water in its simplicity, is I think called the Persian wheel. The buckets hang upon centres, dip in the under water, fill themselves there, and by meeting an obstacle above which turns the buckets aside, they empty themselves into the upper back, from which the water is conveyed to the general reservoir prepared for it. This present Machine is such an extension of the above principle as to make it applicable to considerable degrees of elevation, and to many situations where a single wheel would be of no service. Having observed that in every train of wheels, the circumferences of any two wheels, have motions towards each other, as well as from each other; I perceived that, in a vertical train, this circumstance might be laid hold of to compose a machine for raising water. Be therefore, ([Plate 21], [fig. 1]) A B C D four of a set of wheels thus intended: on the left of the lowest wheel the buckets move upward, as indicated by the arrow; while those at B move downward, coming thus to meet the former. The buckets A are full, and those B are empty; and as the latter, by the motions of the equal toothed wheels on which they are hung will infallibly meet the former, and even plunge into them at I K and L, it is only to put a clack of leather or a valve, in the bottom of all the buckets, and we have a machine that will raise water to the top-most wheel, be it ever so high, and there the water will be poured out into the vessel M, as in the common Persian wheel above alluded to. On this principle the first change of buckets will take place at I; where the lower bucket belonging to the wheel B G will take the water from the upper bucket of the wheel A H; when the bucket I will go down, nearly empty, by H and fill itself again in the under water; But the bucket of the wheel B G having now got the water, will rise by G to K, where another bucket belonging to the wheel C F will come empty, and plunging itself into that, take its water and go upward by way of C to L, where a similar change will take place and the water from L will rise by E to M, into which vessel it will be poured by the canting of the bucket as seen in the [figure]. Thus it appears that any number of toothed wheels geering together, surrounded with buckets valved at bottom, and receiving power from any one of their number, will raise simply and effectually a quantity of water not small in proportion to the power employed, and by means that promise great durability to the Machine.