[Fig. 9, 10 and 11] of [Plate 17], represents one of the forms of this equilibrium Cock. It consists of a square plug case or chamber a b, with a hole c d bored transversely through it, exactly across its centre: and to this chamber is fixed by the flanches e f, the bifurcated water-passage g h, forming one body at i. The plug of this instrument admits of various forms and proportions; of which I have shewn two in the [figures 9 and 11]. The first m n, receives the fluid through the two openings c d, which correspond, in one position of the plug, with the double water-passage before mentioned. And further, the plug itself is bored lengthwise in its under end n, so as to form the spout of the cock: or otherwise (see [fig. 9]) this spout is taken in a double form from the outer surface of the plug at b a, so as to present two streams, thus producing, I think, an instrument of somewhat greater solidity. All that seems important is, that whatever be the pressure of the fluid from without, it be made equal on both sides of the plug, so as to occasion no friction between it and the chamber. The principle is indeed so effectual, that one might distribute steam pressure of the greatest strength or even gunpowder pressure, without much resistance to the operator, and without injuring the mechanism by oft repeated action.
OF
A MACHINE
To communicate and suspend Motion.
In [Plate 19], [figs. 3 and 4], shew this mechanism in two directions. It is composed of two wheels C D, cut (or cast) into teeth of a peculiar kind, that both geer with one another, and at the same time, include the chord or round strap A B, by which they are driven. These teeth can be better represented by a figure than in words; and will I suppose be understood from [figures 3 and 4]: They are divided, on the rim of each wheel by a space too small to admit a tooth of the other wheel: but then, every-other tooth is cut away in a sloping direction on each side of the wheel, from the bottom of the tooth to its top on the opposite side: so that while these teeth are working in each other they offer two grooves, in the form of a V, which coming together surround the chord and press it in four points, either to drive the wheels by the cord, or to pull the chord by the wheels, according to the use it may be wished to make of this mechanism. In [fig. 4] the cord is seen at A B, passing among the teeth of the wheels; and in [fig. 3] it is shewn at C, as a mere circle, in the centre of a lozenge formed by the teeth whose points now geer together. [Fig. 5] is a sketch belonging to this subject, which shews something of the manner of using this round strap as a mover: for by carrying it (either in a horizontal or vertical plane) by a line slightly curved, from one machine to another, it will drive them all and give the means of stopping any one at pleasure. Suppose then, A B C D [fig. 5], to be four machines placed as above mentioned. If I wish to stop the machine B, I merely draw back the pressure wheel E, and the cord ceases to lay hold on the machine as shewn by the dotted line: but when I want to set it on again, I do it by bringing back the wheel E to its present position. And thus at a small expence, I could geer a considerable factory, in a way which I think as durable as it appears economical. The principal objection, perhaps, is that this cord is liable to wear out soon, by such incessant action; but then the pressure on it needs not be great; and of friction properly speaking there is very little: Besides which, the cords would be made of a peculiar texture, perhaps of leather, sewed edge to edge and covered like a whip, by one of the machines I shall bring forward [hereafter].
