It is not solely because, to work with the feet is a good method of employing the strength of men, that this device is presented to the mechanical public; but it is with the view of so employing the feet and hands, that they may occasion a constant and equable flow of water. The means, (see [Plate 44], [fig. 1]) are, to provide the man with two supports a b for his hands, and two pedals c d for his feet, by which the two rods e f are worked; and by them, through the cords or chains g h, the piston rods i and k. Of the latter, the one which answers to the lower pump l, goes through the upper piston, whose rod is i: and the pistons are both constructed in the manner shewn in [fig. 2]; that is to say, the piston has no body, fitting the pump barrel: but a triangular bar x, going diagonally across the pump barrel, (which is square) and carrying two wings or valves y z; which, both together, fill the barrel when down, and leave it as empty as possible when up, by which motion the chains a e are slackened. Further, these pistons, with their rods, are heavy enough to raise the pedals, the instant the man raises his feet in any degree: so that, by a proper combination of the motions of his hands and feet, he can let down a given piston, and begin again it’s ascending motion before his effort has wholly ceased on the other pedal. A mean this, of producing a constant and equable rising motion in the column of water through the pumps k l; and a mean also, of doing more work with a given fatigue, than would be possible in a pump whose motions were merely reciprocal, and the water of which, in rising, would be subject to any unequable or convulsive motions.
In general, this portable pump was made (many years ago) with a view to being easily carried to any field or garden, bordering on a river, and worked on it’s bank; the flexible suction pipe p being thrown into the river, or a well, as occasion might require. To this end, the whole frame (as is evident from the figure) can be folded up into a kind of faggot: and thus it’s transport from place to place, be made perfectly commodious.
OF
THE BISECTING COMPASSES.
It often happens, that from a central line, (in drawing for example) we want to set off, quickly, many equal distances on each side; or between two given lines we want a central line; to perform either of which operations, is the use of the Instrument just mentioned.
It is represented in [Plate 44.] [figs. 3 and 4], where A B is the central point, being cylindrical in the greatest part of it’s length, and conical at E B. It slides correctly in two cannons or swivels E & A, which also have two short axes or trunnions, on which first, the double compass joints C D turn; and second, the two pairs of arms F G. I have called these cannons, swivels, that I may shew their construction, by referring to [figure 1] in [Plate 30]—which describes the swivel of the [forcing Machine]; and which will give a complete idea of what is here intended. From this construction it will appear evident, that the point A B, ([Plate 44]) will be always found in the middle, between the two points, of the outer legs of the compasses; and that whether the question is to take two equal distances from a central point, or to bisect a given line or distance at one operation. The point or style now slides in the two swivels A and E; but the Instrument might be so constructed, as for it to follow the rising motion of the middle joint (E), and thus to keep the three joints in the same horizontal line: but I think a small perpendicular motion of the said style, would be always desirable in the Machine, as a drawing Instrument.