528

Ewbank’s Siphons.

[Book V.

Contents of Standing casks. It would be better to make the dischargingleg of this sipbon of rather larger bore than tbe short one, since the rare-faction would then be rftore perfect. The discharging leg must alwaysbe inserted in tbe moveable tube before the short one is placed in theliquid to be transferred. (See Journal of the Franklin Institute for Julyand November, 1834.)

No. 267 is formed of a conical tube, and charged by the act of placingit in the fluid to be transferred. The end of the long leg is first closedtight by the finger, and the short one then immersed as deep as can beconveniently in the liquid. The air being thus confined prevents the liquidfrom entering, but when the finger is withdrawn, it is urged up the shortleg by the hydrostatic pressure of the column over the orifice of the latter,and the momtntum of the large volume contained in the lower part drivessufficient over the bend to put the instrument in Operation. The actionof this siphon depends upon the same principle as the spouting tubesdescribed in the last chapter. This siphon is in fact merely one of thesebent into a proper form. The bend should be a regulär curve in order topresent as little obstruction as possible to the liquid in passing over : itshould also be short, so as to require less of the passing fluid to fill it thana longer one. The proportions of the different parts of these siphonsshould approach those represented in the cut. Small siphons on this planare limited in their application to those cases where the short legs can beimmersed half their depth or more; but the application of large instrumentsincreases with the depth. (See No, 226 and remarks upon it, page 499.)

Nos. 268-9 are bloieing siphons, being charged by blowing with themouth through the tubes connected to the orifices of the discharging legs.This mode of producing a vacuum in one pipe by blowing air throughanother is sufficiently explained in a previous chapter. In No. 269, thejunction of the siphon with the blowing tube is flush or smooth in theinterior of the latter, and whenever this is the case a conical ajutage mustbe added as represented, or the instrument cannot be charged. (Seeremarks on blowing tubes, pp. 486-7.) The better way is to make thesiphon like No. 268, in which a part of the leg projects into the blowingtube and diverts the current of air from the lungs over the orifice, as inNos. 205—’6, ’7, and ’13. These are more readily charged than the others,and although they will operate without the conical ajutage, they are mucheasier charged with it. By such siphons water may be raised one or twofeet by a smart puff. They are safe and convenient to transfer acids, &c.as there is not the least danger of receiving any portion into the mouth,as when sucking siphons are used.

Siphons are now used, as they were by the Egyptians in Heron’s time,to convey water to considerable distances. When they are laid overground that is elevated from 20 to 25 feet above the spring, a quantity ofair is disengaged from the water at the highest parts of the tube, and accu-mulating there is very apt to cause the action to cease. To prevent this,a close vessel, furnished with a cock and funnel at the top, should be con-nected at its bottom to the highest part of the siphon by a stop cock orvalve. The air evolved from the water will collect in this vessel andshould be occasionally drawn off in. the following manner. Shut the lowercock and open the one attached to the funnel ; then expel the air by fillingthe vessel with water and turn the cocks as at first. As fresh portions ofair arise from the liquid, they will enter the vessel and drive the waterdown the discharging leg. When the ground is very uneven at thehighest parts, the several eminences of the siphon should be connected bysmall tubes to the air-chamber.