414 Hot water raiseä by Steam in soap manufactories. [Book IV.
hundred gallons of ley, with the other ingredients, tallow, rosin, lime, &c.are put. After the whole has been several times boiled, the semi-fluidmass is suffered to remain some time at rest, when the ley collecting at thebottom leaves a thick stratum of soap formed above. As no openings aremade in the sides or bottom of the boiler, the hot ley is drawn off at thetop, and is usually done by a common pump. Long after the fire is with-drawn steam c'ontinues to rise front the liquid below ; for, from the vastmass of heated materials, their non-conducting property, and that of thefurnace, the heat is slowly dissipated. The soap in the mean time acquiresa firmer consistence, and prevents the vapor from escaping above almost aseffectually as the bottom of the boiler does below; so that not until thesteam attains considerable elastic force can it open a passage through,and when it does the opening is instantly closed as before. When there-fore the pump is pushed through the whole to the bottom of the vat, andstarted to work, the liquid continues of itself to pass up, being urged bythe steam. (It is necessary to work the pump at first because the open-ings in its end become stopped with soap in passing it down. The endof a plain tube would be choked in the same way ; but by a pump at-tached to it, the pressure of the atmosphere is added to that of the steamto force the passage open.) The large body of soap keeps settling downas the ley is discharged, and thus preserves the steam at the same degreeof tension until all the ley is ejected, when the steam itself escapes alsothrough the pump. The soap, it will be perceived, acts as a flexible pis-ton, its adhesion to the sides of the boiler and its spissitude and weighteffectually confining the vapor below.
Of the origin of this mode of raising ley, and the extent to which it ispracticed, we are not informed. It affords however an example of thetruth of the remark, that important results may be deduced from attentionto simple facts, as well as from the observance of common products. Anexamination of the residuum of a soap-boiler’s kettle, it is well known, ledto the discovery of a new Chemical element, (iodine,) and of its virtues asa specific in the eure of the goitre ; and from the preceding remarks it maybe inferred, that an observing Greek or Roman soap-boiler might havediseövered the applicability of steam to raise water, since he possessed allthe requisite machinery in his ordinary apparatus, and might have per-formed the Operation as often as he made soap. His ingenuity would alsohave been rewarded by a diminution of his labor. And who can provethat such a plan was not in use in some of the old soap-factories of formertimes 1 In that, for example, which has been diseövered in Pompeii , inone apartment of which are the vats, placed on a level with the ground,and in another were found heaps of lime of so superior a quality as tohave excited the admiration of modern manufacturers.®
Of the manipulations of ancient mechanics and manufacturers we knowlittle or nothing. Of the thousands of their devices, many väluable öneshave' certainly been lost. Some of these have been revived or rediscovöredin modern times, among which we think may be mentioned various appli-cations of steam. There were indeed so many occasions for the enlploy-ment of this fluid by the ancients, and particularly in raising of water, that,taken in Connection with the information respecting it in the Spiritalia, thepart it was made to perform in the temples, the traces of it in the hot