Page:Popular Science Monthly Volume 16.djvu/525

 funnel inserted in the neck of a flask. The method thus clearly portrayed is called destillatio per lacinias, and is evidently regarded as a process of distillation; ordinary filtration through porous stones and through bibulous paper is treated in another and following chapter.

Libavius makes reference to "Hippocrates's Sleeves," by which name were designated conical felt bags used in filtration.

Sir Robert Boyle, in his "Experiments touching the Spring of the Air," writes as follows: "Some learned mathematicians have of late ingeniously endeavored to reduce filters to siphons, but still the true cause of the ascension of water and other liquors, both in siphons and in filtration, [requires] a clearer discovery and explication." And in another place he gives this "explication": "The parts of the filter that touch the water being swelled by the ingress of it to their pores are thereby made to lift up the water till it touch the superior parts of the filter that are almost contiguous to them; by which means, these being also wetted and swelled, raise the water to the other neighboring parts of the filter till it have reached the top of it, whence its own gravity will make it descend."

These passages can only apply to anethisis, which was apparently a common method of filtration in Boyle's day.

Again, to trace this process still later, Juncker, in his "Conspectus Chemiæ," published in 1730, describes seven kinds of filtration. These differ chiefly in respect to the materials used: two methods, however, are essentially distinct; the one is styled "filtratio per chartam bibulam. . . in fundibulo vitreo" (filtration through bibulous paper in a glass funnel), and the other is described in the words "per segmentum panni lanei vel laciniam bombycinam vel funiculos gossypii" (through shreds of woolen cloth, silken threads, or through little strings of cotton).

Our friend Professor S. A. Lattimore sends us another reference to this process from "The Laboratory or School of Arts, etc., compiled by G. Smith, sixth edition, London, 1799" (vol. i., p. 435); the passage is as follows:

"To separate Water from Wine.—Put into the cask a wick of cotton, which should soak in the wine by one end and come out of the cask at the bung-hole by the other; and every drop of water which may happen to be mixed with the wine will still out by that wick or filter."

Thus we see that, so recently as the close of the last century, anethisis was accounted a practical method of filtration.