Page:Popular Science Monthly Volume 16.djvu/523

Rh anethisis, a word made from ává, "upward," and ᾖθισις, "a straining off." A study of the chemical works of the middle ages further shows that the expression "destillatio per filtrum" is invariably used to describe anethisis, while "filtratio" is applied to ordinary filtration. We shall give quotations proving this, but first make brief reference to early records.

The ancient Egyptians portray in the rock-cut memorials the operation of filtration in connection with the manufacture of wine. Their simple wine-press consisted of a bag in which the grapes were placed, and squeezed by means of two poles turned in contrary directions. Small colanders of bronze have been found at Thebes. Views of the interior of an Egyptian kitchen, cut in the tomb of Rameses III. at Thebes, represent siphons in use for drawing off liquids of various kinds. (Wilkinson.) The ancient Romans employed strainers and colanders (colum) made of a great variety of materials. Wine-strainers were made of silver and bronze; the poorer classes used linen, and, where nicety was not required, they used those made of broom or of rushes. Strictly speaking, however, percolation through colanders is not filtration, for capillary action plays no part.

It is interesting to note that the earliest mention of filtration which a brief search has disclosed refers to the method we have ventured to call anethisis. This occurs in Plato's "Symposium," written about four hundred years before the Christian era; the passage is as follows: "Socrates then sitting down, observed, 'It would be well, Agatho, if wisdom were a thing of such a kind as to flow from the party filled with it to the one who is less so, when they touch each other, like water in vessels running by means of a thread of wool from the fuller vessel into the emptier.'"

Aristotle, the pupil of Plato, in his essay "De Generatione Animalia," refers to the other process in the following words: "Flesh is produced, therefore, through the veins and pores, the nutriment being deduced in the same manner as water through earthen vessels not sufficiently baked."

This passage, together with others occurring in Plato, shows that both systems of filtration were employed at that early period.

Geber, whose clear description of anethisis we have quoted, was followed by the celebrated Arabian physician, Rhazes; he uses the same expression, "destillatio per filtrum," in the following passage: "Dissolve as much [common salt] as you wish in five times as much warm soft water, and distill per filtrum and congeal [i. e., crystallize]." Rhazes died about 930

Among the early writers on alchemy, no one is oftener quoted than Raymund Lulli, surnamed the Enlightened Doctor (born 1235, died