FILIGRANE WORK, or FILAGREE WORK, from Inum and granum, is the name given to a kind of ornamental work, in which flowers, Sze. are formed of fine gold and silver wire, curled or twisted in a serpentine form, and some times plaited, and worked through each other, and solder ed together.
This art appears to have been brought to Europe from the East, and has been occasionally employed in all ages. Such of our readers as take any interest in the subject, are referred to the following works, quoted by Beckmann in his History of Inventions, vol. ii. p. Haiie's ll'crkstate der kiinste, i. p. 101 ; Jacobson Tecti nologisches Ilrorterbuch. i. p. 721; Grignon Bulletin des fouilles d'unc ville Romaine, i. p. 22. ; Menage Dictionnaire Etymologique, i. p. 597 ; J. H. Jungius Disquisit. de Reli gulls ; accedat Lipsanographia sive Thesaurus reliquiarum Electoralis Brunsuico-Lutieburgictis. Ilanov. 1783, 4to. p. 19, 29, 56. Marsden's History of Sumatra, Lund. 1783, p. 145. Der Mistress Kindersley Bricle van der Insel Te nerifira and Ostindien, Leips. 1777. Thomans Lebensbe.schreibun,q, Augsh. 1788 ; and Von Stettcn Kunsl geschichte, i. p. 489, and ii. p. 287. (w) Fla.TER, is an apparatus employed to clarify impure wate for domestic purposes; and it is also used in many arts, to separate the impurities from other fluids. A filter acts as a sort of sieve or strainer, having innumerable small passages through which the fluid can percolate slowly ; but as the passages are not sufficiently large, to allow the par ticles of matter which are mixed with the fluid to escape, they are detained by the filter.
All springs of water which we are accustomed to call pure, are only rendered so by the effect of natural filtration ; for the rain falling upon the surface of the earth, soaks first into the vegetable mould with which the surface is al most every where covered ; in passing through this, it takes up not only dirt or earthy particles, but the remains of vegetable substances, which are in the progress toward decomposition; the water is thus rendered turbid and un wholesome for domestic purposes : such is the state of the waters of most rivers which are not supplied by springs alone, but by brooks running on the surface. That portion of the water which soaks into the earth having passed through a sufficient thickness of porous strata, eitherby as cent or descent, will have all extraneous mixtures detained, and become clear spring water. It should be observed, that filtration can only produce transparency, by arresting such particles of matter as are in a state of mechanical mixture with the fluid, for any matter which is held in che mical solution in the fluid will pass with it, through the pores of the most minute filter, unless the substance of the fil ter itself should have a greater affinity for such matter than the fluid which contained it. In this case, a new combina
tion will be formed, and the matter in solution, leaving the fluid, will be taken up by the filter, not simply because the passages are too small to permit its particles to pass, but on account of the superior elective attraction between the substance of the filter and the dissolved matter.
Filtration, on this principle, cannot continue to produce a natural spring for any great length of time ; because, by the constant addition of matter, the filter will at last become saturated with it, or choaked up. In applying this reason ing to springs, we shall find a reason why so few springs produce pure water, although it is always transparent. In reality, the great natural filters which produce springs, are almost always on an opposite principle, viz. that the sub stance which composes the filter has a great affinity for the water, and its particles are thereby taken up slowly in so lution, and carried of at the same time that the extrane ous matters, which are only in mixture with the water, are detained in the pores of the filtering strata : thus we find springs which have not some mineral held in solution by the water, although invisihle to the eye; and in cases where heat is generated in making the new combination we have spoken of, hot springs will be produced. The most common mineral taint which water receives in its natural filtration, is sulphate of lime or plaister of Paris : this ren ders the water hard, as it is called, so that it will not pro duce a lather with soap, but curdles it. Sulphate of iron or vitriol is also frequent in springs. Add to this, that in great towns, the drainage water which soaks into the earth is contaminated by animal matters as well as vegetable, and in such an offensive state, that the filtration through the soil can scarcely restore its purity. From all these causes, it is found that the turbid and foul waters of rivers, where altered by art to separate from their extraneous mix tures, will be more pure and wholesome as a beverage, than the generality of spring water.