SCIENTIFIC.

New Zealand Herald, Volume XI, Issue 3824, 13 February 1874, Page 3

SCIENTIFIC.

Mn. L. V. Lavees writes to tho Sydney Morning Lleruld, Buggering what he describes as u pltm, simpl'J and inexpensive, but very eflicacious, for filtering. It maUes tho foulest water clear, unci is procurable by the poorest. It is, I beliovo, generally known that a thread of cotton or worsted suspended in liquid will have tho effect of a syphon, mid speedily empty the vessel containing it.; but it does not appear so gonerally to have occurred to other minds, as it hns from practical experience to mine, that the so called syphon will at the same time perform the office of a filter. This however, it certainly does, and the reason appeire to mo to be simply this: —The water on liquid necends the thread by means of capillary tubes. These tubes in some instances are infinitely minute, and. causo tho liquid to ascend in globules almost as small us those which conetitulo steam or vapour. I need scarcely refor to tho fact that unless severs globules are chemically united in a liquid all organio matter foreign to tho two gases which constitute eaeh globule must necessarily lodge between the interstices ; therefore anything at all analogous to evaporation or distillation must have tho effect of separating all organic matter held in suspension, such as lead, crease, etc. I have had for several days a filter of this kind constantly at work. It is nothing more than a balf pound of white worsted cut into lengths of about a foot, an t suspended all around » tub or veesel placed under the water tap and on the top of the wator-cosk. ihetap ie of course, regulated to ihe exact discbargo of these eo-olled syphons, and I find that this half pound of worsted will filter in twentjrfour hours upwards of 25 gallons. Xhue a very efficient filter can bo produced at the small outlay necessary for the purchase of hal a uound of worsted s but listing or any other woollen material out into strips of a similar length will answer tho purpose equally well. I havo mentioned this to several scientific gentlemen, including our city health officer, Mr. Dausey; they on and all approve of my theory, and I now take liberty of asking the use of your columns to make the matter generally known, and then for the future any individual resident who can procure a water-cask or smaller vessol and a few ehrede of woollen may thank himself if be drinks impure or poisoned water.