SCIENCE NOTES.

Otago Witness, Issue 2057, 27 July 1893, Page 48

SCIENCE NOTES.

— A clever contrivance has been invented for the detection of small pieces of magnetisable metal, such as needles, tacks, steel, and iron chips, &c, that may have entered the human body unawares and*hidden themselves in the skin or deeper tissues. The instrument was devised by Dr J. B. Williams, formerly of San Francisco, and consists essentially of a partially astatic combination of small magnetic needles suspended within a glass tube, the tube being covered with tinfoil to mini-, mise electric action, except for a small space through which the needle can be observed. Ib is claimed that the instrument is sufficiently delioate to detect the presence of oneeighth of an inch of steel or iron wire at a distance of Gin from itself. Such an instrument will be of the greatest service in many cases where the ordinary methods of detecting the presence of foreign metallic substances are ineffective and unreliable. — Experiments in freeing potable water from micro-organisms have recently been described in a German technical paper. The inquirers first of all reported some previous experiments in the simple addition of alum to water, a single grain of this compound to a gallon of water reducing the number of organisms in 15 drops from 8100 to 80. Using larger quantities of alum, they were able to reduce the water to an absolutely sterile liquid. Another. experimenter has detailed his in-, vesiigations in the purification of water by sedimentation, and shows that during the storage of water in large reservoirs a natural bacterial purification takes place. Here is one of the results obtained :— Thames water before being admitted to the reservoir of one of the London water companies was. found to contain In every 25, drops 1437 microbes. These were reduced to 318. after the water had had time*to rest ; and after further rest in a second reservoir the number was reduced to 177. It has been long ago pointed out that the water of rivers undergoes a natural purification, and this, no doubt, is due to sedimentation. ' — "The day. is not far off when we will get heat and power without the intervention and' assistance of fire," said Civil Engineer Marston M'Grath to a St. Louis GlobeDemocrat reporter. ' "The solution will come when we get electricity direct from coal without the loss of any part of the wonderful energy that there is in the fuel. I never knew fully the value of coal as' a power-producer until I saw it exemplified on a recent trip across the Atlantic in the steamer -Majestic. The vessel carried 2400 tons of coal, almost enough to give a half busHel to every family in St. Louis, and it used up 290 tons a day to maintain a speed of about 23 miles an hour. This seems like an awful., lot of coal, 'doesn't it? But the Majestic is a big boat, 582 ft long, and it requires an expenditure of 18,000 h.p. to drive it at top speed through the water. Figure the thing oat, though, and you will see that l£lb of . coal, which is less than a good handful, furnishes 1 h.p, for one hour, and 1 h.p. represents the lifting to a height of Ift of 3001b; so that your, l£lb of coal lift 3001b lft and sustains it for one hour. Or take this illustration; It would require 100,000 galley slaves rowing night and day to carry the Majestic at a speed of 23 miles an hour. Dividing 18,000 h.p. into 100,000 galley slaves, we find that over 1 Jib of ooal represents the work for one hour of abont j six rowers. Of course there wouldn't be ! 'room for^the placing of more than 400 oars on the Majestic, and 10 bushels of coal would do an equal amount of work, while the 100,000 galley flaves, if they averaged 1501bs eacb, would weigh five times as much-as tbe 1740 tons of coal required by the Majestic for a six days' trip." — Some months ago, Mr Van der Weyde, tbe well-known London photographer, announced that he had invented a new apparatus, which he called the photo corrector, the object of whlcb was to diminish the Bize of the head,, hands, fo9t, or any other portion of a portrait, so as to correct any exaggeration which might easily be brought about by a too forward position of the sitter with respect to tbe camera. The' means he employs is a supplementary lens of peculiar construction placed within the camera, .close against the sensitive plate." This lens grasps, as it were, the light rays composing tbe part of the image needing correction, and while squeezing them into smaller compass, diminishes the size of the objecb. The idea' is most ingenious. ; — Pjofesßor Dixon's discovery a few years ago (writes a B.So. in the Adelaide Observer) that a trace of the vapour of water was absolutely necessary for various combustions in oxygen has been extended to quite a number of reactions; but tbe chemical world has hardly yet recovered from its surprise at the enormous importanpe in chemistry of mere traces. It was shown that carbon pould not be got to burn in perfectly dry oxygen, and now phosphorus— that most dangerously inflammable substance— can actually be distilled in perfectly dry oxygen. Of oouwe what the chemist calls perfectly dry oxygen can be prepared only by taking a lot of precautions. The strongest nitric acid, when perfectly pure,- becomes powerless to attapk metals, and so on. ' In a few years the question of chemical combination has taken an entirely different aspect. — The articles derived from the ooooanut palm, it is computed, can be put to some 300 separate uses. This is perhaps an overestimate, if to each article is only assigned one use, but as a matter of fact, in the makeshift circumstances in which many of the articles are employed, each of them has several uses, and the statement in this way is not so extravagant. Take, by way gf

illustratioMhe following list of derivations from the various parts of the, tree:— Every part of a house from roof to foundation, baskets; fans^ hats; bars; cpir-fibre, yielding mate, ropes, cables, brashes, brooms, bats, and " BtulfiDg „ for cushions and mattresses; goblets, spoons, lamps, and pipebowls; tooth-powder; lamp-black ;, combs ; candles; sweetmeats; palm oil; stearjne; arrack, distilled from the. sap ; tappa-cloth ; canoes; paddles; and, all kinds of barbaric weapons. Frava, from the meat of the ant ; an eye-wash from, the milk, which cures ophthalmia ; roots which serve the same purpose as the areca nut ; and an astringent medicine distilled from its fibres. The dethronement of steam, together with the great evils attending its, reign — smok.e' and grime — which would partially , be brought about by .the utilisation of electricity, would be still more completely effected by the realisation in practice of the magnificent scheme which is slowly but surely being developed in' scientific circles. Not only the metropolis) but most of the large manufacturing centres of the United Kingdom, will sooner or "later, become profoundly interested in this subjeot. The leading civil and electrical engineers advocate the establishment ; of large generating stations at the coalfields in Yorkshire, tiancashire,, and Staffordshire, where the. coal brought to the surface will be at once turned into fuel gas. , This gaa when employed in gas engines will furnish power to drive enormous dynamos, and the current from these dynamos .can be transmitted by overhead wires to any part of the kingdom. Arriving in London, for example, the electric current can be set to do all the work for which steam is now employed in factories, on. nilways, in street vehicles, or river boats. It is merely a question of. quantity, and the only limit to production likelj to be encountered is. in respect of the copper needed to form the.coil 9 of tbe electro-magnets in the dynamos.