SCIENCE NOTES.

Otago Witness, Issue 2451, 6 March 1901, Page 62

SCIENCE NOTES.

M. Meroier, of St. Aubin dv Coudrait, de•tcribea one of the most singular fishing devices imaginable. The system, although of ' extreme simplicity, is somewhat revolution'*ry, and was discovered by chance. A pond 'on the farm of La Marlequette, bordered by ' rocky shores, had never been drained, _ owing to the expense. Last year the proprietor 'conceived the idea of making use of a powerful steam-pump; . . . Each stroke of the piston drew up a hectolitre (25gal) of water, and the pond was therefore emptied in a few hours, and not only was the water drawn t>ut also all the fishes that it contained. This was a revelation. All the owners of ponds in the neighbourhood have at once followed suit, and the owner of the pump is making a specialty of this kind of work. He lets out one of his pumps, modified for this purpose, and the peasants of the region call it "the fish-pump." Each stroke of the {piston brings up a torrent with which are mingled fish and crawfish, together with dirt and debris such as are contained in every pond (old sardine boxes, etc.). A sort of metal basket receives the whole. The water and slime escape, while a boy collects the fish and sorts them according to species and ■weight. Hecently, in ten hours, the fish in a pond of several acres have been withdrawn at an expense of 36 francs. The process is curious and ingenious, and is probably especially adapted to bring about the extinction of the fish tribe. — Cosmos (Paris) .

— Owing to the generosity of the Emperor of Austria, Herr Wilhelm Kress, who first began to work upon his aerial machine some 20 years ago, will now be enabled to complete it. His idea is to support Kis " ship " with the help of great wings of silk or hemp expended by means of steel ribs resembling the spokes of a bicycle wheel. These would in themselves act as parachutes, and allow the car beneath to descend gently. This car or boat rests on runners like those of a sledge, which would enable it to glide on ice, snow, or grass, and the boat itself would sit on water. The machine is to be raised and moved by two propellers similar to a ship's screws. These, while propelling the vessel, will make the wings or sails face the air. With these latter, or part of them, directed apwards, a power will come into action which will (says the Vienna correspondent of the Daily News) first support the weight of the boat, and then raise it in the ak as it grows stronger. Ihe screws are to be set in motion by a benzine motor of 20-h.p.. and of exceeding lightness. It is believed that it will not weigh more than from eight to ten kilograms per horsepower, and will be made of aluminium. Herr Kress, to set his model in motion, uses mdiaTubber springs, and though the little machine never "flew" longer than a matter of minutes, the experiment, however often it vras repeated, always succeeded. The inventor, who attended the technical schooh to >-tivly machine construction \vh n he was almost 50, hopes that the fir&t experiments with bia full-

sized air-ship will be made in the spring. He calls his invention "Dragon-flyer."

— Arsenic is an element so widely diffused in nature that one difficulty in testing for it rests on the fact that it is extremely difficult to obtain sufficiently pure materials for use in testing, while other difficulties arise, because many arsenic compouifds (among which may be mentioned the very common arsenio aedd) often fail to respond to such tests as are relied on by the more superficial practitioners. Now that the salts of cacodylic acid and, possibly, salts of other organic derivatives of arsenic, are used medinically, the question of testing for arsenic has become one of the most difficult tasks in analytical chemistry. Still, in the recent newspaper controversies some persons have very truly remarked that testing for arsenic is so simple and easy that any jschoolhoy can test. It is this ease of testing which is the source of danger, and in such a case the presence or absence of arsenic in the substance tested will generally have no influence on the result of the test. Even the eminent toxicologist, Dr Alfred Swaine Taylor (who, by the by, was one of the pioneers in photography, and the author of a handbook of photography, published as early as 1840), once made a serious mistake in an important case, the arsenic he detected having been in the copper which he used. Our experience of the delicacies and difficulties of testing for arsenic goes back to the time when Dr A. S. Taylor devoted a course of lectures to this subject ; and, as part of that essential preliminary to actual tests, the getting together of materials and apparatus free from arsenic, we have from time to time noted the presence of really large quantises of arsenic in man} articles and cheni'oals which are in every day use by photographers. A list is out of the question, but we may give a dozen examples. I'erchloride of iron, glycerine (as much as 2.5 per cent.), alum, sulphate of iron, a yellow indiarubbe. air ball and tube (over 6 per cent.), sulphuric acid, hydrochloric acid, phosphate of soda, celluloid (milk-white, yellow, green), an indiarubber cork, white flintglass, blaok gummed paper. In a recent issue of Engineering we read of sulphurio acid in which the arsenic rises to 5 per cent., which would be nearly 2oz to a pint ; and as so many chemicak are manufactured by the aid of sulphuric acid, the widespread presence of arsenic is scarcely to be wondered .at in such "beers" and "wines" as are laboratory products. Natural food stuffs are remarkably free from arsenic, as both plants and animals almost always reject the poison. If arsenic is added to flour paste, an arsenic evolving mould will often appear. — Amateur Photographer.

—In marine warfare (says L'Electricien, Paris) all vessels are provided with electric searchlights, whose use is of the greatest service. The military uses of electricity are taking on new importance and new extent, at the present moment, bj its application to coast defence. To assure the better protection of the coast from Villefranche to Toulon, it has been decided to establish special electric posts, intended to reveal the enemy's presence, in cases of an attempt at a night attack, by powerful electric beams, which will light up the country to a great distance, will sweep the horizon, and thus, while preventing a surprise, will guide the aim of the land batteries and increase their accuracy. The work of these stations is now being pushed with the greatest activity. They are a kind of blockhouse, built very solidly of cement, stone, and concrete, six to seven metres (20ft to 23ft) high, forming a single piece in which a revolving mount, operated by a hydraulic motor, supports the reflector of the searchlight, which has a power of projection varying from 15 to 18 kilometres (nine to 11 miles), and is raised 1.3 metres (4ft 3in) above the masonry platform. The energy is produced by a dynamo of 80 to 100 volts operated by a steam engine in a little engine house near by, and is transmitted by special cables One of these stations has already been erected west of Nice, and others will soon be completed, notably at Golfe, Juan, Beaulieu, and in the citadel of Villefranche whose fine roadstead already has its approach protected by two similar stations. — There is a metallic alloy invented and patented in Germany to take the place of gold, which, even if exposed for some time to the action of ammoniacal and acid vapours, does not oxidise or lose its gold colour". It

can be rolled and worked liko gold, and has the appearance of genuine gold without containing the slightest percentage of that metal. It is much cheaper than other compounds and alloys used as substitutes for precious metals. The alloy consists of copper and antimony in the approximate ratio of 100 to 6 and is produced by adding to molten cop per, as soon as it has reached a certain degree of heat, the antimony. When the antimony has been thoroughly diffused with the copper, charcoal ashes, magnesium and limespar are added to the mass when the latter is still in the crucible. The action of this material admixture of flux is not explained, but the alloy loses thereby a certain porosity otherwise present and greater density of the cast metal is obtained. — In the petroleum-bearhig districts, as at Baku and elsewhere, a combustible gas is produced naturally, and is used in the districts for illuminating and other purposes. Several systems have been devised for producing this gas artificially by passing air over petroleum pf a similar spirit, and Dr J. A Purves has recently described some simple forms of apparatus by means of which this is accomplished. The simplest and most efficient apparatus depends upon the fact that air containing the vapour of petroleum or other hydrocarbons is heavier than ordinary atmospheric air. It consists essentially of a tall metal vessel, having an opening at the top and another near the bottom. The apparatus is filled inside with wood pulp saturated with petroleum. Air enters at the top of the vessel, and takes up a certain proportion of the vapour of the spirit. The air thus becomes heavier and gravitates through thtj remainder of the absorbent material, taking up more and more of the vapour, until it finally issues from the lower orifice in the form of a gas capable of lighting, heating, and all other uses to which ordinary gas can be put. As the wood pulp or other absorbent used is practically solid, there is no danger either from the presence of loose petroleum or of explosion. The light is of high illuminating power and of remarkable purity, so it has a wide sphere of usefulness. — Leisure Hour for January.

— The trains which are now running over the section of the Trans- Siberian from Moscow to Irkutsk are provided with a complete electric system which serves for the lighting and heating of the cars, as well as for the water and milk heaters in the dining car. In the baggage car has been placed an installation consisting of a boiler, a steam turbine, and a dynamo of 5-h.p., which gives the current at a tension of 65 volts; the plant is under the supervision of an engineer appointed for the purpose. Under one of the cars is disposed a' battery of accumulators, which assures the lighting for four hours in case an accident should happen to the dynamo plant, and the latter may be stopped during the night when only a few lamps are in use. Electric cigar-lighters are placed in each compartment.

— The already practically foreshadowed widening use -of aluminium conductors for electric transmission purposes adds interest to Lord Kelvin's recently expressed opinion of them. The weight of aluminium required, hs aaid, ie almost exactly one-half of the copper which would produce the same effect. The diameter of cable is 28 per cent, in excess of one made of copper, and the cost of insulation for an underground cable is increased in about the same proportion when we pass from copper to aluminium. Aluminium is not a pleasant metal to deal with, but its high conductivity will make it invaluable for overhead transmission. It is true also that the weight to be supported on posts is half of copper, but the surface exposed to the wind is greater, and its strength is not great. The chief drawback to its use, especially overhead, is its liability to become rotten. This defect does not exist if the metal be pure, and especialy if free from sodium. But exposure to atmosphere, especially near the sea, induces deterioration. The fact that aluminium I« easily oxidised ought not to condemn it. The same is true of iron and steel, and yet we do not hesitate to place structures of these metals in exposed positions. Only we paint them; so Lord Kelvin proposes that we paint or varnish aluminium conductors wherever necessary.— From Cassier's Magazine for December.