SCIENCE NOTES.

Otago Witness, Issue 2375, 7 September 1899, Page 54

SCIENCE NOTES.

— The use of jjectrie wavet in Marconi's j gystem of space telegraphy lends interest to j -a newly-discovered deteefcoi of such waves, ■ which may possibly prove a ival to the '■ "coherers" aow used as receivers in this; system. The jevice, whioh is the invention . »f Dr Neugschwerfdei , is thus described in the Electrical Review; — " If a scratch is made in the silver coating of a mirroi so as to di^ ♦ride the coating into two oarts insulated from one anothe. , then, of "course, no current will pa^s when the two piuib ai-u i"jii iaected to ihe terminals of a cell of battury If thte gap ir. the mirror coating is breathed tiyon, there will be a deposit of moisture.

and some current flows, which will be detected by a galvanometer in the circuit. Under the&e conditions, if electric waves are generated in the neighbourhood, the galvanometer, if its sensitiveness is not too great, goes back to zero, showing that the impact of the waves has made the resistance of the gap very great. Breathed upon again, the gap becomes conducting, and the galvanometer again shows a deflection. If a damp cloth is laid over the gap so as to maintain a constant supply of moisture, the galvanometer goes back to zero only while the waves are impinging upon the gap. Copper and zinc mirrors work as well as silver, and other good insulating materials may be used instead of glass as a base for them. Instead of water vapour, ammonia, and salt solutions may be used with equal success "Mechanical vibrations, sound waves, heat, and static electricity seem to have no influence upon the conductivity, but even small sparks have a marked effect. The recuperative action is so rapid that, when a telephone is put into the circuit, the note of a rapid break on the generating coil is reproduced." — Amongso the newest inventions in the sphere of war technics, says a Berlin correspondent, is an acetylene reflector designed by Lieutenant yon Kries. The fact cannot bo disregarded that acetylene will play an important part in wai. The acetylene industry ha& hitherto been busy constructing only lamps, etc.. bai Lieutenant yon Kries is the first to have lormed an acetylene reflector, and, in the opinion of Professor Goeltig, with great success. The developer of this portable reflector can also be connected with a specially constructed operation lamp 'for use in the operating and dressing tent of the ambu lance detachment. The reflector, whioh io intended especially to serve for searching for th-i wounded on the battlefield, consists of an acetylene developer borne on the soldier's back a,nd the reflector itself, which is fixed to a detachable stand made of a Mannesma-nn tube. The developer is filled with about one kilogramme of calcium carbide, and gives out a light of 50 to 60 normal candle power, lasting about eight hour.'. By means of a special arrangement of parabolic magnifiers this candle power is doubled. The reflector is made of nickel, and can be manipulated with ease, turning in all directions. By the use of this new invention the wounded can be seen, even in unfavourable circumstances, at a distance of 80 to 100 metres. — There was recently a successful trial in St. Katherine's Docks, London, of a method of rendering boats unsinkable — the invention ' of Mr B. S. Norris — a method which is as '■ simple as it is effective. Supposing that he ■ wishes to apply -the invention to a lifeboat ! which is already fitted with water-tight com--partments, he would fill those spaces with an indefinite number of closed tubes, each only a few inches long, made of some strong impervious material such as waterproof paper. But a boat with such compartments is not accessary, for the little cases can be held in a canvas band which can be nailed aloi\# the sides of any ordinary row boat, f>nd yonder it quite unsinkable. The principle oan

also be applied to lifebelts- and buoys — replacing the cork ordinarily used, with a great saving of expense. In the trials preferred to, a specially-designed boat, with canvasheld tubes along her sides as well as fore and aft, righted herself after being purposely capsized, although fitted with a mast and sail; while an ordinary boat similarly treated failed to sink, although the bung was removed to fill 'her with water, and seven men were aboard. These hopeful experiments were witnessed by representatives from the Admiralty and various shipping authorities. — According to Dr Gall, everyone is constituted so that he cannot assimilate more than «, certain quantity of sugar without the sugar remaining in the blood. Beef gives muscle, but sugar and other hydrocarbons give strength. Sugar is good to take when one has to make an effort for a long time. Alcohol is a hydrocarbon, but it depresses after elevating, and it destroys resistance to disease. Sugar does not depress, and is a food. If workmen took more sugar they could do with less beer Horses are now fed on sugar in Paris. A ration of nearly 1.22 kilogrammes a day with maize, straw, or hay is found good by a cab company of that city. Horses thus fed drink less. France, following Germany, is adopting sugar as a ration for soldiers. Workmen of all kinds, cyclists, and others ought to take more sugar. — A series of observations with a deep-sea ciurent meter, carried out in the large Strait of Bab-el-Mandeb by the officers of H.M. surveying vessel Stork, are referred to by the hydrographer in his report. The observations, which are valuable as bearing on the Bystem of circulation in the oceans, have been published in a report on the undercurrents of the Straits of Bab-el-Mandeb ; but the broad result may be briefly stated. There was a permanent current on the surface setting into the Red Sea of about one and a-half knots an hour. There was at 105 fathoms deep a permanent current of about the same velocity setting outwards. The tidal stream was about one and a-quarter knots at its maximum, and flowed for about 12 hours each way, as might be expected from the fact that in this locality there is practically only one tide in the day. This tidal stream prevails to the bottom with variations of strength. Somewhere about 75 fathoms below the surface is the dividing line between the two permanent currents, but there were not sufficient observations to determine the exact depth with any precision. — Nature. — Amongst a hundred and one other ingenious labour-saving devices, the grain elevawcttiderfully effective pneumatic variety. Here (a) it is shown in one of its most useful forms, it is shown in one of its most useful forms, the floating elevator. Laden with grain, the vessel (b) has come into port to load into barges (cc). The elevator is moored in be-

tween : and through the pipe (d) sucks up the grain from the hold of the ship and expels it again through distributing pipe (c) wherever desired. The flexible pipe can be carried down into the ship's interior, round corners, over obstacles, and so forth ; and where the grain has to be delivered into a granary, the nozzle of the outlet pipe, fixed high, up close to the roof, allows the grain to fall upon the floor, and accumulating, pack itself evenly until the entire building is filled. — A timber gill is a wonderfully well-de-signed, thoufgh a very simple, implement^ It is worked thus: First the gill, which is a kind of very high-wheeled cart, made to carry its load beneath the axle instead of above it, is run over the tree to be removed. Then the horse, which drags it by means of chains fastened to hooks -at the end of shafts, or sometimes to a pole resembling that which in Africa is called a dissel-boom, is taken off, and the shafts are thrust backwards till they stand pointed to the sky. Next the chains are made fast round the bole of the tree, and drawn up taut to the arched and ironed timber axle. Then, if the load be moderate, one, or, if heavy, two, men, with the help of the leverage afforded by the length of the shafts, drag them down, and the great tree swings up from the ground. Or should it be too weighty for their efforts, the aid of a horse is called in. Next, the load having been arranged so that it balances, the hooks are slipped through the eye. and away walks the horse, dragging after him a baulk of timber that in many cases one would have believed to be quite beyond his strength. — Longman's. —Mr Emile Berliner, a well-known American electrician, has found a way of making the gramophone, which is a variety of the phonograph, speak loudly, so that it can be heard over a large hall. He uses a number of gramophones, all made alike, and all containing the same speech or music to be delivered to the audience. They are all driven by the same motor, at the same speed, together, so that their united voice? blend, and appear as one strong voice, which can be heard distinctly in every part of the hall. —It is truly woifclerful how in these days the powerful searchlight of science will reveal the lurking places of insidious disease. By countless almost imperceptible signs the medical expert is able to detect decay where decay has fixed its stronghold. By a few marks in the finger-nails and teeth specialists in diseases of the nose and throat can note the progress of catarrh. A peculiar incertitude of gait denotes the beginning of a disease in the brain, that will inevitably end in madness and death. The wife of a well-known lawyer was troubled with an unaccountable j dimness of vision. She visited a famous oculist, who turned a light into her eyes. He found certain characters on the grey tissue which told him that she was the victim of an unsuspected and incurable disease. She had but two months more to Jive. The colour of the skin, the breathing, the shape of the fingers, the glance of the eye, all betray to the scientific observei the condition and probable duration of that strange powei within .is called life.

The Logan Berry is sold by Nimmo and Blair, and is the finest berry of its class. It is a cross between the raspberry and blackberry, and cannot be excelled for jams or jellies, having a most delicious flavour. Price, '2s 6d each, or, if postal 3s each*,