SCIENCE, MECHANICAL INVENTIONS, ETC.

New Zealand Herald, Volume XXXIX, Issue 11872, 25 January 1902, Page 6 (Supplement)

SCIENCE, MECHANICAL INVENTIONS, ETC.

' '<.. ' -• ••.v • - - * f - •r" j'-;..• :V •' .' • , - FIREMEN AND LIVE WIRES. Firemen havo • received electric shocks, in ■> playing the hose ,on buildings fitted with ; . electric wires carrying currents, or "live wires," as they are called, and experiments • on* the subject .have been made by Signor Semenza in the laboratory of the Milan i Edison Company to find the length of water jet through which an electric shock can be felt with different currents. In the trials ■ & fireman held the metal nozzle of the hose •••: .with bare hands and stood in wetted boots near the "earth" of the circuit. A current of 200 volts was not perceptible through a jet 12 millimetres in diameter until the jet was only about one inch long. A current of 3600 Volts, the highest used, gave a shock that was quite endurable for a length of one metre, and perceptible through a length of 3£ metres— is to say, about lift or 12ft. .The conclusion of tho author is that firemen are not likely to be injured by shocks unless they actually touch the wire with the nozzle. THE DIMINISHING VALUE OF PATENTS. " Engineering says that so far as patents, which are the property of the firm either by purchase or original invention are concerned, it is undoubtedly right that they should be ■ written off within the limits of their respective lives. They confer a monopoly for a limited period only, and on the expiration of that period their value as partners has disappeared. It is better that they should be stated in the- balance-sheet as a separate item from goodwill, so that they may be gradually depleted as the exclusive rights tend towards expiration. But it is possible that as the value of the patents, as legal patents, decrease the value of the goodwill of the works may increase, and the same process may occur where a patent has not been purchased, but remains the property of the original patentee, being worked by the firm , under a license. It is not a matter of legal right or exclusive privilege; the dog-in-tne-mangcr policy is wholly untenable, but the acquired skill of , the workpeople, the adaptation of machinery to the end desired, the technical ability obtained by the managers, may assure to the firm a virtual command of the market more certain and lasting than the merely legal right could give. 5 SEASONING WOOD.

A new method of seasoning wood comes from Austria. The wood is placed between two lead plates, in a wooden vat, and immersed in a solution of resin and soda. The solution is absorbed by the wood, while it is said that the sap rises to the surface. The operation lasts from five to eight hours, and then the wood can be dried quickly by artificial means. WATER-TUBE BOILERS.

Despite the many mishaps which befall them it seems certain that "water-tube," or " tubulous," boilers in an improved form ■will be the boilers of the future. With ■water-tube boilers, of which the Belleville, Thoraycroft, and Yarrow are the best- •> known types/ extraordinary care and regularity are required. . The amount of water contained in them at any one time is only a tenth of that held by the " water-tank" or "locomotive" boilers which they succeeded, but it. is difficult to impress on their custodians that, since the amount of water is diminished, its importance is correspondingly increased, and that a gauge which was formerly visited every half-hour must now be inspected every three minutes. The v general principle of the water-tube boiler is not new, but it exactly reverses that of the locomotive b'oiler, in which tho water was ■ contained in a large tank and the stacks or " elements" of tubes lie in the fire. In a h battleship the length of these tubes amounts to several hundred feet-, so it may be easily understood that they form a source of constant anxiety. They become "furred up" by the deposit of alkali if grease or salt •water leaks in, and they have a large number of joints, which cannot be kept altogether clear of the flame. Again, to develop any given pressure of steam tho same amount of water is required for either tank or tube boilers, but since in the tube boilers the quantity used at any particular time is . reduced to a' tenth the pace at which it moves must be ten times as great. If, therefore, the feed-water is checked, tubes at once become red hot, and an explosion may perhaps be the result. Still, Belleville boilers have been used in the French navy ' since 1885, and they meet with great success. This may, perhaps, be accounted for by the close attention that is devoted to jhem. Frenchmen naturally carry exactness to a degree which we should almost call "finnicky." They treat the joints of a boiler as they would the, works of a watch, and as this is precisely the treatment which water-tube boilers require excellent results are obtained. It must be remembered, how- • ever,, that whereas our ships are constantly at sea French men-o'-war are seldom out of harbour for any length of time, and their boilers have not, therefore, been subjected to severe trial on the very point on which . they have shown themselves to be weakest, for it is at such times as when steam is maintained at high pressure for a considerable time and there is no chance of mending leaky joints or clearing tubes, that water- . tube boilers give way. The locomotive boiler was easily cleaned, because a man could get inside and scrape it, but in'tube boilers the joints are innumerable, and the tubes measure from one inch to four inches in diameter, and are therefore most difficult of access. However, economy of space, rapid generation of steam, and a great reduction of weight are the undoubted quali- . ties of the newer system, so the necessity of using it in the case of torpedo destroyers • is no longer disputed.Morning Post. XI..ECTKIC LAMPS ron BUOYS.

Mr. H. J. Cloran, Mayor of Hawkesmury, : Canada, has invented a system for doing away with buoy: and lighthouses in the St. Lawrence, between Montreal and Quebec. A cable is to lie in the middle of tho navigable 'thannel and feed electric lamps on floats marking the edges of the channel. The lights are to be of different colours. USE OF THE WIRE SAW FOlt QUAJRRYIXG. Prof. C. Le Neve Foster has conferred a great benefit on the Welsh mining industry , by directing attention to a new method of ■ slate mining recently tried in the Pyrenees. At Labassere the wire saw is employed to make horizontal cuts across the inclined beds of slate, severing off great blocks without blasting. Investigation shows that slate might be worked in many quarries in North Wales by the wire saw method with conspicuous adviintages. There would be lessened -blasting, fewer falls of ground, less waste of good rock, reduced cost of working, less cost of explosives, a saving in the cost of unproductive work, a saving in the cost of removing rubbish, no need of quarrying worthless rock in underground workings, and the cost of examning and securing the roofs and pillars would be done away with. The helicoidal wire saw has been employed for quarrying marble in Belgium and in Italy for some years. It is an endless cord, composed of three hard wires twisted together, which is made to travel along by machinery and is fed continuously with apnd and water, the sharp particles of sand gradually cutting a groove. As the groove is deepened the cord must necessarily be kept . applied to the rock. This is effected by guiding-pulleys mounted in pits sunk at the ends of the proposed cut. These pulleys must be at least 20 inches in diameter, rnd the pits somewhat larger. For sinking these -pits there are employed in some Belgian quarries a rotative borer composed of a steel tueb cutting an annular groove. The wire • saw was applied at Carrara for subdividing blocks of marble, but the impracticability , of using the revolving cylinder or hand labour for sinking inclined pits was an obstacle to its further use. Tho difficulty, was, however, overcome by Mr. A. Monticolo, who invented an ingenious appliance which he termed a penetrating pulley, which . was first applied in March, 1898, at the Campanile Quarry, Carrara, where cuts have • been made 50 feet long and 16 feet deep, inclined at an angle of five degrees from the horizontal. The highly, satisfactory results ; . obtained with the penetrating pulley serve to show that there is a great saving of expense by the' substitution of bore-holes for v pits, far less waste of valuable marble, and increased-rapidity' of quarrying, and consequently increased --Nature. ' •STEEL HOOFING. A i &v system of steel roofing has been patented, which may displace galvanised ■ ; or . r ° ofing purposes. The system of manufacture consists of steel strips bent cold ! - via;™ ess -. th ? covering being formed of . sheets bent back on the " edges and locked into tubular rafters.