SCIENCE, MECHANICAL INVENTIONS, ETC.

New Zealand Herald, Volume XXXVI, Issue 11200, 21 October 1899, Page 4 (Supplement)

SCIENCE, MECHANICAL INVENTIONS, ETC.

TO PROTECT WOOD AGAINST THE CONSTANT ACTION OF MOISTURE. Wooden vessels containing continually aqueous liquids, as well as wooden shafts and other parts of machinery constantly ex- | posed to dampness, will suffer in time if no protective coating is put on, a decomposition of the surface, which advances gradually to the interior and must finally destroy the article. In the Zeitschrift fur Landwirthschaftliche Gewerbe, various receipts for protective coverings on wooden objects are given. For enameling vats, etc., 1 kilo. I of brown shellac and 125 grammes of colo- j phony are melted in a spacious kettle. After the mass has cooled somewhat, but is still thinly liquid, 6.1 of alcohol (90 per cent.) is gradually added. In order to prevent the ignition of the spirit vapour, the admixture of spirit is made at a distance from the stove. By this addition the shellac swells up into a semi-liquid muss, and a larger amount of enamel is obtained than by dissolving it cold. The enamel may be used for wood or iron. The wood must be well dried; only then the enamel will penetrate into the pores. Two or three coats suffice to close up the pores of the wood thoroughly and to render the surface smooth and glossy. Each coating will harden perfectly in several hours, The covering endures a 'heat of 60 deg. to 70deg, C., without injury. This] glaze can also be mixed with earth colours. 1 Drying quickly and being tasteless, its applications are manifold. Mixed with ochre, for instance, it gives an elegant and durable floor varnish, which may safely be washed off with weak soda solution. If it is not essential that the objects be provided with a smooth and glossy coating, only a preservation being aimed at, the following coat is recommended by the same source: Thin, soluble glass (water glass) as it is found in commerce, with about 24 per cent, of water, and paint the dry vessel rather hot with this solution. When this has been absorbed, repeat the application, allow to dry, and coat with a solution of about one part of sodium bicarbonate in eight parts of water. In this coating silicic acid is separated by the carbonic acid of bicarbonate; from the water glass (sodium silicate) absorbed by the pores of the wood, which, as it were, silicifics the wooden surfaces, rendering them resistive against the penetration of liquids. The advantages claimed for both processes are increased durability and facilitated cleaning. STRENGTH OF ALUMINUM. Metal workers frequently ask: " Wlui* is •the strength of aluminum?" The t'.nsile, crushing and transverse strength of al'.minum varies considerably with different renditions and hardness due to cold working, also to the amount of work that has been put upon the metal and character of the s'Ction, and the amount of hardening ingredients. Cast aluminum is about equal in strength to cast iron in tension, while under cvgrthmhuk( mpression ife is comparatively weak. Taking the metal 99 per cent, pure, the ultimate tensile strength per square inch in castings i i 18,0001b ; in sheet, 24,0001b to 10.0001b; wire, 30,0001b 55,0001b; and bars, 28,000 bto 40.0001b. As compared with copper, the average tensile strength of which per uare inch is authoritatively stated to be as follows: —Cast, 19,0001b; sheet. 30,0001b; bolts, 36,0001b; and wire, 16,5001b. Pure .iluminum compares with copper in the sar e manner that alloyed aluminum 'compares with brass. The elastic limit of 99 per cent, pure aluminum is for. castings m tension, 85001b; sheet, 12,5001b to 25,0001b; wire, 16.0001b to 33,0001b; bars, 14,0001b to 23,0001b per square inch. Under transverse tests aluminum is not very rigid, although the metal will bend nearly double before breaking; while cast iron, under similar conditions, is broken very easily. The tensile strength of aluminum is greatly improved by subjecting the ingots to forging and pressing at a temperature of 600deg. Fab. Taking the tensilo strength of pure aluminum, in relation to its weight, it is as strong as steel of 80,0001b per square inch. Aluminum, properly alloyed with nickel, is much stronger than the pure metal, as may be seen by the I following figures: Nickel aluminum has an ! ultimate strength per square inch in tension in the form of castings, of 18,00011) to 38.000 lb; in the form of slicet. of 35.000 to 50,0001b; and in bars, 30,0001b to 45,0001b, The elastic limit in tension per square inch of nickel aluminum is as follows:—In castings. 85001b to 12.0001b ; sheet, 21,0001b to 30,0001b; and bars, 18,5001b to 25,00011). The average tensile strength of brass, when cast, is 18,0001b per square inch; when in the form of wire, 49,0001b. Bronze or gun metal has an average tensile strength of 36,0001b per square inch.—Aluminum World.

TRANSPORTING POWER OF TITE WIND. There are few people, aside from geologists, who realise the transporting power of the wind in the geological sense. This ability of the wind to shape the topography of the earth's surface is known as /Eolian .erosion. In many places it lias manifested itself by piling up mountains of sand in great dunes, and in other places the drifting sand has scoured the rocks into fantastic shapes and polished their exposed surfaces like an artificial sand blast. At the mouth of the San Gorgonio canyon, on the line of the Southern Pacific Railway, in Riverside County, Cal., not far from Whitewater Station, tho rocks on the west side of the road are carvcd in deep nits and polished by the sand and gravel driven before fierce blasts of wind, which rush down through the narrow pass between the San Bernardino and San Jacinto mountains on to the Colorado Desert, to fill the space made by the rapidly rising air which ascends from that heated land. Near Palm Station, where the wind loses much of its force, the sand is piled up in great dunes, some of which rise 200 ft or 300 ft above the desert plane. Still farther down toward Pilot Knob, near the Moxican boundary, the winds which rush across the Salton basin have piled up miles of sand dunes. These are ever shifting, always changing. On almost any clear day scores of whirling columns of sand, mounting often over 1000 ft into the air'and visible for miles, may be seen over the vast expanse of this desert. These instances are only mentioned as characteristic of many other places on the Colorado and Mojave deserts of California, and in hot, dry, sandy .countries everywhere. Along the sea coasts and lake shores, where not rocky, sand dunes are of very common occurrence. A large portion of the city of San Francisco, Cal., is built on sand dunes, formed by the drifting of sand from the shores of the Pacific, driven by a prevailing south-westerly wind. In places these piles are 100 ft or more in thickness. In some places growing forests have been enveloped by drifting sand, and in after years the sand blown away again exposes the dead forests.—Mining and Scientific Press, THE EFFECTS OF AMMONIA. Be cautious (says Science Sittings) with ammonia. Recently an unfortunate woman named Parker, of West Bromwich, England, smashed a bottle of ammonia whilst washing up some crockervware. She inhaled the fumes, and gasped for her breath. On recovering a little she stated that as soon as she pulled out the cork the ammonia flew up into her face, causing her to drop the bottle. Dr. Manley said at the inquest that i in the great heat that prevailed the ammonia would have a greater effect than ordinarily. The taking in of the fumes was > quite sufficient to cause inflammation of the : njouth, and death, which intervened, was ! due to suffocation of the throat. i AUTOMATIC STEERING RECORD. ; An apparatus has, says an exchange, been , devised by means of which a record is auto- , matically taken of the extent to which the steering wheel of a vessel is moved, and the • helm is shifted. The use of the apparatus is [ a couple of drums on which a "tape" or . long strip of paper is wound. The move- , | ment of- the helm naturally detracts from , ! winding the tape from one and winding it [ j on the other, the motions being obtained i | bv suitable toothed gearing. In the same : way a pencil fixed to a holder is caused • to move to one side of the central line of , the paper if the helm is put to port, and > the other side when the helm is starboarded, . the amplitude of the movement of the pencil . j being proportionate to the angle of the helm, i j In this way an accurate record may be kept ' of the number of times and the amount the , helm is shifted. The use of the apparatus is ; to afford evidence of the helm movements in cases of collision or stranding, Another use suggested for this recorder is to show the skill of the helmsman.' It is well known that [ some men will keep a vessel on her course with far less helm movement than others. he yawing of a ship due to excessive mover : ment of the helm naturally detracts from ■ speed, and causes more coal;to be burnt than 1 would otherwise be the case* ■ •r V . \ . - •A