SCIENCE, MECHANICAL INVENTIONS, ETC.

New Zealand Herald, Volume XLIII, Issue 13325, 3 November 1906, Page 4 (Supplement)

SCIENCE, MECHANICAL INVENTIONS, ETC.

' 25,000-TON WARSHIPS. M. Latjbkut, chief engineer of the French navy, has an article in the Ma.tin declaring that the size and power of a country's battleships are the test of its naval strength. France .should, he ; says, build vessels more powerful than the Dreadnought, and she had better have four large battleships, at a cost of £2,600,000 each, rather than six at £2,000,000 each. Great Britain, he continues, leads the navies of the world because she was the first to build battleships of 15,000 and 18,000 tons, and the nation which first constructs vessels of 25,000 tons will at once pass all "competitors?. • ■•■■•• SPARROW CAUGHT IN A SPIDER'S WEB. A curious story of a sparrow's capture by* a. spider is told by Mr. B. G. Tours, of the British Consulate at Chinkiang, China. Writing to the Spectator he says: —" I sawsi full-grown sparrow caught hard and fast in a spider' web, which was built across a brick arch through which the bird was flying. The bird was caught head downwards, and his struggles only wived to entangle him the more. After a minute or so the bird appeared exhausted and gave up his struggles, I then released him, looking,, and evidently being, very uncomfortable in his extra clothes of cobweb. The spider —an elephantine beastevinced no desire either to attack or release the bird ; but he would doubtless have waited till the sparrow was dead before taking any steps." GLASS-HOUSE; CONSTRUCTION. The demand for hollow bricks and building blocks for house construction has induced glass manufacturers to put hollowglass bricks on the market, and they promise to be used extensively for novel and artistic effects. The first glass bricks proved a failure on account of their cost, but the hollow glass bricks can be made at much less expense. They are lighter and stronger than clay bricks, and are such excellent non-conductors that walls built of them are proof against dampness, sound, heat, and cold. The bricks are sealed hermetically when hot, and are placed in walls with a'colourless mortar made of special glass'. The bonding strength of the glass mortar is almost as great as the bricks themselves. For ornamental friezes, dadoes, string courses, and facades they are of special value, and add greatly to the artistic effects. For those who might- object to living in. glass houses through whose walls anyone could see, it should be said that, the'hollow-glass bricks are made both translucent' and opaque: ';' Furthermore, . the old adage that those who live in glass houses should refrain, from throwing stones lias no application to the modern glass brick house, for the bricks are made so strong than an ordinary stone thrown 'against a wall of them would rebound without cracking any of the masonry.

'SPIDER' THREADS. The cultivation of certain species of spiders solely for the 1 fine threads which they weave for scientific uses has an important bearing upon astronomy, the oldest .physical science.', No substitute for the spider's thread has yet been found for bisecting the screw of the micrometer used for determining the positions and motions of the stars. Not only because of the remarkable fineness of the threads' are they valuable, but because of their great durable qualities. Recently the set of spider lines in the micrometer of the transit instrument at the Allegheny observatory were examined and found.to be in perfect condition, although they were placed there about forty-seven years ago. The threads of certain spiders raised for astronomical purposes withstand changes in temperatures so that often in measuring sun spots they are uninjured when the neat is so great that the lenses of the micrometer eye-piece is cracked. These ispider lines are only one-fifth to one-seventh of a thousandth of an inch in diameter, compared to which the threads of the silkworm are large and clumsy. Each line is made up' of several thousands of microscopic streams •of fluid. Under the most powerful magnifying glass they appear true and round. The work of • placing these lines in the micrometer requires the delicate work of experts, who operate with the aid of miscroscopes which magnify the lines a thousand ■ times. The fines are placed parallel with each other, and ,two one-thousandths of an inch apart.

ARTIFICIAL EGGS. : The artificial egg as a commercial product having been abandoned by scientists as an impossible invention, attention is being drawn to the preservation of leal eggs for indefinite periods. Canned eggs, limed eggs, cold-storage eggs, and eggs preserved in water-glass, and other chemical compounds are now regular market products ; but the most recent egg freak consists of hard-boiled eggs preserved in clay and charcoal paste. The idea of thus utilising' the eggs during seasons of plenty is derived from China. The Chinese have preserved boiled eggs in clay for a long time, and some of them are said"to be centuries old. The eggs are boiled hard and wrapped in soft, day while hot. - The clay hardens, . and looks like pumice-stone. They are packed in bags and rice husks, and kept indefinitely. When opened the yolks are green, and' the white part almost black ; but they retain a distinct egg flavour, and when chopped fine they flavour sauces and gravies as well as fresh-boiled eggs. The duck eggs are boiled and packed in a paste of chatcoal, .which hardens about then and forms a perfect protection. Experiments are now •being matte in the egg districts of England to imitate the Chinese and go them one better. If the colour of the eggs can be j retained restaurants may in time be able to serve hard-boiled eggs" to customers with- ! out the latter detecting their great age. The character of the clay and charcoal is said to determine the darkening of the inside, a dark, heavy clay preserving the delicate white and yellow of the eggs better than the light clays. WHEEL CARRIES ITS OWN TRACK. The enormous' reduction of tractive effort produced by the use of roils has suggested to Dr. Vv. ' Houssay a wheel which carriesits own track. As described by him in the Scientific American, the main feature of the portable track is a, series of rectangular wooden - blocks, with their lower edges rounded and their lower faces shod with sheet iron. In the upper face is a shallow transverse groove, into which a short segment of iron rail is fitted and fastened to the block with two rivets. The length of the rail is equal to the width of the block, but it is placed uiisymmetrically, so that i on© quarter of its length projects beyond one side of the block. Therefore, if several blocks are laid on the ground, side by side and in contact, with their .protruding rails pointing in the same direction, each of these projections will fall in the groove of the next block, and the rail segments will also touch each other, forming a continuous rail. Consecutive segments of rail are then fastened together by short iron bars, which enter mortices in the ends of the segments, and are secured by pins?, which pass through holes in the ends of the bare and the sides of the mortices. When all the rail segments and their attached wooden blocks have been assembled in this way the result is an endless chain or band, somewhat longer than the circumference of the wheel to which it is'to lie applied. The face of the wheel has a groove lined with iron, which the rail enters and which constitutes the bearing surface. As the jointed rail is longer than the circumference of the wheel, the segments in front of the lower part of the wheel, when the latter is in motion, become separated from it, and are gently deposited on the ground, forming a smooth and straight or nearly straight track, at least two segments- long. upon which the wheel can run with all the advantage that would be afforded by a rail of indefinite length. "The hardness and smoothness of the jointed rail diminish the tractive effort, and the wide wooden blocks prevent the sinking of the rail in loose ' soil, and practically efface the inequalities of the ground by forming an inclined plane before every obstacle and depression.. A portable rail of this construction is applicable everywhere except in very wet ground , and road's badly washed ,by floods."