MODERN SCIENCE.

New Zealand Herald, Volume LXI, Issue 18843, 18 October 1924, Page 7 (Supplement)

MODERN SCIENCE.

Hp ITEMS OF INTEREST. . ADVANCE IN ASTRONOMY. > II remarkable instrument. - J - 'An instrument that is expected to have a great influence on the teaching of popular astronomy has been installed at the Ifiy . Germw Museum of Natural Science and I Technology in Munich. It is the product $ 'ot the optical firm of Zeiss, and has been ' nndor construction for five years. The chief advantage of the machine lies in tho . fact that it substitutes a realistic and accurate picture of the happenings in the heavens for a confusing arrangement of wires and wooden balls heretofore used. The " planetarium." as tho instrument Is called, is of unusual, even weird and startling appearance. There is something about lis general make-up that would suggest a small anti-aircraft cannon, but instead of ending in a long barrel it has M its most essential part a largo sphere gtudtl''d with high-power lenses, resembling a gigantic insect's eye. Each of these lenses is arranged to project the imago of a certain part of the heavens, so that the whole starry universe can be made* to march across the dome-shaped coiling of tho "sky room," where the planetarium is housed. All stars down to the sixth magnitude »re shown, as well as the milky way, the planets, the sun and the moon. The ingtrurnent can be rotated at any speed, ihowing the celestial ovents of a day in period of four minutes, or crowding a year into fifty seconds. Within the artificial sky of the planetarium study the operator has the power of a Joshua; for he can bid the sun and j jno;-n to stand still, and cause the stars ft' to run "backward in their courses. So 9 accurate is the instrument that after P rotations, representing five thousand years, there is an error of less than two degree®. ELECTRICAL DISCOVERY. The discovery has been made by Professor Geiger, of Michigan _ University, that crystals of silver _ sulphide generate electricity under the influence of light. Thb amount of electricity produced by light Is very small, but the discovery may have important results. i | WONDERS OF THE M3OROSCOP3. Microscopic analysis of cross-sections of fragments of a fossil tern have revealed the living anatomy of giant plants which flourished aeons ago, Professor W. T. Gordon, of King's College, London, announced to the British Association for the Advancement of Science at Toronto. Petrified stems the size of trees, twigs clothed with bark, and buds with their leaves attached recently found in Haddingtonshire, Scotland, show that this fern was much simpler than formerly supposed by botanists. HEW METAL INVJEUTIOH. I An American motor manufacturer ha« ! invented a new metal for use in places where there is excessive friction- It is a copper-tin bronze in which graphite has . been incorporated, and tho remarkable thing about It is that ft will absorb oil like blotting paper. Thousands of email pores honeycomb the metal, and these absorb lubricant np to as much as 25 cent, Sf the total mass of the piece. The oil / oes not drain out, but works to the sur- ' face gradually, and this obviously gives 1 ideal lubrication. The metal is said to be hard enough for the roughest bearing ! wear. I ——— V i COLOURS OH THE MOON.

t I Bom® remarkable snapshots of the moon ' \ fcive been shown at a meeting of the Bril tish Astronomical Association by Mr. F. ' \3. iUrgresvas, who has elaborated a new ' *»* of photographing the moon in colour I tlu»ngh the refracting telescope of the I HW&y Observatory. These natural colour photographs show that the general tint of i tha moon's surface is lifts that of dried : mnd, or the weathered Portland stona of I London churches. But in some of those ; largo darker patches on the moon, which j have been long but wrongly called seas, j the colouring is brighter. The Sea of j Tranquillity is olive green ; the Be* of ' Serenity is brownish i and the £.w» of Imi bHum 11 mottled brown and olive green. ! There is one other sea, that of Aristarchna, ; which from its* yellowish tings is believed ; to have deposits of sulphur. . UmSTBLE HANDW2ITIII. ' The simplest means ever employed in secret-letter writing was to .write the messages with fresh milk instead of ink. On the receipt of a blank sheet of paper, ail the recipient needed to do was to 1 sprinkle it with soot or charcoal . The ! pit stuck to the lines traced by the pen. When the trick was of no avail, chemists i would perform the task of writing with . acetic acid. Another chemist spoiled ! sulphuretted hydrogen gas to the letter i •ad the secret was unfolded. Another | " sympathetic" ink is that prod seed from cobalt, the writing of which disappears in | the cold, but appears again as often as I one chooses after being exposed to a | moderate decree of heat. Characters written in diluted sulphuric »cW and lemon-juice become black or brown; i those written in solutions of nitrate and i chloride of cobalt and of chloride of copper { are rendered green, the colour disappearj ing when the paper is allowed to cool in a ; moist place. | MAKE CHOPS SOIL. ' A suggestion that is expected to have try much significance in the scientific developP toent of diversified farming is put forth by s* , Dr. E. T. Wherry, of the Bureau of Chemistry of the American Department of . Agriculture. It is that the farmer, instead of trying to force his soil to produce the kind of crop he t links he must raise, by the heavy and expensive application of certain kinds of fertiliser, should study his Boil and find what kind of crop it will frow mcst economically under natural conditions. Forcing a soil to change its chemical nature by liming or other fertiliser operations to make it fit a conventional crop, it is urged, is poor business when some other kind of crop may be grown on it at a profit as it stands. There sre beginning to be available considerable masses of scientific data indicating the preferences of various kinds of plants as j to the chemical conditions in the soils in | which they grow best, and there already j exist several practical and rapid methods j ci getting soil reactions.

the HEART op a DIAMOHD. What is the difference between an engagement ring and a lead pencil ? In other words what is the difference ' between diamond and graphite? Both are pure carbon. Professor W. L. Bragg, recently awarded the Nobel Prize in pwysics, explained the points of divergence in a lecture at the convention of the British Association for the Advancement of Science at Toronto recently. "In the diamond," he said, " each atom of carbon « surrounded by four similar atoms grouped symmetrically around it, and all &"> the same distance away, namely, one-•nd-a-half hundred-millionths of a centimeter, a distance which the X-ray enables W9 to measure to one part in a thousand. ■^ <5^ re struck by the remarkable grouping of the atoms into rings of six. In graphite ♦ j o ' the neighbours of the carbon atom draw even a little closer to it than diamond, but the fourth moves away. The crystal is, In fact, in layers. £ach atom in a layer has three neighbours arranged symmetrically around it. ** ut 11 i* a ' on way rom one layer to the next.. The layers have 80 little hold on a ach other that they slide over one another very easily, but each layer is very tough in itself. It is the combination of these properties that makes graphite so perfect a lubricator although diamond, the crystal, will scratch any-

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