SCIENCE MOTIFS

Otago Witness, Issue 2292, 3 February 1898, Page 46

SCIENCE MOTIFS

• . • A proposal has been made by M. Gabriel Viand, a French chemist, to obtain easily assimilable iron tonics from vegetables byfeedirgthe plants judiciously with iron manures.. It would be interesting •to know whether a suitable amount of iron could be absorbed in this manner.

• . ■ Some scientists thick that the earth's interior is composed of white-hot rnolien matter. O here are of opinion that the pressure is bo great that all substances have been condensed beyond our powers of conception. Df Ycang goes so far as to sa.y that a block of steel lOffi square would be pressed into a block only 2?t tqaare if taken 4000 miles balow the eaith's surfac?.

■ . • Henry Ehodep, of Denver (U.S.A ), has a patent for "an improvement in the process oE separating gold and silver or other precious metals from tha ores." The preparatory method is to grind the gold and silver ores to the desired fineness and then add a certain percentage of common gypsum, also reduced to a certain mesh. To the ground oieß and gypsum is added water, and the thorough mixing or churning of the primal ingredients begins. When the m!Xirg or churning reduces fcbe ore and gypsum to a consistency of clay the matter is taken out and moulded into auy form desirable, and is left to dry, which takes but a very ghort time. After the biicks or slabs have dried they are ready to be dumped into tarks or other receptacles, and the cbemical solution is turned on. The matrices being entirely poroue, tha chemicals permeate tha bricks and, the patentee cairns, carry away in solution from 95 to 99£ per cent, of all gold in the ore.

• . ■ At the London Institution Professor Silvanus P. Thompson gave a lec'ure on signalling across space without the use of intermediate conducting wires. After giving a short account of the references found in mediteval wiitera to sympathetic telegraphy by means of the magnetic needle, the lecturer described seveial methods of sending signals by electricity between distant places without intervening wires. The first was by conduction. If, for instance, two pairs of metal plates were placed in the water of a river, one pair being on each side, with its two plates connected by a wire along the bank, then the water could be used to complete the ciicuit, provided the plates wera at a proper distance from each other. The second method was by induction, and bad been used on a practical gcal-i by Mr Preece, The third was by means of Plert zian waves. Hertz proved experimentally that when electric sparks wcra made electric waves were given off in every direction, and he showed how these might be detected. Lodge in hiß coherer found a simpler and more satisfactory way of detecting them, but the idea of using them for telegraphing to long distances was apparently not contemplated by him. Tesla, in 1893, was the first to appreciate this possibility, bub press of other work prevented him from carrying it into practice. More recently the British Post Office had taken the matter up at the instigation of a young Italian— Mr Marconi. The lecturer had not been able to find out was new in the apparatus of Marconi,

who had simply improved the coherer. However, he had been able to signal for a distance of three miles on Salisbury Plain, and about nine near Cardiff ; while in Germany recently, by using a sufficiently high base lice, it had been found possible to detect the waves with a coherer lika Lodge's at a distance of 13 miles.

• . ■ In tb.B utilisation of water power America leads the world with a total installntioa of 70,000-h.p. Swiizarland comes next with 32,000-b.p. Fracca has 18,000 h.p , and the great plant at Rheinfelden v?ill give Germany the fourth place with about 17,000-b.p. I'aly has nearly a3 much, and Norway and Sweden are each credited with 15,000 h.p. Great Britain is far behind with a total installation of about 4000-h p.

• . • Sodium is made by the Castner procass of decomposing sodium hydroxide ekclrolytically at Birmingham, Eegiand, at the rate of about 20001b per diem, the product being worth about 50c per lb. The process has been introduced at two or three places in Gernipny, and in the Uaited Spates at Niagara Falls. Tha cost of making fcodium by this process is regret ; very little of the metal is sold, the most part of it being con-f-umed by' the producers for the manufacture of sodium peroxide. It is said also that a good dt=al is used in tha manufsc^nre of potassium-sodium cyanide, it having been proved that wbea the yeilow prussiate of potash is heated with sodium neither oxygen nor alkaline carbonates are introduced, the product being an almost chemically pure mixture of sodium aaci potassium cyaoides. • . • Dr J G. M'K--ndrick, of Glasgow, is just now atiiactis g great attention in the Fcieniilic wosld with bis experiments on a prccfss of c ■mranmcatiog ths charms of music t-o deaf poopls. By means of an iogemous contrivance he has succeeded in communicating to electr'fvrd wafer vibrations of sound which corre«r.ond exactly to the various rhythms. A deaf person by keeping hia hands in this water cm iuUy er j >y the music.

■ . • A new met preventer is highly spoken of by engineers, who claim that it has at length overcome one of tha greatest sources cf trouble with which those who have cbarpe of machinery have daily to contend. It has been adopUd by the German army and navy, and by a large cumber of European tnanulaciurers. ]>. is composed of greases and volatile oils, wh f ch evaporate on espc-sure to the air, leaving sn air-tisjht film or !-kir, v.hich adheres tightly to the mett.l and absolu'tly and prevents the corrosive sction of salt air, sflt water, rair, snow, dampness, steam, ga?es, and fumes of acid or arnraonia. It is neither a paint nor lacqner, nor a product ot petroleum. It is, i\ti<l remains, absolutely neutral, con<a ; ns bo acid, and leaves neither spots nor mark a when removed. The coating is transparent, and ss it doe>3 aot dull the p.ppearanca of bright m&Sal surfaces', it is of tpecial service to machinery builders and dea'ers who have goods ie stock. It does not ci&ek and is not aborted by dust, paper or cloth wrappers, nor does it rub off in handling ss do oils and petroleum jel'ie?. This quality ra-.kes il invaluable for the Bhipoers of csaciunery. As it stands a very high tetrp~3ra(ure without meifir g, it can be used on the bright parts of boil-re, engine**, &<\ A given quantity covers a 'nrge amount, ot rurfacp, one gallon being sufneent to protect" 1100 squira fret. Ir, is easily sppljtd wi~h a rag or soft bruth, and can as quickly be removed with uxrpentieeor benzitie, a point of superiority over white tead. Ifc is claimed that an srt,ic!e occa coated with it is protected from rust as long as the film is allowed to remain.

■.• M-tny of the failures of cast-sieel apparatus are duo to fUw=. The drooping of big guns, the bursting of smi-iller orts, the fracture of- engine crank*, railway whe' Is, and propeller shafes are more often due to hidden fkws in the steel than to any other ca.use. This hss made it a matter of momsnt tbafr. some plaa by which the occlusion of air could be absolutely prevented. A new invention designed for this purpose has been patented by W. E. May. By this process the castings are made in an air-light chamber from which the air is exhausted, the mould or casting being placed in the chamber before the exhaimion ot the air. This chamber is surrounded by a series cf other chamb&rs, esc'n connected with the central chamber by a pipe con trolled by valves. In these chambers a reserve of vacunm is stored, the air from them being exhausted by vacuum pump 3. When a castirg is ready to be run iii the controlling valven are opened aod the residua of air in the casting chamber i; 4 inptantaneously sucked out into the su/roundirg chambers at the same moment that the molten steel is pcurad into the mould. Ths casting thus takes place in vacuo, the secluded air and gases rush out of the fluid metal and diffuse themselves in the vacuum chambers, and a flawkss, homogeneous steel casting is the result. In Ihe case of large ingots or armour plates the process provides additionally for subjecting the fluid metal to uniform compression by means of hydraulic power while in vacuo, so that cavities which might result from contraction of the metal while cooling will be rendered impossible. It is usual at present when making large castißga to use about 4.0 per cent, more metal than is required for the work, because the ripper psrt of the ingot, being permeated with air and gas bubbles, has to be cub eff and discarded as useless. By the May process it is claimed that this waste will be avoided. There seems to be some diversity of opinion as to the practical value of this -method of casting eteel ; and the process is not receiving much encouragement from steel manufacturers. This, however, was the case with the Harvey process till its merits were demonstrated, • . ■ Aa invention which people in this country will not take up is the automatic writing telegraph. You write at one end of the system, and at the other end a pen writes out what you have written in your handwriting. Sketches can be transmitted in this way even at a distance of 200 miles. There is 50 tirnss as much invention in the apparatus aa there is in the telephone, but apparently no one wants it.

' , • The estimate is made by Prof. William Hallock, who has now in charge, for scienti fi purposes, the deep well near Pittsburg, Pa., which, when completed, will be the deepest known, reaching two mile 3 down into the earth, that the ultimate result of the boring will be of decided geologic and economic interest. One remarkable feature of this well is that the gas found near the sur-

face is now nse'd to'opsrate the engines which do tha drilling. According to Prof. Hallock's estimate, the tsmporature of the we 1 ! at 10,000 ft, its proposed depth, will be 228deg, and, as at 212 3eg water is converted into vapour, he expresses the opinion that the well will aSor'd an ample supply of natural steam that will prove to be the cheapest power available to man. It is generally believed by scientific men that the temperature of tha earth increases ldeg for every 60ffc of depth, but this general rule is subject to exception?, and in this case very material onep, because tho increase of temperature is said to be not uniform. Thus it is known the crust of tha earth i 3 esposed to quite as various conditions aa it 3 surface. Granite, for instance, especially if it carries much feldspar, gives off more heat than slate or other rock containing a high percentage of hornblende ; lime give? off still more heat, at any time and in a'nrvt any condition, bub especially when " sh'v.kod " or decomposed by sudden contact wit h air or water — or both. These varying conditions, which cause widely diverging effects, are what constitute the element of uncertainty in such calculations as the above.— Sun.