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Otago Witness, Issue 2317, 28 July 1898, Page 54

SCIENCE NOTES.

— While lightning may be seen and its illumination o> . !-"!iid» and mist may be recognised when it is even 200 miles distant, thunder is rarely audible more than ten miles. The thunder from very distant storms, therefore, seldom reaches the car. says Industries and Iron. Tho reason of the great uncertainty in the audibility of thunder is not difficult to understand It depends not merely od the initial intensity of the crash, but quite &9 much on the surroundings of tho observer, oveo a? in the quiet country one tnJJ obserre leeble pounds that escape the ear in a uoi?y city. Perhaps tho most curious and important condition of audibility is that the thunder wave of sound shall not be refracted or reflected by the layers of warm and cold air between the observer and the lightning or by the layers of wind, swift above and slow below, so as to entirely pass over or around the observer. Sound, in its wave-like progress obliquely through lasers

of air of different densities, is subject to refraction, and this refraction may occur at any time and place. Thus, observers at the topmast of a ship frequently hear fog whistles that are inaudible at s«a level ; those on hilltops hear thunder that cannot be heard in the valley ; those in front of an obstacle hear sounds inaudible to those behind it. The rollng of thunder, like that of a distant cannonade, may be largely due to special reflections md refractions of sound. Again, the greater yolocity of tke air at considerable altituda K.bove tho ground distorts the sound w&7« and shortens the limit of audibility to the l«eav.id, wliilti increasing it to the windward

—It is much to be regretted that Sir William Crookcs li-»JS thought it advisable to discontinue lii s experiments in regard to Dr Emxaens's production of what he has termed srgeataurum. but which he sells as gold, and claims to Jis,ve produced from silver containir.* only a trace of gold. It wil) be remembered that tho direction or particulars oi conducting the experiment given by Dr Enxixiens in his pamphlet " Arcana Nature " vrere distinctly sta(«J to relate L<» other ni4\y.!» of obtaining the. transfoimation or transmutation than those actually used by Dr AOramens himself. They woro distinctly given d? relating to a commercially unprofitable mot bod. "bat. on the otliej hand, it was alao laid down that,, if tho direct ions and instructions were, follow erf oui. correctly, silver containing a sraai. tctco of gold would at the conclvsiou of tho ejpsriraeDt be found to coataiD a greater amount. This Sir William Crooked h*a za some m?.isare conf/rmed, for }/? f era cd that 02a capsnrseat Avith silver containing a trace* of gold rep-ultcd in aa increase of nearly 21 per cent, ia tlio proportion of tfoW present. Sir W. Crooke* appears to regard this gain as witbni Iho limits of possible c«or m tho e-xpai'iwent ; but swaifagly 13? Emi'nea* tstcs a different view, and is disposed to regard it as a. proof of his contention that, gold can bs> produced fromjsilvar. A subsequent experiment, of Sir William's Aviti pure silver from Mexican dollars resulted in failure to produce airy gold ; butDr Stamens always employs Mexican dollars having a trace of gold ; this experiment is inconclusive, therefore, because, for one thing, as chemists aro aware, the presence of an element, has often an important, effect en aa experiment,. If Dr Emmens's contentions are correct, this discovery lanks in importance quite equal to any other scientific discovery of tlie age ; for his discovery not ©sly posftft-tscs interest from the monetary or profitable point of view of tho possibility of transmuting silver into gold, but it posses.se? far "wider signifiravsre in the possibly eiHire change of present knowledge in all that pertains to metallurgy and ether fields — Industries aacl Iron.

— What Surgooß-jnajor General Hamilton says abonfc explosive bnllels in impoitant, as {showing how very greatly their effects exceeded tlto*e produced by modern projectiles, ev«a wliea their eonslructioxi is modified, as in the duiv.-dam bullet, and ws cannot faiJ at once to tee lucyr desiralslo it was that their use in warfare should be prohibited as it was by tho Gtaeva Convention. As u« well known, the old Snider, which was a large expanding bullet, was a most deadly missile. It had a hollow in front Trkich was filled by a plug of wood or clay, while the base was olso hollowed and plucn-ed. On impact it became completely expanded and deformed, causing most terrible injuries t-o soft parts as well as te bosies. The next step was to leave out the plug in front, forming a hollow space there, over which the le?A was drawn, so that there was a closed cavity filled with air. On impact this air was strongly compressed, and tore the bullet, open, much wa a, small charge of jJowder wuiild have done. The

" smashing " power of this bullet was so great that it was adopted for sporting purposes 1 . "On soft-bodied animals, such as tigers and panthers, its effects were wonderful, the biggest tiger often dropping dead to a single shot wiien well placed." The true explosive bullet, however, against which the Geneva Convention legislated, was a still more terrible projectile, and when fairly struck with it no soft-bodied animal could do further mischief. The bullet was cast in two parts. The base was* hollow, and was nearly filled with ordinary powder, then a | piece of thin cloth was laid over the top and the apex was fitted in, and the two were closed together in a machine. Through the front portion of the conical bullet so formed there was a hollow, leading from the apex to the cloth over the powder. Into this hollow detonating powder was poured, the hole was closed with wax, and the affair was complete. On impact the detonating powder went off, but tke gunpowder iras svfiioiently slow in expioumg to a^ow the bullet to penetrate before it broke up. This was a typical form of expks,ive bullet, and most deadly in its effects. " I &hot a Teat deal of heavy game with Hi in India," says Surgeon-major General Hamilton, " and never lost an animal I knew I had struck. I have seen a stag 15 hands high hit behind the shoulder collapse on the spot, as if its legs had turned into jelly. On one occasion I saved my life by killing a charging bear in dense jungle, droppine hej' within a few feet of me. In this case I observed smoke issuing not only from the wound, but also from the mouth and \ nostrils, and on opening the chest found the i hear* and lungs torn to pieces." Let. us be thankful for the Geneva Convention, which prohibited the use of such missiles against man. — The Hospital.

— Fireproof wood is to be used in the construction of every future American warship where wood is needed. To make it fireproof the timber i.* placed in a cylinder and a vacuum is formed. Steam is then admitted, which causes the moisture in the wood to vaporise, and the products of the vapour are drawn off. A vacuum is again formed and the saturating liquid, containing certain salts, is forced into the cylinder until the wood is thoroughly impregnated. The -.rood is then dried and is ready for use. Experiment has proved that timber so treated is incapable of supporting or conveying flames

—At Stassfurt sodium sulphate has for many years been manufactured from the sulphate of magnesia, contained in kieserit and others of the Abraumsalze, so named becauso they used to be cleared away as useless in days gone by, and from the rock salt abounding there. If a mixture of these (wo salts in the proportion of 2 to 1 ia cooled down to

sdog Cent, and lower, sulphate of sodium crystallises out. In tho Caspian Sea nature lias been carrying on tins process, and we may expect to see soda works rise there, which may revolutionise the soda industry of the Russian empire. Nearly opposite Baku, on the eastern shore of the Caspian, is the Bay 01 Kara Bugas, a vast basin notmuch smaller than Wales, communicating with tlie Caspian by a nairow channel only. The evaporation in this bay, whose depth nowhere exceeds 50fb, is so rapid that there is a constant, inrush of water from the Cnspian. The wator of the Caspian is already salt ; it contains 0 780 grammes of NaCl. 0 £04 of MgSCH 0.081 of Ca»SO4. besides minor quantities of chlorides* and carbonates per litre Tlie high percentage of magnesia is very striking. Tho water of the bay is much more and the conditions are such that the formation of sodium sulphate ought io take place, in which case the glauber salt ought to collect on the bottom A committee was appointed to investigate the question, and we see from Kusnelzow's report that a few crystals of CaSO4 were found near the entrance oJ the bight, and that they became more frequent farther in the interior. The. bottom of the bight, proper had a crust of crystallised glauber salt Ift in thickness. This natural treasure of Na2RO4 lias been estimated at 1000 million tons. The bay is well sheltered ; many ships cross the Caspian already, from the Volga to Baku and the Persian ports , there is the railway line to Samarkand, starting farther south from Osunada. Fuel, mazut, tho distillation residue of tlie petroleum, is plentiful at Baku. Tho almost uninhabited Ust I'rt, the land between the Caspian Sea and the Sea of Aral, may become a manufacturing country — Engineering.