SCIENCE NOTES.

Otago Witness, Volume 25, Issue 2321, 25 August 1898, Page 54

SCIENCE NOTES.

— One of the latest applications is described in a most interesting communication 1o Ihe Academic dos Sciences de V n'is by H. Couriot, in which he states that the X rays afford an instantaneous and certain means for determining the purity of mineral fuel. The fact that the diamond and wood are both permeable to these rays, whilst gHx' m 1 ido • i'c Met. vina vi .in Ktue 111 1 veto, pei'mitted the presumption that the combustible material of "uel would be transparent to the cathode rays, the sil reous ash-forming constituents, on the other hand, obstructing the passage of the ray- and forming an obstacle the more impenetrable in piop.irtioii as their abui dtince incie.>ses i vis lv "'(he^is can bp iustified b\ :' prncl'f'il test, with a radioscopic screen and an X-ray apparatus. In every instance of the tests made by the author with anthracite, coal, lignite, peat, coke, and briauettes, the full

details of the internal structure of the m eral matter of the fuel were plainly rcvealec?, the slightest fragment of schist, invisible to the unaided eye, being shown upon the screen either as a black spot or as a dark band in the field illuminated by the rays. Coal being very transparent to the cathode rays, it is unnecessary to trim the sample 'into a regular shape, the large fragments furnished by natural cleavage sufficing for the test. The radiographs were obtained with a lOin sparking coil and a Willard tube, the exposure being for about iivc minutes, with samples measuring l^iri to 2in in thickness.

— An important paper was read at a recent meeting of the Franklin Institute on an improved method of galvanising wire and wire goods. The term galvanising as here applied is a misnomer, for the process is not an electrical one. Hitherto it has consisted in drawing the iron wire slowly through a large tank of melted zinc, and upon emerging therefrom through wipers of asbestos or other material to remove the superfluous metal. This m±thod is slow and expensive, for tho iron must be raised to the same temperature as the molten metal, and the amount of the latter is often 50 or 60 tons, in order to ensure sufficient length to the w ire to be opera ted upon. By this new syst-em the wire is placed in its original coil in the bath of molten zinc, which need not bs of extraordinary size ; and after sufficient time has been given to ensure adherence to the zinc, the coil ;s; s removed and placed in a centrifugal separator, with a speed of about 750 revolutions per minute, axe jiiij't] Hu >us metal oetng thvuwn off ; and while the coil of wire is ycthot it is submitted to -i priTig ad ion on a h'l< cV so that the various strands shall not be welded together. An alternative plan is to unwind the coil and rewind it at such a distance that the metallic coating upon it solidifies during transit. This new system, the pracdiiiuig Uun&ifc. 'J'lns. u(M\ (VjKem. tiic ji,.icticab'hiv i,f which has been rlpm.n-ii ''el by so much time, and can be accomplished by such s mple means, that it is likely to be universally adopted.

—An American scientist has invented a new form of spectroscope, made by building up steps of equal thickness of optical glass. With 20 elements, 5 millimetres thick, the resolving power is 100,000, or about that of the best diffraction gratings. It is c-,n II 1 , ■'•'>() (i ilu <■>> ■> ■" (| f single lines, and the study of the effects of broadening the shifting or doubling of the lines. — i'he cry ox a iua<ni.'ti'ii in Aladdin, "New lamps for old!" is matched in a story told by M. Philippe, of Paris. It appears that' a Russian loan of fifty million francs was taken up by ItotLschild in 1836. M. Poizat, a French chemist, discovered that the older Russian silver coins contained a large proportion of gold, and he having entered into relations Avith Rothschild's, the latter stipulated that the loan should be repaid in old silver. The unsuspicious Czar acceded, the wily chemist recovered the gold from the molted silver, and shared the profit with Baron Rothschild. The Emperor Nicholas subsequently learned the fact and &ant for M. Poizat to St. Petersburg to install a similar laboratory to deal with the remaining old coinage, hum which expedition the French chemist returned loaded with honours. This recalls the fact that Dr Emmens makes nrgentaurumfrom Mexican dollars, probably of primitive manufacture.

• — The new pendulum chronoscope is said to be the most wonderful timing instrument in the world. It measures accurately down to the one-thousandth part of a second. It can be used with the quickness of a stopwatch, and neither electrician nor mathematician is needed to operate the instrument, which is mechanical, with si7nple electrical attachments. The speed of a cannon-ball can be determined by the new timer, and it will tell the lapse of time between the firing of a revolver and the starting of a runner, or determine how long it takes a boxer to deliver a blow.

— A correspondent of Nature recently noted this singular fact in connection with strychnia. Some wheat, which had been poisoned by soaking in a solution of strychnine, and which was intended for killing sparrows, after having been kept for some time in cardboard boxes, was found to have become infected with weevils. On examination it was found that the boxes were full of weevils <vid their excrement, and the wheat was more than half eaten. Strychnine was found to be present in the wheat, and in apparently still larger proportion in the excremejit of the weevils, so that it had evidently passed through tne digestive apparatus unchanged. When so little as from half to three-fourths of a grain of the alkaloid is suflicient to kill a strong man, the difference between the role played by the alkaloid becomes very striking. It has been found that the weevil Authonumus druparum can feed with impunity on kernels containing hydrocyanic acid, while the same acid administered to caterpillars of Delopeia pulchella caused them quickly to die, although they were quite unaffected by the poisonous principle of the Calabar bean, known as eserine.

—In a recent number of the American Journal of Science, Mr JT. V. Gill has an interesting paper on " The Theory of Singing Flames." The phenomenon of a gas jet burning inside an open tube emitting a musical note is one of those facts which, although known for many years and much written about, has never been fully explained. Among the more interesting theories was that of De la Rive, who sup-" posed the sound to be due to a periodic condensation of the Welter vapour produced in the combustion of hydrogen gas. Faraday showed the inadequacy of this theory by the use of a flame which did not form water vapour, and proposed in its stead the theory that the so-called singing was caused by successive periodic explosions of a mixture of gas and- air. This was accepted by Tyndall. Another theory which has been proposed is that the sound is produced by vibrations maintained by heat, the heat being communicated to the mass of air confined in the sounding tube at a place where, in the course of vibration, the pressure changes. Sondhauss performed a series of experiments his chief conclusion being that the condition of the column of gas in the supply tube had an important influence on the phenomena. — A now fire - resisting cement lias

lately been subjected to a careful test in Germany, and an official protocol has been issued concerning its behaviour, which bears the signatures of several architects, engineers, and other experts. The trial was conducted in a wooden house built for the purpose, the walls and roof of which, and an iron girder supporting the roof, were coated with an inch-thick layer of asbestic. The structure was partly filled and surrounded outside with a mass of shavings and wood chips soaked in petroleum, and the whole was set alight and allowed to burn for about three-quarters of an hour. The fierce conflagration was then extinguished by means of hose, when it was observed that the asbestic showed no sign of either cracking or peeling. When it was at longth chipped off in various place-s, both the iron and wood of which the structure was composed were found perfectly intact. It may be mentioned here that the huge fireproof curtain which separated the stage from the auditorium at the late " greatest show on earth" at Olympia, London, was coated with asbestic.

—Dr W. J. Russell, F. 8.5., has now proceeded so far with, his discovery of a method of photographing objects without the aid of light that he is hopeful of publishing a paper upon the subject to the Royal Society at an early dote. He, has succeeded in taking no fewer than 200(7 pictures entirely in darkness. —A. I/owey and P. F. Richter energetically defend a view now held by a large number of clinicians, that fever in acute infectious diseases is one of the weapons of defence possessed by the animal body. In proof of this they detail a series of experiments on rabbits, consisting in the production of high temperature . . . and subsequent inoculation of the animals with the minimal lethal dose or its multiple of pneumococcus, hog cholera, and diphtheria. The results showed that the animals in which fever had been artificially produced lived longer than the controls ; some, indeed, survived the infection. Although indicating the curative power of fever, the authors do not oppose the proper use of the antipyretic measures, when these have favourable incidental effects (quieting the nervous system, etc.). But, they add, it may be profitable to search for pyretic agents — i.e., such as evoke an artificial rise of temperature. — Canada Loncet.

— JRecent experiments with improved instruments for measuring the velocity of projectiles have shown that the speer] goes on increasing after the missile has left the mouth of the cannon. Leaving the muzzle with a velocity of about 1474 ft in a mjcopcl, a projectile has been observed to increase ils speed to about 1689 ft per second within the first 6ft. It is only after having travelled about 25yds that the projectile's velocity becomes reduced to the speed that iL had on leaving the muzzle. This is ascribed to the impulse of the expanding gas being Ml for some distance beyond the cannon's mouth.