May 9, 1895] 



NA TURE 



39 



Studeius' simple apparatus for determining the mechanical 

 equivalent of heat was exhibited by Prof. Ayrton. The 

 apparatus enables the heat equivalent of a watt-second to be 

 exi>erimentally ascertained with an error of less than I percent., 

 without any alli)\\ance having to !je made for heat lost by con- 

 duction, convection, or radiation. It will give the result when 

 2000 c.c. of water are warmed for two minutes with a current 

 of about 30 amperes, at a pressure of about lo volts. The con- 

 ductor consisted of to feet of nianganin rolled into a thin strip 

 to give offbeat rapidly, and formed into a double grid so as to 

 be used as an efficient water stirrer. The cross section of the 

 flexible leads was such that practically no flow of heat occurred 

 between them and the grid when a current of about 30 amperes 

 is used. 



Photographs of sections of gold nuggets etched to show 

 cr)'stalline structure, were exhibited by Prof. \. Liversidge. 

 Gold nuggets, on being cut through or .sliced and polished, and 

 elchetl by chlorine water, were found to exhibit well-marked 

 crystalline structure, closely resembling the Widmanstatt figures 

 shown by most metallic meteorites, except that, in the nuggets, 

 the crystals are more or less square in section, and show faces 

 which evidently belong to the octahedron and cube. 



i'hcnomena associated with the formation of cloud were ex- 

 IJerimeiUally illustrated by .Mr. W. N. Shaw. Clouds formed 

 by mixture of two currents of air of different temperatures were 

 shown in a large glass globe. The currents were due to con- 

 vection. The motion of the clouds, gave an indication of 

 the motion of the air. Under suitable conditions the motion 

 a.ssumed a gyratory or ** cyclonic " character. A second globe 

 was arranged to show the formation of a cloud by the dynamical 

 cooling of air, consequent upon a sudden expansion equivalent 

 to an elevation of about 10,000 feet. The water globules could 

 be seen to fall slowly. A light was arranged at the back of the 

 globe to show (under favourable circumstances) coloured coronae 

 surrounding a central bright spot. Two other globes were used 

 in conjunction to demonstrate the modification which cloud 

 formation intrixluces into the dynamical cooling of air. In one 

 of the ]^air condensation diminished the fall of temperature in- 

 cidental lo sudden expansion, and the difference was indicated 

 by the final pressure-difference between the globes. 



There were two barometric exhibits, one a mechanical device 

 for performing temperature corrections in baronreters, by Dr. 

 John Shields-, and a new form of barometer, exhiliited by Dr. J. 

 Norman Collie. 



The preparation of acetylene from calcic carbide was shown 

 by Pri>f \'. H. Lewes. The combustion of acetylene for illu- 

 minating purposes attracted great attention. Calcic carbide, 

 formed by the action of carbon on lime al the temperature of the 

 electric furnace, was decomposed by water with evolution of 

 acetylene. The remarkable brilliancy of the flame produced 

 may be judged by the fact that the acetylene when consumed 

 in suitable burners develops an ilhuninating value of 240 candles 

 per 5 cubic feet of gas. 



(leneralised frequency curves were exhibited by the .Applied 

 Mathematics Department of University College. London, and 

 also compoimd frequency curves, a harmonic analyser, and a bi- 

 projector. 



Mr. T. Clarkson showed his circlographs for drawing and 

 nicasuring circidar curves of any large radius without requiring 

 ilii- centre, with examples of cur\'es. The cr)nslruction of these 

 instruments is based upon a recent discovery that it is possible to 

 rut a flat plate of steel (of uniform thickness and temper) into a 

 ' 'ttain form, which imparts to it the property of bending always 

 in!() circular cur\es. 



Mr. R. Inwards had on view exanqiles of curious mortise joints 

 ill carpentr}', all made without comi>ression or veneering, and 

 Mr. Hermann Kiihne exhibited Junkers' patent calorimeter. 



The radial cursor, a new addition to the slide rvde, was shown 

 l>\ .Mr. K. W. Lanchester. This cursor added to the slide ride 

 'iKtkes the rule applicable at once to the calculation of whole or 

 liactional jiowers, and renders it specially useful for the solution 

 'it problems in thermodynamics. 



The Cambridge Scientific Instrument Comjiany showed a new 

 Kirni of rocking microtome and a new form of spectrometer, 

 and an improved form of Donkins liarnionograph. This was a 

 modification of Donkin's harmonograph, ami draws, on a moving 

 strip of paper, a curve compounded of two simple harmonic 

 motions. 



During the evening demonstrations by means of the electric 

 lantern took place in the meeting room. 



Prof. .\. C. Haddon showed lantern slides illustrating the 



ethnography of British New Guinea. The slides illustrated the 

 physical characters of different tribes inhabiting British New 

 Guinea, some of the occupations of the people, several kinds of 

 dances, and the distribution of dance-masks. Kvidence was given 

 in supjjort of the view that British New Guinea is inhabited by true 

 dark Papuans, and by two distinct lighter Melanesian peoples, 

 one of whom may have come from the New Hebrides, and the 

 other from the Solomon Islands. 



Lord Armstrong showed some of the results of his recent 

 experiments on the electric discharge in air. The figures 

 exhibited by means of the lantern, showed various phases, 

 hitherto unobserved, of the brush discharge accompanying the 

 electric spark. They showed also the remarkable modifying 

 effect of induction on the results obtained. The luminous effects 

 were delineated by instantaneous photography, and the mechanical 

 effects by the electric action on dust plates. The spark itself 

 had to be taken in a dark box on a shunt line, as its strong light 

 and violent action would otherwise have been incompatible with 

 the photographic and mechanical methods used in the experi- 

 ments ; but nearly the same tensions were obtained outside the 

 box as within. 



THE RARER METALS AND THEIR ALLOYS} 



w 



II. 



OW turn to more complex curves taken on one plate by mak- 

 ing the sensitised photographic plate seize the critical part of 

 the curve, the range of the swing of the mirror from hot to cold 

 being some sixty feet. The upper curve ( Fig. 4) gives the freezing 

 point of bismuth, and you see that surfusion, a, is clearly marked, 

 the temperature at which bismuth freezes being 268°. The lower 

 point represents the freezing point of tin, which we knov\ is 

 231° C. and in it surfusion, /;, is also clearly marked. The lowest 

 curve of all contains a subordinate point in the cooling curve 

 of standard gold, and this subordinate point, c, which you will 

 observe is lower than the freezing point of tin, is caused by the 

 falling out of solution of a small portion of bismuth, which 



alloyed itself with some gold atoms, and "fell out" below the 

 freezing point not only of bismuth it.self but of tin. Now gold 

 with a low freezing point in it like this is fouml to be very brittle, 

 and we are in a fair way to answer the question why Vj ])er cent 

 of zirconium doubles the strength of gold, while fV per cent of 

 thallium, another rare metal, halves the strength. In the case of 

 the zirconium the subordinate point is very high up, while in the 

 case of the thallium it is very low down. So far as my experi- 

 ments have as yet been carried, this seems to be a fact which 

 underlies the whole question of the strength of metals and alloys. 

 If the subordinate point is low, the metal will be weak : if it is 

 high in relation to the main setting point, then the met.al will be 

 strong, and the conclusion of the whole nmttcr is thi.s. — The rarer 

 metals which demand for their isolation from their oxides either 

 the use of aluminium or the electric arc, never, so far .as I can 

 ascertain, produce low freezing points when they are addeil in ijmall 

 quantities to those metals which are used for constnictive 

 purposes. The difficultly fiisible rarer metals are never the cause 



1 A Friday evening discourse, delivered at the R0y.1l Institution on M.irch 

 15, by Prof. Rotierts-.'^uslen, C.B.. F.R.S. (Continued from p. 18.) 



NO. 1332, VOL. 52] 



