343 



NATURE 



[Mav 20, 19C9 



Radium emanation, produced in a week from about half 

 a gram of radium bromide, is frozen with liquid air, freed 

 from hydrogen by pumping, and introduced into a fine 

 capillary tube. This is connected with an apparatus for 

 compressing the gas ; at ordinary temperature the gas 

 liquefies to a colourless liquid of high density, which phos- 

 phoresces strongly — more strongly than the gas. At about 

 70° the liquid freezes to a solid, which, when further 

 cooled, phosphoresces witli remarkable brilliancy. The 

 Rev. H. V. Gill, S.J. : A new kind of glow in vacuum 

 tubes (see p. 35S). — The National Physical Laboratory .- 

 (i) Electrically heated laboratory muffle furnace {Mr. W . 

 Rosenhain). The special feature of the furnace is the high 

 degree of heat insulation aimed at, together with ready 

 access to the working parts. The muffle attains a 

 temperature of 920° C. with a current consumption of 

 9 amperes at 105 volts, and the platinum winding shows 

 no signs of deterioration after months of continuous use. 

 (2) Quadrant electrometer for alternating current power 

 measurements of high precision (Mr. C. C. Paterson and 

 Mr. E. H. Rayner). (3) Standard non-inductive water- 

 cooled manganin tube resistances of o-ooi, 0-002, and 0-04 

 ohms respectively, to operate with currents of 2500, 1000, 

 and 100 amperes respectively {.Mr. C. C. Paterson and Mr. 

 E. H. Rayner). (4) Metallic filament electric glow-lamp 

 for photometric substandard {Mr. C. C. Paterson arid 

 Mr. E. H. Rayner). (5) Apparatus for testing definition 

 and for determining the variation of light intensity in an 

 image due to diffraction {Mr. J. de Graaff Hunter). 



Prof. W. F. Barrett, F.R.S. : (i) Apparatus (a) for deter- 

 mining the light-threshold of the eye, and (fc) for measur- 

 ing the amount of light irregularly reflected from rough 

 surfaces. (2) New form of optometer for the examination 

 and measurement of defects in vision. Optometers have 

 hitherto been defective owing to the impossibility of pre- 

 venting involuntary accommodation of the observer's eye. 

 In the present instrument this difficulty is overcome by 

 the use of an inclined semi-transparent mirror in the eye- 

 piece. By changing the attachment both pupillometric 

 and entoptic examination of the eye can readily be carried 

 out. — Prof. Silvanus P. Thompson, F.R.S. : (i) Experi- 

 ments on the contraction, by heat, of india-rubber. India- 

 rubber, under tensile stress, contracts strongly when its 

 temperature is raised. Work is done by its contraction at 

 the expense of the energy of the heat. Hence, it would 

 be possible to construct a thermal engine in which the 

 working substance is india-rubber, instead of steam or 

 hot air, and operating by contraction, instead of ex- 

 pansion, of the working substance. (2) Standard magnets 

 for quantometric work. 



Mr. T. H. Laby and Mr. Horace Darwin, F.R.S. : A 

 string electrometer, used to measure minute quantities of 

 electricity, and as an oscillograph. — Mr. T. H. Laby : 

 The counting of a particles (electrically charged helium 

 atoms) by Prof. E. Rutherford's method. By an electrical 

 method a deflection of an electrometer is obtained as each 

 a particle passes into a cylinder. A wire is supported in 

 the axis of this narrow metal cylinder, from which it is 

 electrically separated by a guard-ring insulator. This 

 ionisation chamber is enclosed in a sealed glass tube, and 

 the air exhausted to a small pressure (4 mm.). A tap 

 admits o particles from uranium, which pass into the 

 cylinder and ionise the air in it. To detect these ions, 

 Prof. Rutherford multiplied them by producing others 

 from them by collision. The field between the cylinder 

 ( — ) and the wire (connected to the electrometer) is adjusted 

 of such intensity that the first-formed negative ions 

 travelling to the wire produce others by collision with 

 the air molecules. Thus, when an o particle travels 

 through the cylinder lengthwise, many negative ions reach 

 the wire, and so the electrometer, the string of which is 

 suddenly deflected, but returns, as it is connected to earth 

 through a high resistance of thin rubber. — Mr. A. W. 

 Porter : Electric splashes on photographic plates. A 

 photographic plate is backed by a plate-electrode, and a 

 single spark discharge is allowed to pass over the plate 

 from a second electrode in front ; the plate is then 

 developed. The new effects exhibited are brought about 

 (i) by diminishing the pressure of the surrounding atmo- 

 sphere ; (2) by replacing it with other gases ; (3) by placing 

 NO. 2064, VOL. 80] 



the plate in a magnetic field. — Dr. C. I'. Drysdale : 

 (i) Vacuum tube model, showing the propagation of 

 alternate currents in a heli.x (see Phil. Mag., November, 

 1908) ; (2) stroboscopic apparatus for measuring speed, 

 frequency, slip, and other periodic phenomena. — Mr. A. 

 Wright : An electrical device for evaluating algebraical 

 formulae and equations. The device consists in the com- 

 bination of special rheostats attached to slide rules and 

 a Wheatstone bridge, by which quantities can be multi- 

 plied, divided, added, or subtracted simultaneously, and 

 by which complicated algebraical expressions or equations 

 can be evaluated or solved with an accuracy comparable 

 with that attainable by ordinary slide rules. 



Mr. C. E. S. Pnillifs : The flow of sand through tubes. 

 The rate at which the free surface of a column of sand 

 descends in a vertical tube, owing to the escape of powder 

 from an orifice at the lower end, is independent of the 

 head of sand above the opening. ^A/r. A. Malloch, F.R.S. : 

 Engine worked by stretched india-rubber. The model 

 illustrates a method whereby a long stretched india-rubber 

 cord can be made to produce mechanical work (see p. 358). 

 — The Daimler Company, Coventry: A 38-horse-power 

 Daimler engine. .\ sectional " valveless " engine, bore 

 124 mm., stroke 130 mm., showing action of piston, 

 sliding sleeves, and other working parts. 



Mr. S. Cowper Coles: (i) Specimens of metallic para- 

 bolic reflectors, made by electro-deposition, and specimens 

 of electro-deposited metals showing their crystalline struc- 

 ture ; (2) working model of an apparatus for uniting 

 aluminium by means of the formation of a flexible skin 

 of oxide. — Messrs. Strange and Graham, Ltd. : A process 

 of making ribbon metals. The molten metal is caused to 

 flow through one or more nozzles in a thin stream upon 

 the periphery of a rapidly rotating water-cooled drum. 

 The metal solidifies immediately, and is thrown off from 

 the surface of the drum in the form of a continuous and 

 uniform ribbon. It is possible to obtain metal as thin as 

 i/iooo inch, and half a mile to a mile of ribbon can readily 

 be obtained from each nozzle per minute. Ribbons of 

 aluminium, lead, zinc, tin, copper, silver, gold, &c., were 

 shown. — Mr. C. E. Larard : Cylindrical specimens twisted 

 to destruction. These specimens (principally of mild steel 

 and a 3 per cent, nickel steel) were before testing divided 

 into unit distances by circular divisions, and in addition 

 six generating lines were painted and scribed at equal 

 distances along the surfaces. The final configuration of 

 the cylindrical surfaces after fracture, as revealed by these 

 division lines, shows clearly the surface flow of the 

 material during the plastic stage of the test. — Sir Robert 

 Hadfteld, F.R.S., and Messrs. Hadficld, Ltd.: Elements 

 and alloys used in steel manufacture; high-speed tool 

 steel, caps for projectiles, &c. 



Prof. Threlfall, F.R.S. : Curves, showing that the spon- 

 taneous combustion of cargoes of coal loaded in English. 

 Scotch, and Welsh ports practically occurs only with 

 summer loadings. It was shown by the New South Wales 

 Royal Commission on the Spontaneous Combustion of Coal 

 Cargoes (1897) that ships the cargoes of which took fire 

 had mostly been loaded in summer. In view of the high 

 summer temperature of Newcastle, New South Wales, this 

 was only what might have been expected, but it does not 

 seem_ to have been noticed that a similar relation inight 

 obtain for cargoes loaded in the temperate climate of the 

 United^ Kingdom. An analysis of 4898 long voyage ship- 

 ments in the years 1873, 1874, and 1875 — presented to the 

 English Royal Commission of 1876 — shows unmistakably 

 that it is only cargoes loaded in summer which are liable 

 to spontaneous combustion. — Prof. H. B. Dixon, F.R.S. : 

 Photographs showing the generation and nature of 

 " explosion-waves " in gases. The photographs were 

 taken on films moving with a uniform downward velocity 

 (between 50 metres and 80 metres per second). The ex- 

 plosions, started by electric sparks, travelled along hori- 

 zontal glass tubes. The photographs obtained are thus 

 compounded of the horizontal movements of the flame and 

 the vertical movement of the film. This analysis reveals 

 (i.) the slow initial movements of the flame ; (ii.) the 

 sudden setting up of the " explosion-wave "; and (iii.) the 

 remarkable effects of " reflected waves." Explosive gas 

 mixtures were also fired by rapid compression with a 



