6o 



NATURE 



[May 17, 1906 



sight, giving correct elevation for any variations of muzzle 

 velocity, air density, and time of flight, as arranged for the 

 6-inch B.L. gun, Mark XI., under construction at Elswick 

 for trial on H.M.S. Africa.Sir James Dewar, F.R.S.: 

 Metallic jacketed vacuum vessels. In these metallic vessels 

 filled with liquid air the vacuum is produced by the use 

 of cooled charcoal. The envelopes may be made of brass, 

 copper, nickel, or tinned iron, with necks made of a bad 

 conducting alloy. The necks can be covered with silvered 

 glass vacuum cylinders which act as stoppers and at the 

 same time utilise the cold of the slowly evaporating liquid. 

 The efficiency of the best metallic flasks is equal to that 

 of the average silvered glass vacuum vessels now generallv 

 used in low temperature investigations. Vessels of this 

 type may be useful in industrial cryogenic operations and 

 for the storage and safe transit of liquid air and oxygen. — 

 Mr. C. V. Boys, F.R.S. : A gas calorimeter (see vol. Ixxiii., 

 p. 354, February 8, 1906). 



Mr. G. F. Herbert Smith : .\ refractometer for liquids. 

 By means of this instrument the refractive indices of 

 liquid and semi-liquid substances may be easily and quickly 

 determined in sodium light to the fourth place of decimals. 

 —Prof. II'. F. Barrett, F.R.S. : Entoptiscope, for the self- 

 examination of obscurities and defects within the eye. — 

 Sir William Crookes, F.R.S. : (i) The ultra-violet spectra 

 of the metals, photographed with a quartz train of five 

 double prisms. The spectrum of pure iron used as a 

 standard. (2) Stereoscopic photographs, taken by Sir W. 

 Crookes on the occasion of the visit of the British .Associ- 

 ation to South Africa in the autumn of 1905. — Lord Blyths- 

 ~^'Ood : Photographs of certain arc spectra. The spectra 

 were produced by means of a Blythswood concave diffrac- 

 tion grating, the work being undertaken as a practical test 

 of the gratings. The radius of the grating was 10 feet, 

 the first-order spectrum being photographed. The total 

 length given was about 40 inches, from \ 2100 to \ 7400. 

 — Dr. W. Marshall Watts: Binocular spectroscope. The 

 instrument consists of a field-glass, or other form of 

 binocular, in front of the object-glasses of which two 

 exactly similar transparent diffraction gratings are mounted 

 on optically-worked plane glass. As the instrument has 

 neither slit nor collimator it is applicable, in the first 

 instance, only to luminous objects of definite form, such 

 as vacuum tubes. For ordinary observations of flame 

 spectra, or spark spectra, a metal or ebonite plate, with 

 a slit, in front of the Bunsen or spark is employed. — Mr. 

 Edwin Edser and Mr. Edgar Senior : Specimens of colour 

 photographs, and photomicrographs. The exhibit included 

 (i) I,ippmann spectrum photograph bleached after Neu- 

 hauss's method; (2) colour photograph produced by ex- 

 posing Lippmann film successively to two continuous spec- 

 trums, the red end of one being superposed on the blue 

 end of the other ; (3) three-colour photographs of coloured 

 objects, including crystals under polarised light ; (4) photo- 

 micrographs obtained through red, green, and blue colour 

 screens ; (5) photomicrographs obtained by the aid of Zeiss 

 apochromatic objective, and other objectives. 



Royal Microscopical Society : Micro-Daguerreotvpes of 

 blood, milk, and crystals, made by L^on Foucault in 1844. 

 — Messrs. R. and '] . Beck, Ltd. : Ultimate microscope re- 

 solving power with light of different wave-lengths. A 

 specimen of Amphipheura pellucida was shown under 1/12 

 oil immersion 1-25 N.A. A single filament Nernst lamp 

 on a small optical bench was the source of illumination. 

 The beam was split up Into a brilliant spectrum by means 

 of a Thorp replica grating, and any portion of the spectrum 

 can be used for illuminating the object. The experiment 

 showed that whereas the diatom Is brilliantly resolved with 

 green light, the whole structure is invisible with yellow 

 light. — Mr. Julius Rheinhcrg: (1) Production of achromatic 

 interference bands by the double grating method ; (2) photo- 

 graphs chiefly of diatoms, taken by Dr. .\. Kohler with the 

 Zeiss apparatus for ultra-violet light. — Mr. W. Rosenhain : 

 Improved metallurgical microscope designed for the examin- 

 ation of metal specimens. The base and limb are of par- 

 ticularly rigid construction, and the tube is rigidly attached 

 to the limb. The stage racks on the broad "flange of the 

 limb, and is provided with a fine adjustment placed in the 

 line of the optic axis of the microscope. The internal re- 

 flectors employed for obtaining " vertical ". illumination. 

 Instead of being carried on a detachable fitting- are inserted 



NO. 1907, VOL. 74] 



into the tube of the instrument, and are provided witb- 

 adjustlng movements which allow of complete control of 

 the lighting. Special devices for the easy attachment and 

 adjustment of oblique and other illuminators for low-power 

 work are provided, while a detachable bridge can be fitted 

 to the stage so as to adapt It for work ^vith transmitted 

 light. For purposes of photomicrography a focusing 

 motion is provided whereby the eye-piece may be moved 

 relatively to the objective. — The Director of the National 

 Physical Laboratory : (i) Photomicrographs of the polished 

 and etched surface of specimens of iron and steel taken 

 during the progress of alternating stress tests. Dr. T. F.. 

 Stanton. (2) Photomicrographs, Dr. H. C. H. Carpenter. 

 (3) An apparatus for tests on the strength of materials at 

 very high temperatures. Dr. J. A. Harker. (4) a, Picou 

 permeameter (by kind permission of Mr. J. H. Agar 

 Baugh), b, BIfilar galvanometer free from zero creep, Mr. 

 .\. Campbell. 



Dr. P. E. Shaw: An electrical measuring machine (see 

 May 3, p. 22, and vol. Ixxil., p. 495). — Sir Oliver Lodge, 

 F.R.S., and Dr. .Alexander Muirhead, F.R.S. : Wireless, 

 telegraphy apparatus for military field purposes, (i) A 

 portable pack-transport set of wireless telegraphy apparatus 

 for military field purposes, available for communications 

 across country for distances up to fifty miles, or 150 miles 

 over sea ; with electric valves employed to accumulate the 

 impulses of a small coil and battery, or small dynamo, so as 

 to give discharges of energy only otherwise obtainable from 

 a large and heavy source of electric supplv. The arrange- 

 ment needs no earth connection, nor must it have anv 

 when it Is required to work over long distances with the 

 greatest efficiency. (2) .\ vibrating needle point-oil-mercury 

 coherer with telephone receiver. — Mr. W. Diiddeli: Some 

 mechanical and electrical prtienomena occurring in the tele- 

 phonic transmission of speech. The apparatus is intenderT 

 to demonstrate as curves on a screen the simultaneous 

 movement of the microphone transmitter diaphragm, the 

 current flowing into the telephone line, the current received 

 at the far end of the line, and the movement of the receiver 

 diaphragm when sounds or speech are being transmitted. 

 The similarity of and the difference between these four 

 curves can be e.xamined by the aid of the apparatus, and 

 the distortion and attenuation produced by the resistance, 

 capacity, and self-induction of the line can be demonstrated, 

 as well as the distortions produced by the diaphragms of 

 transmitter and receiver. The characteristic shapes of the 

 curves corresponding to the different vowel sounds and their 

 dependence on the pitch on which they are sung can also 

 be exhibited. — Mr. L. H. Walter: New magnetic detector, 

 giving both alternating currents for telephonic reception 

 and continuous currents for recording or visual signals. 

 The detector is a form of differential dynamo in which 

 electric oscillations are made to act upon one armature 

 core only. — Mr. K. J. Tarrant: Photographs of electrical 

 discharges, at atmospheric pressure and in vacuo. — Mr. 

 E. G. Rivers : .\ new electric heater. The principle of 

 construction departs from that usually adopted. The 

 object in v'ew is to secure a large heating surface at a 

 moderate temperature, and the method exemplified is the 

 use of sillcated carbon upon a terra-cotta base, forming 

 an " element." These " elements " assembled togcthir 

 constitute the healer. 



Mr. J. E. Stead, F.R.S. : .\ triple alloy of tin-antimony- 

 arsenic, polished and etched, showing bright curved crystals 

 embedded in a soft matrix or eutectic. — Dr. G. T. Moody: 

 Specimens illustrating the indifference of oxygen towards 

 iron in presence of water and the effect of the admission 

 of carbonic acid. — Messrs. Wallach Bros. : Oxygen rescue 

 apparatus and other appliances, (i) The " Evertrusty " 

 oxygen apparatus, used by the rescue parties at Courri^res, 

 consisting of two oxygen cylinders filled with oxygen, two 

 regenerators through which the vitiated air passes and is 

 regenerated, and which at the same time serve the purpose 

 of ascertaining if the apparatus is in working order prior 

 to use. (2) " Evertrusty " oxygen first-aid case for use 

 in case of carbonic oxide poisoning, or after inhalation of 

 smoke, poisonous fumes, &c., consisting of oxygen cylinder, 

 reducing valve, pressure gauge, bag and mask, with back- 

 pressure valve. — Dr. O. Silberrad and Mr. H. .A. Phillips: 

 .\ series of picrates. The salts of picric acid are of interest 

 as having been the probable cause of some of the most 



