December 15, 1923] 



NA TURE 



^77 



activities of the Weather Bureau and its weather 

 forecasts. There are many industries helped by 

 rainfall, while others are hindered. Weather changes 

 such as heat and cold, fog, hail, and squally conditions 

 are referred to as influencing general trade and 

 joumeyings. In confirmation of good work done, 

 reference is made to the death roll of the pearling 

 fleet in Western Australia ; the lives lost in 1887 

 numbered 200, while in 1910 the deaths had decreased 

 to 40. For the improvement of flood and storm 

 warnings as well as the ordinary forecasts for the 

 general public, reports are badly required from more 

 land stations as well as from ships at sea. The 

 Government jNIeteorologist deplores the want of funds 

 for the purchase of instruments required for observa- 

 tional work. Data are available for aviators, but 

 funds are required for their publication, and tracks 

 of hurricanes and storms in Australia and the neigh- 

 bouring sea, in the South Pacific, for which data 

 exist, require printing for the guidance of navigators. 

 There are 484 climatological and 5922 rainfall stations 

 distributed throughout the Commonwealth and the 

 immediate neighbourhood. Pilot balloon ascents 

 for upper air research during the year numbered 

 1049 ; the observations show great turbulence of the 

 atmosphere in the Melbourne region, owing to 

 Melbourne being situated largely in a basin, almost 

 surrounded by hills. 



New Dissecting Microscope. — Messrs. R. and J- 

 Beck, Ltd. (Cornhill, E.C.3), have submitted one of 

 their crescent dissecting microscopes for our inspec- 

 tion. The base consists of a heavy crescent-shaped 

 casting with a central pillar for the lens and end- 

 pieces supporting the hardwood hand-rests and thick 

 glass stage. The lenses, which may be either simple 

 or achromatic, are carried in a swinging arm fitted to 

 a solid rod which moves up and down the central 



gillar by a rack and pinion for focussing, the milled 

 ead actuating this being set at a convenient angle. 

 The range of motion is more than three inches. Below 

 the .stage and swinging in gimbals is a mirror, one 

 surface of which is silvered ; the other is of opal white 

 glass. The hand-rests are very comfortable and the 

 whole instrument is very stable, so much so that it 

 can be used as a compound microscope by attaching 

 a microscope body to the swinging arm. 



Action of Sodium Arsenite on Photographic 

 Plates. — When commercial sodium arsenite is applied 

 to a photographic plate it renders it developable, 

 and so, apparently, produces the same change in it 

 as exposure to light does. Liippo-Cramer suggests 

 that the change is of the nature of the production 

 of traces of an unstable complex, which provides 

 the necessary starting places for initiating the action 

 of the developer. Mr. Walter Clark of the British 

 Photographic J^esearch Association maintains that 

 this suggestion is wrong and that the evidence which 

 he brings forward in a recent communication {British 

 Journal of Photography, November 23) is in favour 

 of his contention that the developable condition is 

 brought about in this cas6 by the action of the 

 arsenite " on material other than silver bromide 

 which is present in or adsorbed on the silver halide 

 grain." Mr. Clark finds that a preliminary treatment 

 with chromic acid " lowers to an enornious degree 

 the sensitivity of a plate to arsenite solution," and 

 argues that the formation of complexes would not 

 be affected by this treatment. He finds that sodium 

 arsenite of the formula NaAsOj (or NaHjAsOg) does 

 not react with silver bromide; he gives the char- 

 acteristic curve produced by treating the plate with 



NO. 2824, VOL. 112} 



the arsenic solution for increasing times, the equi- 

 valent of increasing exposures to light, and other 

 interested details connected with this subject. 



IMOller X-ray Spectrograph. — The now numer- 

 ous applications of X-ray spectrometry'^ are provided 

 for in a new X-ray spectrograph designed by Dr. 

 Miiller and constructed by Messrs. Adam Hilger, Ltd. 

 (75a Camden Road, N.W.i). The instrument is 

 described in a pamphlet of a scientific quality and 

 accuracy which merit high praise. Dr. Miiller's 

 instrument is of simple design, and possesses an 

 accuracy sufticient for the great majority of work. It 

 provides for the oscillation of the crystal by means of 

 a clockwork motor, the normal working conditions 

 being about 40 oscillations per hour through an angle 

 of about 12°. Insulated levelling screws and a pro- 

 tective lead screen are provided. The spectrograph 

 is available for any of the three standard methods. 

 For the Bragg method (single crystal) the slit consists 

 of two brass blocks 26 mm. long, which are clamped 

 at a known distance apart. The plate holder is 

 designed to take plates 4£ in. x | in. For the Debye 

 method, a powder holder is mounted in place of the 

 crystal carrier. The slit is replaced by a brass block 

 containing a circular aperture i mm. in diameter, 

 which points at the powder holder and fits into an 

 aperture of a circular camera, 6 cm. in diameter, 

 bearing a photographic film. A small further change 

 makes the instrument suitable for taking photographs 

 by Hull's method for powders. The spectrograph 

 should prove very useful to crystallographers for. 

 information on lattice structure, to chemists for 

 analysis of materials used as X-ray targets, to metal- 

 lurgists for the investigation of the crystalline 

 structure of metals and alloys, and to radiologists for 

 measuring X-ray wave-length and composition. 



Luminescence of Boron Nitride and Calcium 

 Tungstate. — Under certain conditions of prepara- 

 tion boron nitride lights up when brought into 

 contact with the edge of a flame, and fluoresces in 

 the same spectral region under the action of cathode 

 rays. Herr E. Tiede and Frau H. Tomaschek 

 describe experiments in the Zeitschrift fur Elektro- 

 chemie, July i, 1923, which show, first, that the 

 methods of preparation which give active material 

 are those which favour the crystallisation of the 

 boron nitride, and second, that an examination of 

 active and of inactive material, by the Debye and 

 Scherrer X-ray method, proves that the active 

 material is crystalline, while the inactive is amorphous. 

 The first of these authors and Herr A. Schleede 

 describe experiments with calcium tungstate, very 

 pure specimens of which may give intense blue 

 fluorescence under the action of X-rays, with no 

 trace of phosphorescence afterwards. A minute 

 amount of impurity reduces the fluorescence, and 

 produces phosphorescence, the intensity and period 

 of which is strongly influenced by the nature of the 

 impurity and the method of preparation, as in the 

 case of the sulphide " phosphores." The fluor- 

 escence depends on the temperature at which the 

 substance is prepared, no effect being produced with 

 cold preparations, and the intensity increasing up 

 to the highest temperature used, 1100° C. An 

 X-ray examination showed that the active material 

 was crystalline, the interference lines becoming more 

 and more marked as the temperature of prepara- 

 tion was raised. An old specimen, prepared in the 

 cold three years ago, which originally showed no 

 fluorescence, was found to fluoresce strongly, and 

 when submitted to X-ray examination proved to be 

 strongly crystalline. 



