Feb., 1904.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



17 



prism of rock salt, about three-quarters of an inch wide, 

 as a screen. l-"irst this was turned so that one face was 

 perpendicular to the line joining T to G. On placing 

 the conductor near to T, vigorous sparking coniiiicnced 

 at G. If the prism be then turned so as to present an 

 angle, the vigour of the sparking will be diminished, even 

 though the prism be moved slightly to one side so that 

 the line joining the points would only traverse a small 

 thickness of the rock-salt. The exact explanation of 

 these phenomena is not clear. It seems evident that 



light, which can be impeded, reflected, or refracted, is the 

 origin of the effects shown. That they are not caused by 

 ordinary light, however, seems to be the case, since the 

 plates (three-quarters of an inch thick) of rock-crystal, 

 &c., interrupt the communication. The author concludes 

 that rays of ultra-violet light are the cause of the 

 phenomena. This seems a promising field for investiga- 

 tion, as the apparatus is so very simple and easily 

 applied. 



The Altimeter. 



We have received from Messrs. Newton and Co. a list of 

 their optical and other scientific instruments. .Among their 

 novelties is the .Altimeter, which has Ijeen made to supply a 

 want that has been felt anions kite t1 vers and military balloonists. 

 It is a simple form of aneroid barometer marked in figures for 

 heights, and is so devised that the hand on the dial rests at the 

 highest altitude obtained by the kite or other aeronautical 

 machine on which it has been sent up. The scale tends to 

 five thousand feet, and the full-sized instrument in an alumi- 

 nium case weighs about seven ounces. .Messrs. Xewton 

 mindful of the increasing price of radium, which makes even a 

 few milligrammes of the metal an expensive luxury, have pro- 

 duced a radium screen, which is a sheet of glass coated with 

 a mixture containing radium bromide in very small quantities. 

 The largest sized screens cost half a guinea, and there are 

 cheaper ones which are sufficient for showing many of the 

 remarkable properties of the metal. 



It is not to northern China that one would usually look for 

 an example of electrical progress, but there is at least one 

 place on the eastern shore of the Liaotung Peninsula which 

 might well set an example to many of the western towns. We 

 refer to the city of Dalny, which lies near Fort Arthur, in that 

 portion of the Chinese Empire which was leased to Kussi.a in 

 189S. Electrically, Dalny is up-to-date. It has both tele- 

 phones and the electric light. The central station, which is 

 considered the finest electric plant in Asia east of Singapore, 

 was finished over a year ago. It is eijuipped with three of 

 Ganz and Co.'s generators, with a total of looo-horse power, 

 and has a reserve space for additional machines to double its 

 present capacity when required. Dalny, besides other things, 

 is an important seaport, and has a dry dock 380 feet long, 

 50 feet wide, and iS feet deep, which is equipped throughout 

 with electric pumps. A larger dry dock is building, at which 

 electricity will also be adopted. In connection with the dry 

 dock are the harbour repair shops, with foundry, smithy, 

 machine and fitting shop, boiler shop, etc. All these shops 

 are electrically driven and lighted throughout. Dalny also 

 boasts an excellent telephone service, and altogether it may 

 fairlv claim to be one of the most progressive cities in the 

 East. 



Continental Physical 

 Notes. 



By Dr. .\i,fkI':i) Grahenwit/. 



Resea.rches irv Sola.r and Stella^r 

 Photometry. 



The accurate data we possess as to the r.itio between the 

 intensity of the dilTereut stars are due to the work of several 

 generations of astronomers. As regards, however, the ratio 

 between the intensity of the sun and that of the stars, the 

 results are far from being as satisfactory, the figures stated by 

 different observers varying up to ratios as high as i and 10. 



The knowledge of these ratios, as pointed out by Ch. I'"abry 

 (Eclair. Klec. No. 50), is, however, of the highest interest, 

 allowing as it would of determining for stars the distance of 

 which from the earth is given the ratio between their absolute 

 candle power and that of the sun. and thus of classifying the 

 sun, so to say, in the hierarchy of the stars. 



.As the light of the sun has a colour resembling closely that 

 of most of the stars, a photometric standard of the same shade 

 could be chosen, which is far from being the case in connec- 

 tion with our ordinary lamps. To this effect, l<"al)ry projected 

 the light of a glow lamp through a layer of an ammoniacal 

 solution of copper sulphate; l)y regulating either the thick- 

 ness or the concentration of the li<|uid layer, the emerging 

 light could be given a tint strictly identical with that of the 

 light of the sun. The photometric standard thus modified 

 would be compared separately, both with the light of the sun 



and that of a star when the ratio " was found to be about 



\V ega 

 6 X io"\ 



As regards the data relative to the illumination produced 

 by stars in terms of our photometric standards, the results 

 obtained are true only to within 10 per cent., on account of 

 the difficulty inherent in the dift'erence of coloration. Accord- 

 ing to Fabry, the illumination produced by the sun when in 

 the zenith on the level of the sea is about lao'ooo lux, being, 

 as a matter of course, variable with atmospheric conditions, 

 but to a smaller extent than might be anticipated, provided 

 that only days of fine weather be considered. Photometric 

 measurements will allow of ascertaining whether the sun is a 

 variable star. 



These researches will enable the photometric unit of astro- 

 nomy to be connected to that of physicists. The intensity of 

 a star should be measured by the illumination produced on a 

 surface perpendicular to its rays, being expressed in lux. On 

 the other hand, astronomers will define the same by its nuif^ni- 

 tudc, the magnitudes of two stars differing by one unit, as the 

 ratio of their intensities is 2 : 3, the most brilliant h.iving the 

 smaller magnitude. The following table records some com- 

 parative data of this kind : — 



As the most feeble stars visible to the naked eye are these 

 of the sixth magnitude, one candle ceases to be visible to the 

 naked eye at a distance of about 10 km., and a telescope 

 showing stars of the fourteenth magnitude would .allow of 

 seeing a candle at a distance of 400 km. (apart from atmo- 

 spheric absorption). 



Electric DischaLrges in the Air. 



In a paper read before the .Angers Congress of the; I'Yench 

 .Association for the .Advancement of Sciences, Proicssor de 

 Kowalski describes some experiments made by him, in con- 

 junction with Mr. Mosciki, on the chemical action of high 

 frequency electric discharges in gaseous mixture. With a 

 certain frequency, a discharge through a gaseous medium is 

 found to take a special character, which, by the way, depends 

 also on the amount of electric energy available. The chemical 

 actions of a similar discharge are very important from the 



