February 2, 1905] 



NA rURE 



327 



occupipd the niiilUincIs and extended to the Severn on the 

 south-west, the I lumber on the north-east, and Yarmouth 

 on (he east. The whole of this area had a deficiency ex- 

 ceeding 20 per cent. For the whole of .Scotland there was 

 a deficiency of about 8 per cent. ; this was due mainly to 

 the exceptional dryness of the east coast. Dr. Mill loses 

 tio opportunity of enliancing the value of his published 

 r:Mnfall tables, and we are glad to learn that all values 

 quoted in future will be referred to an average of thirty 

 years, 1870 99. 



Parts xi. and xii. of vol. ciii. of the Ilullctin dc la 

 Socit'ti' d'lincoiir<ii;ciiifiit contain a review, by M. L. 

 Gruner, of the nietallurgical exhibits at the St. Louis 

 Kxhibilion, and a general account, by M. H. Le Chatelier, 



of the uses of speii.il steels in indusliy. 



Till! report for 1904 of the Board of Trade on its 

 proceedings under the Weights and Measures Act contains 

 particulars of a new denomination of Board of Trade 

 standard of 50 pounds weight which h;is been made and 

 verified in consequence of representations by the Liver- 

 pool Chamber of Commerce and the Mersey Docks and 

 Harbour Board. The use in trade of this denomination 

 of w^eight was authorised by an Order in Council 

 of October 9, 1903. During the past year a number of 

 " Board of Trade " standards, the accuracy of which is 

 required by law to be re-determined once in each five 

 years, have been verified in relation to (he imperial and 

 metric standards. 



Although several investigations have been made during 

 the past six years on the deviation of the kathode rays 

 in an electric field, the true nature of the deviation has 

 not yet been satisfactorily determined. In vol. xxxv. of 

 the Silztwfishcriclilc of the Physico-medical Society of 

 lirlangen, Mr. I''. .Schneider describes experiments frotn 

 which, by excluding disturbing factors, he is able to decide 

 that the deviation is of a purely electrostatic nature, and 

 that the dark kathode space has no influence upon it. 

 Variations in the deviation caused by differences of 

 potential and by other circumstances were carefully 

 measured. The same volume of the Silsiiiigsbcrichtc also 

 contains a discussion, by Dr. A. Wehnelt, of the produc- 

 tion of negative ions by incandescent metallic oxides, and 

 an interesting account, by Dr. Ferdinand Henrich, of 

 I.iebig's life as a student at Erlangen and Paris. 



In the December (1904) part of the liitllclin <lr /« .Soca'tt' 

 d'Kncouragcmenl (vol. ciii.), M. II. Le Chatelier criti- 

 cises the method recently introduced by Mr. (iayley at 

 the Carnegie .Steel Worlts of using in the blast furnaces 

 a current of air which has been freed from moisture by 

 cooling it below 0° C. by means of an ammonia freezing 

 machine. It is contended that Mr. Gayley's paper, recently 

 read before the Iron .ind Steel Institute, contains state- 

 ments which make it improbable that the alleged economy 

 of 20 per cent, in the fuel used in this process is due 

 solely to the mere desiccation of the air. The principal 

 advantage of drying the air for the blast probably lies 

 in its giving rise to a cast containing less sulphur than 

 ordinary pig-iron, owing to the diminished formation in 

 the absence of water of hydrogen sulphide capable of 

 ,'il tacking the spongy iron. Preliminary experiments have 

 shown the probability of this view. 



We have received from the firm of Ferdinand Ernecke, of 



Berlin, a catalogue of their lanterns for optical projection ; 



this catalogue is noteworthy because of the description 



which it contains of methods for demonstrating by pro- 



NO. 1840, VOL. 71] 



jection many optical phenomena, such as interference, 

 diffraction, and the behaviour in polarised light of crystal- 

 line sections. Messrs. Ernecke, we notice, have acquired 

 I he sole right of manufacturing the various forms of the 

 Wehnell inlerrupter. 



In the course of an investigation on the anomalous dis- 

 persion of sodium vapour. Prof. R. W. Wood (Proc. Amer. 

 Acad., 1904, xl., 3(15) has observed that the vapour of 

 sodium possesses a most remarkable viscosity which makes 

 it possible to obtain at one part of an exhausted glass 

 tube a mass of the heated vapour of great density 

 separated by a high vacuum from the glass plates which 

 close the ends of the tube. The tendency of the metal to 

 distil into the colder parts of the tube is extraordinarily 

 small ; even after an hour hardly a trace of sodium vapour 

 can be detected beyond the heated portion. The vapour 

 appears to possess a cohesion similar to that of a liquid, 

 and even in a vacuum tube it seems to have a free surface. 

 Potassium, on the other hand, distils instantaneously into 

 the colder parts of the tube. The dispersion of sodium 

 vapour in the vicinity of the D-i-line of helium is almost 

 incredibly great ; if a prism could be constructed of sodium 

 vapour giving the same deviation as a glass prism of tio", 

 two lines in the spectrum, scpara§:d by a distance equal 

 to one twenty-third of that between the D-lines, would 

 appear separated by a distance greater than that between 

 the red and bluish-green of the spectrum formed by the 

 glass prism. But even this dispersion is small compared 

 with that which obtains within, say, one Angstrom unit 

 of one of the D-lines of sodium. The variation of Ihe 

 index of refraction with wave-length is shown to conform 

 throughout the range \ 2260-7500, except very close to 

 the D-lines, with the simplest form of the dispersion 

 formula developed from electromagnetic considerations 

 for a njediutn with a single absorption band. 



MM. II. MOISSAN AND CiiAVANNF. have taken advantage 

 of the production of metallic calcium on a commercial scale 

 to re-determine some of its physical properties. The speci- 

 mens which they had under examination contained from 

 99.3 to 99.6 per cent, of the metal, and were only acted 

 upon slowly by water. Calcium can be easily turned into 

 cylinders possessing a brilliant lustre, tarnishing, however, 

 as might be expected, in moist air. It is sulTiciently 

 tenacious to be drawn into wire as fine as 0.5mm. 

 diameter, and these wires were utilised for Ihe determina- 

 tion of the specific electrical conductivity, this proving to 

 be about i6 per cent, of that of silver. The melting point 

 was found to be 810° C. and the density 1.548. The inetal 

 was also utilised to prepare calcium amalgam in quantity ; 

 this is stable in dry air at the ordinary temperature, and 

 does not absorb either nitrogen or oxygen. The crystalline 

 amalgam corresponds very nearly to the compound Ilg.Ca. 

 It is interesting to note that, whilst in a recent list of 

 Kahlbaum metallic calcium is quoted at 6s. irf. for 15 

 grains, or about 9/. per oz., since its manufacture on an 

 industrial scale it can be obtained at is. (>d. per oz. 



TlIF, J.inu.MV part of L'Eiiscii;ihnunl iiiaihdmatiqiie con- 

 tains a number of papers which should prove of interest to 

 English mathematicians. Dr. J. S. Mackay, of Edin- 

 burgh, contributes an interesting account of the life and 

 works of the late Prof. Tait. Prof. Gino Loria gives an 

 account of the progress made and the methods adopted in 

 Italy in the reform of teaching of elementary mathematics, 

 and in particular geometry. Mathematical teaching for 

 engineers forms the subject of a paper by Prof. Jules 



