NATURE 



[September 13, 1917 



Part 2 of vol. ii. of the Memoirs of the Kyoto Uni- 

 versity contains an account of the recent measurements 

 made by Messrs. T. Takamine and S. Nitta in the 

 extreme ultra-violet portion of the spark and arc 

 spectra of a number of metals. The sparks were pro- 

 duced by the Hilger apparatus, and the arc in a vacuum 

 lamp, between poles of the metal to be investigated. 

 The spectra were obtained by means of either of two 

 Hilger quattz spectrographs, and were photographed 

 on Schumann plates. The wave-lengths were calcu- 

 lated from the measurements of the plates, the lines 

 of the silver and iron sparks as given by the Blochs 

 being taken as standards. The spark spectra of silver, 

 aluminium, gold, bismuth, cadmium, cobalt, iron, man- 

 ganese, .antimony, and thallium in the region 2000 

 to 1830 were examined, and a number of new lines 

 found for each element. In the cases of manganese 

 and platinum the whole of the lines are new. The 

 vacuum arc spectra of bismuth, antimony, and thal- 

 lium gave several new lines in the same region. 



In a paper read before the R. Accad. delle Scienze 

 deir Istituto di Bologna, in March of this year, Prof. 

 A. Righi returns to the question of magneto-ionisation, 

 already dealt with in previous papers. A beam of 

 X-rays ionises the gas between two metal plates which 

 are suitably connected to an electrometer and an 

 accumulator battery. A magnetic field can be created 

 in a direction parallel to the plane of the plates. 

 Without the latter field the voltage-current curve shows 

 the usual features of a saturated phase followed by 

 one in which ionisation by collision is prominent. 

 When a magnetic field of 430 gausses is super-imposed, 

 there is found a current decrease for the lower voltages, 

 i.e. in the earlier portion of the saturated phase, but 

 for voltages of 400 or above the current is slightly 

 increased. This is ascribed by the author to the action 

 of the magnetic field in promoting ionisation. In the 

 opinion of the writer of this note Prof. Righi 's inter- 

 pretation of his results is by no means the only one 

 which is possible, and though his ingenious experi- 

 ments are of great interest, -his theory will need 

 further support before it obtains general acceptance. 

 In particular, it will be necessary to show that the 

 increase of current is not caused by the oblique, and 

 therefore longer, paths of the ions under the joint 

 actions of the two fields. When the saturated phase 

 is passed, any increase in the distance travelled over 

 by the negative ions means more opportunities for the 

 production of further ions by collisions, and this may 

 be all that is necessary to explain the results. 



In ha Nature for August 11 M. Guillaume gives 

 some interesting information concerning the work of 

 the Bureau Intsrnational des Poids et Mesures, of 

 which institution he is director. As is well known, 

 the Bureau has custody of the primary standards 

 relating to the metric system, i.e. length and mass. 

 This involves fairly frequent restandardisatlons and 

 comparisons of the secondary with the primary stan- 

 dards. The institution also undertakes the verification 

 of the standards of other countries which subscribed 

 to the Convention du Metre in 1875. Dilatation 

 measurements also play an important part in the 

 operations of the Bureau. Two methods are used, 

 viz. the comparator and dilatometer methods, the 

 former being used for large bars (generally i metre 

 in length) and the latter for test-pieces the greatest 

 dimension of which is of the order of i cm. These 

 measurements are important, not only because it is 

 necessary to know accurately the dilatation-coefficient 

 of all standards issued from the institute, but also by 

 reason of the fact that such measurements are em- 

 ployed in investigating metals and their alloys. The 

 numerous applications of the nickel-steels for indus- 

 NO. 2498, VOL. 100] 



trial purposes originated at the Bureau. It is inter- 

 esting to note that most of the geodetic survey 

 standards at present in use in the world have been 

 verified at the Bureau International on a geodetic 

 comparator (or tape bench) erected specially tor that 

 purpose. A large universal comparator is in use for 

 determining the values of the various subdivisions of 

 the metre now widely employed, the values being 

 checked to within a few tenths of a micron (0001 mm.). 

 Reference is made in the article to the important work 

 carried out by Michelson, in collaboration with Benoit,, 

 on the measurement of wave-lengths, using a cad- 

 mium lamp as standard ; and to similar experiments 

 undertaken fifteen years later by Benoit, Fabry, and 

 Perot, which agreed with the results of the earlier 

 investigations to within i part in 10,000,000. The use 

 of invar (the nickel-steel of very low expansion-co- 

 efficient), which was promoted by the researches of 

 the Bureau, has now extended to horology and 

 metrology (bars and tapes) and in other directions. 



The use of alcohol as a fuel in the internal-combus- 

 tion engine and the possibilities of manufacturing it 

 economically in Australia are discussed by Mr. W. T. 

 Rowe in Bulletin No. 8 of the Department of Chemistry 

 of South Australia. Alcohol has some obvious advan- 

 tages over petrol, such as its greater safety in storage, 

 freedom from unpleasant smell, and constant com- 

 position, but in addition Its vapour when mixed with 

 air will stand a much higher compression without pre- 

 ignltion. In suitably constructed engines the efficiency 

 per b.h.p. for alcohol is 28 to 31 per cent., as compared 

 with 16 to 20 per cent, for petrol. One of the chief 

 causes militating against the use of alcohol Industrially 

 Is the restrictions of the revenue authorities, but de- 

 natured alcohol would form a good motor spirit pro- 

 vided that methyl alcohol were not used as a de- 

 naturant. Benzol or petrol is recommended for this 

 purpose. Alcohol can be economically manufactured 

 from substances grown in Australia, and might thus 

 form a valuable industry. The supply of non-utilised 

 molasses in the whole of Australia is insufficient to 

 yield the amount of alcohol equivalent to the petrol 

 imported by South Australia alone ; considerably larger 

 quantities of straw are available, however, but Its use 

 on a commercial scale has not yet been tried. In 

 South Australia the raw materials oftering the greatest 

 promise are wheat, barley, potatoes, straw, and perhaps 

 beet, but, except the straw, these would have to be 

 specially grown to yield enough alcohol to replace the 

 imported petrol. Using wheat or potatoes, the cost of 

 raw material Is approximately the same, because, 

 although wheat contains more starch, potatoes give a 

 greater yield per acre ; in each case the total cost of 

 the spirit would be from js. gd. to 35. 6d. per gallon, 

 according to the price of the raw materials. 



In the Proceedings of the Tokyo Mathematico- 

 Physlcal Society, vol. Ix. (2) 4, Mr. Hantero Nagaoka 

 obtains equations for evaluating the maximum force 

 between two circular electric currents, and suggests 

 uses for the calculations In connection with electric 

 methods of comparing the Intensity of gravity at 

 different places on the earth. 



A NOTE on a modification of the epicycloidal method 

 of tracing the profiles of toothed wheels is the subject 

 of a note by Prof . T. Levi CIvIta In the Atti e memorie 

 of the Padua Academy, vol. xxxiii., 11 (Padua: Giov. 

 Batt. Randi, 1917, pp. 8). In it use is made of the 

 " line of action," which is the locus, traced in space, of 

 the point of contact of the wheels as they revolve. 



The catalogue (No. 168) of seconi-hand books just 

 issued bv Messrs. W. Heffer and Sons Ltd., Cam- 



