80 Scientific Intelligence. 



stitutes, lubricating oils and greases, hydrogenated fats, varnishes, 

 the candle industry, soap manufacture, and glycerine manufac- 

 ture. H. L. w. 



5. Annual Reports on the Progress of Chemistry for 191J/.. 

 8vo, pp. 303. London, 1915 (Gurney & Jackson, London ; D. 

 Van Nostrand Company, New York). — This is the eleventh vol- 

 ume of these reports which are issued by the Chemical Society. 

 It contains eleven articles dealing with the various branches of 

 chemistry, among which radio-activity is included. Each of the 

 articles has been prepared by a specialist in the subject discussed, 

 and the book is a very useful one in furnishing concise and inter- 

 esting accounts of the important results of investigations pub- 

 lished during the year under consideration. h. l. w. 



6. X-Ray Band Spectra. — As is well known, the negatives 

 of X-ray spectra taken by de Broglie show very clearly two 

 bands in the region of very short wave-lengths. These bands 

 have sharp limits on the less refrangible side, they have never 

 been resolved into lines, and they maintain their spectral positions 

 unaltered when the material of the anticathode is changed. On 

 account of these properties it has been suggested by the Braggs 

 and Siegbahn that the two bands owe their origin to the silver 

 and bromine in the photographic films. In testing this hypothe- 

 sis E. Wagner has recently brought to light some interesting 

 and important facts. 



The spectrometer used was of the rotating crystal type and 

 was especially designed to minimize the mechanical vibrations 

 arising from the driving mechanism. The most novel feature of 

 the s\ stem consisted in coupling segments of the axles with short 

 pieces of rubber tubing. The angular speed was very uniform 

 and amounted to about 10 degrees of arc per minute. Selected 

 rock-salt crystals were used as space gratings, the natural cleav- 

 age planes containing the axis of rotation of the spectrometer 

 table and being equidistant from the emergence slit of the lead 

 collimator tube and the center of the photographic plate. The 

 " hard " and " soft " X-ray tubes were provided with tungsten 

 and platinum or palladium anticathodes respectively. The nega- 

 tives obtained with exposures of seven or eight hours are very 

 clear and sharp. 



One horizontal strip of the 7-hr. negative obtained with a soft 

 tungsten bulb shows three bands, the central image, and a num- 

 ber of metallic lines. The adjacent strip was produced simultane- 

 ously by the radiations which emerged from a sheet of aluminium 

 l*4 mm thick which was placed l cm in front of the plate. The band 

 of intermediate wave-length, which was very intense on the strip 

 first mentioned, is not recorded on the second strip. The persist- 

 ence and location of the least refrangible band show that it is the 

 second order image corresponding to the band of shortest wave- 

 length. The extreme bands were supposed to be due to silver 

 and the intermediate band was ascribed to bromine. If this 

 hypothesis is correct we should expect to 6nd that a suitable metal 



