Chemistry and Physics. 143 



observed when the cathode rays act upon mixtures of pure lime 

 with pure rare earths. He has shown that this method of obser- 

 vation is capable of remarkable delicacy, so that it is possible 

 with the aid of the spectroscope to detect and identify in this 

 way traces of substances which would be overlooked by all 

 other means of investigation. He has now turned his attention 

 to the study of the cause of the phosphorescence of certain 

 varieties of fluorspar which show this phenomenon to a high 

 degree, and has found in the case of a chlorophane giving a 

 beautiful greenish-white light that the phosphorescence is caused 

 by the presence of various rare earths. By means of spectro- 

 scopic analysis he has identified in it the presence of gadolinium, 

 terbium, dysprosium, and samarium. In order to fully establish 

 these conclusions he then prepared chlorophane synthetically by 

 fusing together the amorphous precipitated fluorides, and thus 

 obtained products which fluoresced in the cathode ray tube much 

 more brilliantly than the natural products, and gave identical 

 spectral bands. — Comptes Rendus, cxliii, 825. h. l. w. 



5. A Comparison of the Optical Temperature Scale with the 

 Nitrogen Thermometer tip to 1600°. — The Physikalisch-Technische 

 Reichsanstalt reports contain a valuable article by L. Hol- 

 born and S. Valentineb on this subject. They conclude that 

 the melting point of palladium, determined by the nitrogen ther- 

 mometer, is 1575°. The optical method gave 1570° and 1582° 

 according as the black body was observed at stationary tempera- 

 ture with a thermoelement or with changing temperature with- 

 out the thermoelement. The melting point of platinum was 

 found to be 1790°. The errors arising from the employment 

 of the nitrogen thermometer arise principally from irregular 

 distribution of temperature of the vessel. These need not 

 exceed even at the highest temperature 10°. — Ann. der Physik, 

 No. 1, 1907, pp. 1-48. j. t. 



6. Light Impressions on Photographic Plates. — The authors, 

 P. H. Evkman and A. P. H. Tbivblli, discuss the influence of thin 

 and thick sensitive films in regard to the character of the image pro- 

 duced. They find that while the photographic images produced 

 by ordinary daylight are much influenced by the depth of the 

 sensitive film, the images produced by the Rontgen rays are not 

 affected by the thickness of such films ; moreover, wetting with 

 water a sensitive film does not modify in any way its sensitive- 

 ness to the Rontgen rays, while this process makes such a film 

 less sensitive to daylight. Many experiments were made in 

 regard to the effect of character of surface and thickness of film 

 on light impressions. — Ann. der Physik , No. 1, 1907, pp. 199-203. 



J. T. 



7. Ratio of the Energy of the Rontgen Rays to the Energy of 

 the exciting Cathode Rays. — Edna Caeteb reviews the contradic- 

 tory results obtained by various observers in measuring the 

 energy of the Rontgen rays and makes a new determination, 

 using a bolometer. With a difference of potential of 59 kilo volt, 



