462 Soientifio Intelligence. 



increases, and, when constant, will be a definite indication of this 

 gaseous state. 



The necessary conditions to ensuring accuracy are then con- 

 sidered, and, in conclusion, it is stated that a research to verify 

 these conclusions has been commenced by Mr. J. H. Grindley, 

 B.Sc, in the Engineering Laboratory of Owens College, Man- 

 chester. 



10. Temperature in Geissler tubes. — Mr. R. W. Wood has car- 

 ried out a series of measurements in such tubes. The form of 

 tube permitted a bolometer wire to be moved from point to point. 

 The tubes were excited by 600 Plante cells, which gave about 

 1,250 volts. The electric current was measured by a torsion 

 galvanometer and its strength regulated by a resistance which 

 consisted of a glass tube filled with a solution of iod-cadmium in 

 amyl alcohol. The tubes were filled, in most cases, with nitro- 

 gen, although hydrogen tubes were also used. With hydrogen 

 under a pressure of rs™"^ and a current of 00015 ampere, a rise 

 of temperature of 2*5° was observed. Nitrogen under similar 

 conditions gave a rise of 21 •'7°. Curves are given of the run of 

 temperature in the stratifications, and in the anode light. — Ann. 

 der Physih. unci Chemie, No. 10, 1896, pp. 238-251. " j. t. 



11. Images in the field of a Crookes tube ; by N. Oumoff and 

 A. Samoiloff. — The influence exercised by a Crookes tube on 

 electrified bodies shows that the electric field created in the 

 interior of the tube extends also to the exterior. To study this 

 exterior action the authors replaced the photographic plate by a 

 plate of ebonite. After excitation of the tube the ebonite is 

 quickly withdrawn and the objects placed upon it are thrown off, 

 and the plate is then sprinkled with a mixture of sulphur and 

 minium. The sulphur adheres to the portions which are posi- 

 tively electrified, and the minium to those which are negatively 

 electrified. Thus the color of the spots shows the electric condi- 

 tion of the shadows, and the modifications in the exterior electric 

 field. It was found that the duration of the action of the Crookes 

 tube has an influence on the clearness and intensity of the image. 

 The authors prove that the yellow color of the image corresponds 

 to the parts of the figure directly attacked by the X-i-ays, the 

 red color to the images of the objects, and the neutral bands to 

 the shadows which surround the images in certain cases. The 

 authors attribute the efiects observed to electric fluxes proceeding 

 from the tubes and the objects in its neighborhood, together with 

 a dielectric polarization. — Phil. Mag.., October, 1896, pp. 308-314. 



J. T. 



12. Rontgen rays. — It has been suspected by various observers 

 that there are different kinds of X-rays. At a late meeting of 

 the Royal Academy of Sciences, Amsterdam, Professor Haga 

 exhibited two negatives which apparently showed the existence of 

 several kinds of X-rays. At a high degree of rarefaction in the 

 Crookes tubes the penetrating power of the rays through flesh 

 and bone is very different, so that the outlines of the bones are 



