890 



SCIENCE. 



[N. S. Vol. IV. No. 103. 



was the recipient of the highest honors that 

 Europe has to bestow, to an extent scarcely 

 vouchsafed to any other American. A few 

 only will be named here : Mem. Eoy. Soc. 

 (London) ; For. Assoc. Roy. Astr. Soc. 

 (London) ; Cor. Mem. Acad. Sci. (Institut 

 de France) ; Acad. Imp. Sci. (St. Peters- 

 burg) ; K5n. Akad. Wiss. (Berlin) ; Kon. 

 Ges. Wiss. (Gottingen) ; Kais. Akad. Wiss. 

 (Vienna) ; Bur. d. Long. (Paris). He 

 was also knighted, of the Order Pour le 

 Merite, by the German Empire, a distinction 

 never given to any other American and ex- 

 ceedingly rare even in Europe. 



Seth C. Chandler. 

 Cambeidge, Mass. 



THE INFLUENCE OF LIGHT ON THE DIS- 

 CHARGE OF ELECTRIFIED BODIES. II. 



CONNECTION BETWEEN PHOTO-ELECTRIC SEN- 

 SITIVENESS AND ABSORBING POWER. 

 WORK OP STOLETOW, HALL- 

 WACH8, ETC. 



58. The fact that water is an inactive 

 substance as regards the negative discharge 

 was shown by Bichat and Blondlot* by 

 means of an apparatus similar to that used 

 by E.ighi. Instead of a metal plate a sheet 

 of glass was used, over which a stream of 

 water was allowed to flow. In front of this 

 was placed a wire gauze. It was impossible 

 to obtain any current between water and 

 gauze by illumination, even when 80 cells 

 were used. The authors point out that 

 water is transparent to the effective rays, 

 as first shown by Hertz. 



59. Stoletowf used a method similar to 

 that of Bichat and Blondlot with various 

 colored liquids, such as solutions of Fuchsin, 

 Eosin and Fluorescin in ammonia. He 

 came to the conclusion that the effect was 

 always greatest in those liquids which were 

 capable of absorbing the active rays. 



60. This conclusion was in the main con- 



* C. E. 106, p. 1349. Beibl. 12, 605. 

 t C. E. 106, p. 1593. Beibl. 12, 723. 



firmed by Hallwachs* by more reliable and 

 systematic methods. The liquids to be 

 tested were placed in a rather large watch 

 glass, and were illuminated by an arc light 

 placed vertically above the surface. A 

 screen of quartz or gypsum was placed be- 

 neath the lamp to prevent disturbance from 

 carbon particles. Connection was made be- 

 tween the liquid and the electrometer by a 

 platinum wire, and the effect of illumina- 

 tion was measured by the rate of dissipation 

 a negative charge on the liquid surface. 

 Some of the results are given below: 



Aqueous solutions of Fuchsin \ as sensitive as 

 Cyanin j metals 



Aqueous solutions of KNO., 

 Eosin 



Haematoxylin 

 Aniline J 



less sensitive 



no effect 



Water 

 Solutions of Chromic acid 



Potassium permanganate 



Co(N03)2 



KNO3, KBr 

 Acetone, Amylacetate 



61. Some trouble was experienced on ac- 

 count of the irregularity of the arc lamp. 

 In order to be able to obtain at any time a 

 measure of its intensity, a piece of copper, 

 which had been oxydized by being brought 

 to a red heat, was kept at a fixed distance 

 from the arc, and the rate of negative dis- 

 charge from its surface measured from time 

 to time. Such a surface is much less sensi- 

 tive than one that is polished and clean, 

 but it appears also to be more permanent. 



62. Hallwachs gives one series of obser- 

 vations showing the influence of the con- 

 centration of the solution. It appears that 

 the intensity of the effect increases less 

 rapidly than the concentration. 



63. A consideration of the results showed 

 that all the liquids which were sensitive to 

 the influence possessed a strong absorbing 

 power for ultra-violet rays. The connection 

 between absorption and sensitiveness for 

 the effect does not, however, appear to be a 



*Wied. Ann. 37, p. 666. 



