Chemistry and Physics. 371 



Silver nitrite, similar to the last 



Silver hippurate, an excessively faint image with much iiTeuu- 

 lar reduction. 



The following substances showed (with the above mentioned 

 exposures) no trace of a latent image : 



Silver salicylate. Silver tungsMte, 



" valerate, " ferrocyanidt, 



" succinate, " nitroprusside, 



u sulphite, " chromate, 



" resinate, " carbonate, 



" phosphate, <( oxalate. 



u metaphosphate, 

 As these experiments were strictly limited to the subject 

 under investigation, viz: production of latent images capable of 

 development by the action of pryrogallol and ammonia it must 

 be understood 'that t! :en of is insensitive- 



Was to this particular action with a rather brief exposure, and 

 under the conditions mentioned. And this action is that to 

 which the iodide, bromide, and chloride, exhibit their highest 

 degree of sensitiveness, rendered evident by an exposure very 

 much shorter than that given in these investigations. 



As respects the action of tannin, which action was separately 

 investigated with respect to every one of the above salts, it 

 appeared that no substance, insensitive in the abseneeof 

 acquired sensitiveness by its presence. It was also doubtful if 

 in any case tai uin innva-cd the sensitiveness of any of these 

 • : fact which, in view of the increased sensitiveness 

 conferred by tannin on the silver haloids, is remarkable. 

 Philadelphia" March 22, 1877. 



1. Chemical Actions of the Silent Electric Discharge.- Beethe- 

 lot has published in full his memoir on tl 

 actions which he has observed to be produced by the silent elec- 

 harge (effluve electrique). The first part treats of the 

 absorption of nitrogen by organic substances under ti. 

 tions, and has already been noticed in these pages. The second 

 part r.v.-,t> ,;' tl„ same ■' sorption under the influence of atmos- 

 pheric electricity, the experiments being mad 

 cal Observatory of Montsouris, one armature of the apparatus 

 being put in contact with the earth and the other with a layer ot 

 air two meters above it, the differ, 



i of a Thomson-Branly electrometer. 



Tweh 



employed, in five of which moistened filter paper was placed, in the 



