86 



Intelligence and Miscellaneous Articles. 



= tangent of the deflection. Columns second and third are ex- 

 pressed in arbitrary scale-divisions. 



Exterior 



Resistances, 

 in ohms. 



Calculated 



Experimental 



Ratio of 



Ratio of 



value of i. 



value of i. 



Intensities. 



Tangents. 



1500 



1242 



1375 







2000 



1033 



1055 



1-06 



1-03 



2600 



954 



990 



1-06 



1-04 



3000 



767 



825 



1-06 



1-04 



3500 



673 



770 



Ml 



1-05 



4000 



613 



660 



1-05 



1-03 



4500 



558 



649 



1-05 



1-07 



5000 



514 



550 



104 



1-03 



It will be seen by comparison that, with large resistances exte- 

 rior to the galvanometer-resistance and appreciable in connexion 

 with it, the laws of the division of currents practically hold, and as 

 the exterior resistance approaches that of the galvanometer the 

 coincidence with the laws is more marked. 



From the above it appears that, under certain conditions, an in- 

 duced current does not divide according to the laws of divided 

 circuits, but approximates to these laws when there is a resistance 

 exterior to the galvanometer which is appreciable in comparison 

 with that of the galvanometer. — Silliman's American Journal, May 

 1873. 



ELECTRICAL FIGURES ON CONDUCTORS. BY H. SCHNEEBELI. 



M. Schneebeli has investigated the conditions on which depend 

 the dimensions of Kundt's electrical figures, which result from the 

 adhesion of a fine insulating powder upon a metallic conductor from 

 which a discharge has just issued*. In his experiments, the dis- 

 charge of a Ley den jar took place between a horizontal metal plate, 

 sprinkled with Lycopodium-powder (for the production of the elec- 

 trical figures), and an electrode in the form of a knob, cone, or 

 point surmounting it. The author has found, like M. Kundt, that, 

 cwteris paribus, the diameter of the figure increases with the distance 

 of the electrode from the plate, but not in a constant ratio ; the line 

 which represents the ratios is not straight, but an undulated curve. 

 Also the size of the figure augments with the quantity of electricity 

 which produces it. 



When the electrode is composed of a certain number of points, a 

 circular figure is formed beneath each of them. If a small disk of 

 glass is interposed in the path of the discharge, there is produced 



* Kundt's figures are produced with great neatness on the positive 

 electrode, but are only obtained with difficulty upon a plate serving as the 

 negative electrode. That physicist found that the diameter of the figures 

 increases with the length of the discharge, and in proportion as the dia- 

 meter of the opposite electrode to the plate diminishes (Archives des Sci- 

 ences, 1869, vol. xxxv. p. 212). 



