526 Intelligence and Miscellaneous Articles. 



the enthusiastic student ; and finally possess the great advantage of 

 condensing into a few lines a mass of information, which otherwise 

 would, in the continental fashion, have swelled this book to double 

 its present dimensions. 



The student of Hydrodynamics should be very grateful to the 

 author, Mr, Basset, for an elegant treatise, which will place him 

 abreast of the present state of development of the subject, 



A. G, Gbeenhill. 



LX. Intelligence and Miscellaneous Articles. 



ON THE PASSAGE OF ELECTEICITY THROUGH BAD CONDUCTORS. 

 BY HUGO KOLLER. 



T^HE author closes the imperfect dielectric to be investigated with 

 -*- a known resistance in the circuit of a voltaic battery, and 

 determines the fall of potential, which is found to be proportional 

 to the strength of the current. 



The transport of electricity through imperfect dielectrics is seen 

 to be different from that through true conductors in three points, 



1, If a current of constant electromotive force traverses a 

 condenser formed of an imperfect dielectric, its intensity diminishes 

 with the time at first rapidly, and afterwards more slowly, ap- 

 proaching a definite limit along an asymptotic curve. With one 

 and the same dielectric these changes in intensity take place the 

 more rapidly the greater the tension in the condenser, and the 

 smaller the quantity of dielectric between the electrodes. 



2, The strength of the current increases more slowly than the 

 electromotive force producing it. 



3, The apparent specific resistance of dielectrics diminishes with 

 their thickness. 



This behaviour involves deviations from Ohm's law, of which 

 the former is the more important, as the two latter may perhaps be 

 partially if not altogether referred to the difference in the variation 

 of intensity according to the dielectric tension and the thickness 

 of the condenser, 



Pollowing an indication of Maxwell, the author endeavours to 

 explain the decrease in the intensity of the current by referring 

 the apparent currents which pass through a dielectric to three 

 processes which are equivalent to currents. 



1. To dielectric displacement, 



2. To the formation of a residue. 



3. To true conduction. 



The influence of the first factor is soon exhausted, while the 

 latter is independent of the time. The author considers the 

 second, the influence of which becomes less with time, and finally 

 disappears, as a transition between dielectric displacement and 

 conduction. The quantities of electricity required for an electrical 

 displacement remain in the form of electrical energy, while the 

 quantities of electricity consumed in keeping up the conduction are 

 transformed into heat. Imperfect conductors are not able to 



