80 Intelligence and Miscellaneous Articles. 



differences of potential. It was the same, whether the current 

 went through the whole, or half the length of the tube. The 

 constant b was found by Prof. Quincke for ordinary German glass 

 to be almost equal : 



For water 0-000055 to 0-000067 



For ethylic alcohol 0-000034 



The resistance of the liquids altered considerably during the 

 experiments. In the mean it was as follows : — 



Resistance of the Specific resistance, 

 entire column of liquid. Ilg=l. 



Water 319 . 10 7 ohms 4722 . 10 6 



Methyl alcohol 430 . 10 7 ohms 6365 . 10 G 



Ethylic alcohol 1570 . 10 7 ohms 23350 . 10 6 



If greater forces were used, water showed a sudden change of 

 resistance as soon as the electrical force P/a in the liquid exceeded 

 a certain limiting value ; the deflection of the galvanometer-needle 

 exhibited a sudden fall of potential. This sudden fall is analogous 

 to that which is observed in dielectric liquids, and is explained by 

 the sudden occurrence of an electrolytic decomposition *. The 

 limiting value of P/« for water is considerably less than for good 

 insulating liquid dielectrics. As a rough approximation we may put 

 for it the value 1*32 to 1-45 C.G.S. in the case of the whole length, 

 and 1-61 to 1-98 C.G-.S in the case of half the length. 



I found no alteration with alcohol. 



Observations on other dielectrics, as bisulphide of cai-bon, ether, 

 oil of turpentine, and rape-oil, all showed a considerable transport 

 in the direction of the positive current. I could not, however, 

 obtain constant numbers. — Wiedemann's Annalen, No. 10, 1887. 



ELECTRICAL IMPRESSIONS. BY K. TSCHECHOW1TSCH. 



If a glass plate is laid on tinfoil, and on the glass a coin, and if 

 the two metals are connected with the two conductors of an 

 electrical machine, then, as Karsten has shown, after a greater or 

 less number of turns of the machine, the coin can be removed, and 

 by breathing on the glass, an impression is produced of the coin 

 which laid on the glass. 



The author has observed that such impressions may be easily 

 fixed on glass, if, instead of breathing on the glass, it be coated with 

 a dilute solution of stearine, yellow oxide of mercury, oxide of zinc, 

 or the like in benzol. 



If the glass is covered with a thin layer of fat (vaseline is best) the 

 coin leaves directly on the glass after electrification a perfectly 

 distinct impression. 



The figures differ with the kind of electricity with which the coin 

 is charged. — Beibldtter der Physik, No. 10, 1887 (from the Journal 

 of the Russian Physical and Chemical Society, 1887). 

 * Quincke, Wied. Ann. xxviii. p. 547 



