244 WIEDEMANN ON THE MOTION OF LIQUIDS 



When the thickness of the plate was diminished to 39 millims., 

 this ratio had the value 



^=1-92; 



t 



for a still thinner plate 2*8 millims. in thickness, it became 



?^ = l-91. 



t 



In another case the thickness of the clay plate was about 



8 millims., and the quotient— =1*72; when the thickness of 



z 



the plate was reduced to 1*7 millim., even then the quotient had 



nearly the same value as before, viz. — = 1*78. 



z 



Stronger burnt and denser clay plates allow less liquid to 



pass through with equal intensity of current, and in equal times, 



than less dense ones. The reason of this must be, that the 



fluids encounter different degrees of friction when passing through 



clay plates with wider or narrower pores. 



§6. 



Another problem to examine was the connexion between the 

 observed transference, and the nature of the liquids used in the 

 experiments. 



By the investigations of Hagen, Poiseuille and others, on the 

 efflux of liquids from narrow apertures, it has been shown how 

 essentially the quantities of liquid issuing in equal times, under 

 equal hydrostatic pressures, depend upon the friction of the dif- 

 ferent liquids in passing through these narrow apertures ; hence 

 in causing liquids, by means of a galvanic current, to pass through 

 porous partitions, a simple relation between the other properties 

 that such liquids may possess, and the quantities of them trans- 

 ported by equal galvanic currents, is scarcely to be expected. 

 In general, however, it can be shown with great certainty that 

 the quantities of different liquids transported by the same inten- 

 sity of current are greater the greater the resistance which these 

 liquids oppose to the conduction of a galvanic current through 

 them. 



The following table gives examples of this ; in it ~ always 



