CHAP, in.] ELECTRICITY AND MAGNETISM. 181 



cohesion is temporarily lessened, and there also appears 

 to be a decrease in their coefficient of elasticity. It was 

 thought by Edlund that a definite elongation could be 

 observed in strained wires when a current was passed 

 through them ; but it has not yet been satisfactorily 

 shown that this elongation is independent of the elonga- 

 tion due to the heating of the wire owing to the resistance 

 it opposes to the current. 



222. Electric Osmose. Porret observed that if a 

 strong current is led into certain liquids, as if to electro- 

 lyse them, a porous partition being placed between the 

 electrodes, the current mechanically carries part of the 

 liquid through the porous diaphragm, so that the liquid 

 is forced up to a higher level on one side than on the 

 other. This phenomenon, known as electric osmose^ is 

 most manifest when badly conducting liquids, such as 

 alcohol and bisulphide of carbon, are used. The transfer 

 through the diaphragm takes place in the direction of 

 the current ; that is to say, the liquid is higher about 

 the kathode than round the anode. 



223. Electric Distillation. Closely connected 

 with the preceding phenomenon is that of the electric 

 distillation of liquids. It was noticed by Beccaria that 

 an electrified liquid evaporated more rapidly than one 

 not electrified. Gernez has recently shown that in a 

 bent closed tube, containing two portions of liquid, one 

 of which is made highly + and the other highly - , the 

 liquid passes over from + to . This apparent distilla- 

 tion is not due to difference of temperature, nor does it 

 depend on the extent of surface exposed, but is effected 

 by a slow creeping of the liquid along the interior surface 

 of the glass tubes. Bad conductors, sudi as turpentine, 

 do not thus pass over. 



224. Diaphragm Currents. Professor Quincke 

 discovered that a current is set up in a liquid when it is 

 forced by pressure through a porous diaphragm. This 

 phenomenon may be regarded as the converse of electric 



