251 



the mercury and the negative one in the solution of the negative leg. 

 If the mercury was too deep to allow the liquid to pass, the solution 

 insinuated itself down the sides of the mercury in the positive leg 

 (the positive wire being in the solution, and the negative one in the 

 mercury) ; but by using a suitable depth of mercury, the whole of 

 the liquid flowed from the positive into the negative leg. This is 

 the usual behaviour of an acid liquid (or of one in which the nega- 

 tive flow of method 3 predominated) with a suitable quantity of 

 mercury in a V-tube. With a strongly alkaline liquid the only 

 difference of behaviour is, that when the two wires are in the solu- 

 tions of the two legs, the liquid flows from the positive to the nega- 

 tive limb (see 16), i. e. opposite to the direction of flow with an 

 acid. 



40. There is a fixed relation between the direction of the electric 

 current and the direction of each of the classes of movements ; for in 

 every case where the former is reversed, the latter also becomes 

 reversed ; but this effect is, of course, not observable in those cases of 

 method 3 where two opposite and equal motions to the centre of the 

 metallic globule exist. 



41.1 have examined the influence of the chemical nature of the 

 metallic globule upon the movements obtained by the 1 st method, in 

 the following manner. The globule of mercury was first connected 

 with the positive pole and the liquid with the negative pole for about 

 ten seconds, and then the wires placed as in method 1 ; a temporary 

 negative flow was produced for a few moments with certain liquids, 

 apparently in consequence of the mercury absorbing a minute portion 

 of an electro -negative constituent of the solution (?), and that sub- 

 stance causing a negative flow in the succeeding operation until the 

 whole of it was redissolved. The following liquids exhibited this 

 phenomenon of reversion : very dilute solutions of nitric acid, nitrates 

 of ammonia, potash, soda, baryta, strontia (not of magnesia, appa- 

 rently on account of viscosity of the mercury being produced), lime, 

 zinc, lead, cobalt, nickel, copper, and dioxide of mercury ; also 

 sulphates of ammonia and potash ; hypophosphite and diphosphate 

 of soda ; and, strongest, the alkaline nitrates ; but not dilute solu- 

 tions of caustic potash, soda, baryta, or lime ; carbonates or bi- 

 carbonates of potash or soda; carbonate of baryta; chlorides of 

 ammonium, potassium, sodium, barium, strontium, magnesium, or 



VOL. x. T 



