90 



Dr. G. Gore. 



All these experiments show that the movements are greatly affected 

 both by the kind and strength of the solntion. 



2: Influence of the Relative Dimensions of the Mercurial Surfaces. 



In order to ascertain whether the movements were dependent npon 

 the circumstance that the mercurial surfaces were of very unequal 

 dimensions, I immersed the extremities of the capillary ends of two 

 vertical electroscopes (of the form I have usually employed) in a 

 solution of 40 grs. of glacial phosphoric acid in 1 oz. of water, with 

 about 10 miHims. in length of the capillaries filled with that liquid. I 

 then passed a current (from a large cell of copper and platinum plates 

 in town water) down one capillary tube and up the other ; the meniscus 

 descended in the former and ascended in the latter, and in each instru- 

 ment the motion was just as free as if one of the electrodes had a large 

 surface. 



I also passed a current through a short column of mercury in a 

 vertical capillary glass tube between two portions of conducting solu- 

 tion in contact with platinum wires. With a solution of 40 grs. of 

 potassic chloride in 1 oz. of water, both below and above the mercury 

 in a tube of fine bore, and a current derived from the copper and 

 platinum wires immersed in a mixture of 1 volume of sulphuric acid 

 and 19 of water, the mercury moved by a jerk in the direction of the 

 current. To ascertain whether electro-dynamic induction affected the 

 motion in this experiment, I included in the circuit one wire of a double 

 coil of about 1,300 turns of insulated copper wire ("No. 29 "), wound 

 upon an iron axis, and closed the secondary circuit. The motion of the 

 mercury was diminished. 



The various experiments in which a short column of mercury was 

 between liquids, such as dilute sulphuric acid, solution of potassic 

 chloride or cyanide, in a horizontal capillary, a stronger current was 

 required to move it than when it was in the form of a long column in 

 the usual vertical instrument ; it also moved by jerks and only a small 

 distance. A reason why a column of mercury between portions of 

 aqueous solution in a capillary tube of the usual diameter, required a 

 current of greater electromotive force to move it, was probably because 

 the longer total length of the slender column of solution offered much 

 greater conduction resistance. 



With a solution of 1 oz. of water, and 33 grs. of cyanide of 

 potassium at each end of a column of mercury about 25 millims. long 

 in a coarse and horizontal capillary tube, with platinum electrodes, 

 and a much stronger current from the copper and platinum wires 

 immersed in a solution composed of 60 grs. of cyanide of potassium 

 and 1 oz. of water, the mercury moved to and fro, each way about 25 

 millims., and in reverse directions to those of the current. The mer- 

 cury would not move by the influence of a current from the same 



