MR. DANIELL ON VOLTAIC COMBINATIONS. 51 



border of compact pink copper, varying from 1 J inch to ^ inch in width, but not 

 wider at the sides than the ends ; and the remainder was covered with precipitated 

 copper of a darker red colour, into which the former graduated. On the upper 

 varnished side there were a number of little rosettes of copper, which were loose, 

 giving it a gritty feel, and which evidently proceeded from a number of minute points 

 to which the varnish had not adhered. Fig. 1. (Plate II.) may convey an idea of the 

 appearance of the precipitated copper. Both surfaces of the copper plate having been 

 cleaned, it was replaced in the solution, and the double zinc ball in the membrane, 

 instead of being placed over the centre, was suspended over that end of the oval which 

 was farthest removed from the conducting wire. The galvanometer indicated 48°, 

 and remained perfectly steady for an hour, during which the action was continued. 

 At the expiration of this time the plate was examined, and the pink copper was found 

 deposited only at the extremity under the ball, forming a segment of a circle, of which 

 the ball was the centre, but still not sharply defined, but imperceptibly shading off 

 by a darker colour to the unchanged surface at the other extremity. 



Here the efficiency of the generating ball was evidently impeded by the deficiency 

 of the conducting plate on one side. The radiation could only take place towards 

 the other side ; and although the conductor was of great extent, the increasing di- 

 stance of its several points caused it to act at a disadvantage. 



After these experiments the plate was cleaned and replaced in the solution ; and 

 in order to determine the action of more than one generating point, at a distance 

 from one another upon the same conducting plate, I first placed a single zinc ball in 

 a membrane close to the conducting wire of the plate, and found the deviation of the 

 galvanometer 42°'5. I then broke this connexion, and placed a douhle ball of zinc 

 over the farthest extremity of the oval ; the galvanometer again marked 42°'5. When 

 the circuit was completed with both together the galvanometer only rose to 45°. 

 Upon making or breaking contact with either ball singly, while the other remained 

 in circuit, the needle only varied 2° or 3°. When the positions of the double and 

 single ball were changed, the difference upon breaking the contact with it was 5°. 

 After four hours action the plate was examined, and the pink copper was found de- 

 posited in two segments of circles, of which the balls had been the respective centres; 

 and the remainder of the plate was covered with a precipitation of a redder colour, 

 (fig. 2.) This thinner precipitation gave no indications of an increased substance as 

 evidence of additional action at the points where the effects spreading from the two 

 centres must be conceived to have been superimposed. 



The plate having been once more cleaned, the double ball was placed nearly over 

 its centre, and when connected with the galvanometer in circuit it affected it 55°. 

 The single ball placed also nearly over the centre, but about two inches removed from 

 the position of the double ball, aflfected it singly 45°. When the connexion was made 

 with both the deflection increased to 57°. After four hours action with both the balls, 

 a beautiful well-defined oval of pink copper precipitate was found immediately under 



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