PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 929 



The two plates and the porous partition between the two liquid 

 elements being vertical, the sulphate of copper is first withdrawn 

 from the upper part of the solution, requiring frequent agitation 

 to restore the diffusion, which, for the time being, increases the 

 strength considerably. The precipitated metallic copper attaches 

 itself, in part, to the porous cup so firmly that it cannot be removed 

 without being mixed largely with the particles of the cup, and, 

 generally, spoiling it. This mixture deteriorates the metal and 

 renders it unsalable, whereas, it would otherwise be pure and 

 very valuable. 



HilVs sul])hate of copper battery has an arrangement of elements 

 quite different from the above. The porous cup is dispensed with. 

 The copper plate lies flat in the bottom of the jar, having a pro- 

 tected wire soldered to it, which comes up to the top for 'making 

 the connection. A circular flat ring of zinc hangs in the top of 

 the jar, by means of a hook screwed into its upper surface. The 

 hook terminates at the top in a binding screw. No amalgamation 

 of zinc is required. The jar is filled to a little above the zinc 

 with a solution of sulphate of zinc (white vitriol) at about 20^* 

 Baume, and two or three ounces of sulphate of copper (blue vit- 

 riol) is introduced so as to lie upon the copper plate. In a few 

 minutes the copper plate is seen to be in a deep blue liquid, which 

 is beautifully shaded off to white, in which is enveloped the zinc 

 plate, and in taking care of the battery, this is the condition to be 

 maintained. Tlie copper solution being specifically heavier than 

 the white liquid, it tends to remain at the bottom ; the two plates, 

 therefore, are each maintained in its proper element, without the 

 interposition of a porous diaphragm. As occasion requires (accord- 

 ing to the work performed), a little blue vitriol is added, and as 

 the upper liquid grows stronger, a little is drawn off and the jar 

 replenished with water. Not oftener than once a week is any 

 attention required ; once in three or four weeks the zincs should 

 be cleaned off', which may be done without disturbing the working 

 of the batteiy by cutting out three or four cups at a time in the 

 usual manner. This is, without question, the most constant and 

 reliable, and by far the most economical battery for telegraphic 

 purposes of any that has ever been used. 



As to the cost of material actually consumed in running these 

 several batteries, I have some data which is deemed reliable, from 

 which I select cases where the batteries performed about equal 

 [Am. Inst.] GGG 



