20 Mr Hart's Improvement on the Galvanic Battery. 



porcelain troughs were substituted in place of wooden ones ; 

 but, independently of their being expensive, they occupy a 

 great deal of room, and are easily broken, while the strong 

 affinity of the glaze for moisture, soon renders the insulation 

 imperfect, particularly if the acidulous exciting liquid be so 

 strong as to cause effervescence. If this occurs, a shower of 

 minute globules is thrown up from the liquid, which, falling 

 on the edges of the cells, soon moisten them so completely as 

 to destroy the insulation. To this fault, as well as the diffi- 

 culty of drying the edges of the cells after they have been 

 charged, both this and the preceding troughs are liable. Dr 

 Wollaston's improvement on Mr Children's trough, added 

 considerably to its deflagrating power. His improvement con- 

 sisted in having a counterpart of copper to each side of the 

 zinc ; but still this did not remove the former objection. 

 The great advantage of his modification of the apparatus, was 

 strikingly exemplified in Mr Children's magnificent galvanic 

 battery constructed on the above principle. 



After seeing the improved battery of Dr Wollaston, and 

 knowing from experience that the copper is only partially 

 acted upon by the exciting liquid, it occurred to me, that, 

 if sides and bottoms were added to the double eopper plates, 

 they would form cells of themselves for the acidulous liquid, 

 and thus enable us to dispense with the use of troughs alto- 

 gether. 



An opportunity of proving this occurred to me last sum- 

 mer. In examining the apparatus of Anderson's Institution 

 for the purpose of causing additions and repairs to be made, 

 the galvanic part was found extremely defective ; and, to sup- 

 ply the deficiency, I gave a sketch of the battery I thought 

 most suitable, to Mr John Condie, a most ingenious mecha- 

 nic, well known for his philosophical acquirements, and at 

 present engaged in constructing new apparatus for the insti- 

 tution. 



He constructed six batteries of twenty-five triads each up- 

 on the plan I gave him, and upon trial they were found su- 

 perior to a new battery of Dr Wollaston's construction, made 

 by that excellent artist, Mr Newman, of Lisle Street, London, 

 with the same number of plates, but the plates of which con- 



