350 Hare on some Improved Forms, &«. 
appeared incomparably greater. The shock from the 
Cruickshank trough was more severe. You must recol- 
lect, that in former experiments I found that galvanic 
plates, with their edges exposed as they are in the porce- 
lain troughs, used by Sir Humphrey Davy, were almost 
inefficient, when used without insulation, as the deflagra- 
tor pairs are. This demonstrates, that an unaccountable 
difference is producible in galvanic apparatus, by changes 
poles, takes place at the negative pole of the pile, and 
n inspecting the diagram, No, 3, plate 5,it may be seem: 
that by the section, each copper case, appears like two 
plates C c, of which those marked C, only appear to be 
soldered to the connecting straps. Removing the portions 
of the cases marked c, the series would be reduced within 
the definition, above given, of series used in apparatus on 
the principle of the Couronne des Tasses, in whic the 
zinc is positive. It would be surprising, that doubling the 
extent, or varying the position of the copper surfaces: 
should cause any change of polarity. 
_ The observations, which are the subject of this commu- 
nication, combined with those which you have made, of the 
