411 
electrical and chemical changes. 
vessel, from the action of sea water, I found that when the 
two vessels were connected by moist tow or vegetable sub- 
stances, or by a wire (even though fine) of any oxidable 
metal, the protection was complete : but when even a thick 
wire of platinum was employed, the copper, though in imme- 
diate, contact with the zinc, became corroded. After the ex- 
periment had continued several days, the surface of the 
platinum opposite to the copper was found tarnished, as if it 
had been slightly acted upon by the chlorine combined in 
the sea water ; but this effect had been too feeble to be con- 
nected with any sensible degree of electrical polarity in the 
platinum. 
This result, with those mentioned in the preceding pages, 
seems to show that there can be no accumulation of electri- 
city in Voltaic combinations, unless the same or similar con- 
ditions of chemical change exist in the elements or single 
circles composing them ; and that under other conditions, 
the power generated in single circles is either destroyed or 
diminished according to the opposing nature, or want of 
conducting power of the chain of intervening bodies. For 
instance, in the arrangement (mentioned p. 409) of one 
piece of zinc and one of platinum, the power is doubled by 
another series of the same kind, destroyed by an arc of 
platinum, and diminished by an arc of zinc; by a second 
solution and a second arc of zinc, it is diminished still 
more ; by a third it is nearly, and by a fourth absolutely, 
destroyed. 
As the chemical changes always tend to restore the elec- 
trical equilibrium destroyed by the contact of the metals 
