2O4 
probably occasioned by the development of acid 
matter from the saline compounds of the leaf. In 
an experiment of Mr Davy, where a plant of mint 
was submitted to electrization in the Voltaic circuit, 
its saline compounds were actually decomposed ; for 
green colouring matter, with resin, alkali and lime 
appeared in the negative vessel, and vegetable prus- 
sic acid in the positive vessel. In another experi- 
ment, a healthy plant of mint, which survived electri- 
zation, afforded, in ten minutes, alkali and lime to 
the negative, and acid matter to the positive side ; 
facts, says Mr Davy, which shew that the electrical 
powers of decomposition act even on living vegetable 
matter *. 
478. Since, then, from these facts, it appears, 
that electricity so readily decomposes the saline com- 
pounds in plants ; since the separated portions of 
these compounds so easily act on the colourable 
juices of vegetables ; and since, when light promotes 
the colouration of plants, it seems to act only through 
the medium of similar decompositions, may we not 
reasonably conclude, that, as these subtile agents 
have, on other occasions, been shewn to produce so 
many effects in common, they act also, on these oc- 
casions, in a similar manner, and by the exertion of 
similar powers ? The argument from analogy, which 
we thus desire to urge, does not hinge on one or two 
points of coincidence, but is borne out by the whole 
series of successive operations that has been now dis- 
closed ; and, if solar light and electricity be allowed 
* Phi], Trans. 1807- 
