130 
Ganges of colour which vegetable infusions exhibit 
from the action of alkaline matter, that we much 
wonder the opinion has so long slumbered in obscu- 
rity, although, from the erroneous views which have 
prevailed concerning the changes which vegetables 
produce in the air, its full development could hardly 
be expected. An opinion, indeed, approaching to 
that which has been now delivered, seems to have 
occurred, more than a century ago, to M. Geoffroy, 
who attributed the green colour of vegetables to the 
combination of a highly rarefied oil with the fixed 
and volatile salts of the sap ; and this opinion he was 
led to form, from finding that a solution of the essen- 
tial oil of thyme in alcohol became green by the addi- 
tion of oil of tartar *. 
381. But M. Geoffroy, says M. Senebier, in his 
remarks on these experiments, did not see that the al- 
kali alone always produces these effects upon the e- 
tiolated parts of plants, upon their green solutions 
which have been discoloured by light, upon their es- 
sential oils, and even "upon the pale and yellow tinc- 
tures of etiolated leaves f- It is true, that, by con- 
sidering this rarefied oil as necessary to the produc- 
tion of colour, M. Geoffroy departed from, or rather 
fell short of the truth, which is the more to be won- 
dered at, as he was well aware of the effects which 
the same alkalis produce in ordinary vegetable infu- 
sions. If, however, it be allowable to substitute the 
term colourable matter for essential oil, or to const- 
* Mem. de 1'Acad. Roy. an. I/O/, 
t Mem. Phys. Chim. t. ii. p. 17 
