255 
of a newly discovered vegetable acid. 
crab apple, while young, is very bitter, and has little sour- 
ness : as the fruit advances towards maturity, the taste be- 
comes proportionately sour, and the bitterness diminishes. 
The young berries of the Sorbus Aucuparia also are bitter, 
contain but one acid, and even that in small quantity : when 
the berry is ripe, it contains two acids, the combined quantity 
of both is considerable, but the bitterness has in a great de- 
gree given place to a coarse astringency. 
It is not improbable, that the bitterness produced in all the 
foregoing cases, should be owing to the formation of the 
same bitter principle: and its constant conjunction with a 
vegetable acid, seems to show that there is some very inti- 
rqate connexion between them, at present unknown. 
The preceding observations are offered as mere conjecture; 
and I am fully sensible of what little consideration should be 
attached to them : they are not however entirely devoid of 
probability. An hypothesis is below the dignity of a system 
which is founded on the indestructible basis of experiment : 
and even though it be supported by the coincidence of ad- 
mitted facts, by direct analogies, and by the correspondence 
of received opinions, it should nevertheless be the beginning 
and not the end of knowledge. 
