ADDITIONAL OBSERVATIONS. 
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generally been introduced into England, and from it a 
very erroneous opinion has been formed with regard to 
the Oak timber of the United States, for the northern 
timber is much inferior to that from the southern states, 
and is never used. A cubic foot of unseasoned White 
Oak is from 58 to 60 pounds, and seasoned, 47 to 49 
pounds. White Oak timber is often brought from 'the 
lakes and used for keels and bottom planks; but for 
upper works that from the Delaware and Chesapeake 
Bay is preferred, being much stronger and more durable. 
This lake timber is principally to be found at Newport. 
From the Delaware river and Chesapeake Bay large 
quantities of White Oak are likewise shipped for the 
Eastern States, of wdiich the better class of ships are 
built. A great deal of Pine timber is also shipped from 
thence for the same purpose. 
The Quercitron is the bark of the Quercus tindoria , 
freed from the epidermis. Besides tannin, it contains a 
yellow colouring matter, which may be extracted by w r ater, 
and which, on evaporation, yields a peculiar extract to 
the amount of 8 per cent, of the bark employed. The 
tannin belongs to that variety which precipitates iron of 
a green colour. This tannin is very injurious to the 
colour, because it is precipitated by the same reagents 
with the colour, and imparts to it a brownish tint. To 
obtain the colouring matter free from it, a bladder soft- 
ened in w r ater, and cut into small pieces, freed from all 
the parts which are soluble in water, is applied to the 
infusion of the Quercitron bark, which takes up the 
tannin; or it may be precipitated by a solution of isin- 
glass. 
According to Chevreul, the colouring matter which he 
calls Quercitrin, although not a simple substance, is 
obtained by cautiously concentrating an infusion of 
