EXTRACTING COLOURING FROM DYE-WOODS, 193 
an hour at least, until it escapes out in moderate quantities at 
the top. During this time the wood swells and becomes 
penetrated by the steam; then, when the vat is rilled with 
water, it will be sufficient to heat to the boiling point, in 
order to obtain, the first time, a strong decoction. The vat is 
afterwards filled twice in succession, and made to boil as 
usual ; and in the same space of time, with less labour, a 
much larger quantity of decoction is obtained, and much 
more colouring matter extracted, 
By the two methods just mentioned, considerable time is 
required for each operation, and the wood is not entirely ex- 
hausted of colouring matter; but withM. Meissonnier's ap- 
paratus much more advantageous results are attained. 
This improved apparatus consists of a copper boiler of 
about a foot and a half in width, and about two feet in 
depth. At a short distance from the bottom of the boiler is 
a false bottom, pierced with a multitude of holes, which 
sustains the wood in the .water, and leaves an empty space 
for the boiling liquor. Into the boiler powdered wood is 
thrown, and it is covered first, with strong wire-work, and 
then with a copper-plate pierced with small holes, which 
cover is held firmly down upon the edges of the boiler by 
any suitable means. At the side of the boiler is a small 
lift and force pump, simply constructed, which draws the 
boiling water from any suitable vessel and forces it through 
a pipe into the empty space at the bottom of the boiler. The 
water afer passing through the wood and the pierced cover 
of the boiler, is run ofT into any suitable receiver. 
In our manufactory, at the side of the pump, is a boiler, 
heated with a coal fire, capable of containing 450 quarts of 
water, which is to be boiled for each operation. After fill- 
ing it, and lighting the fire, the other boiler is filled with 
powdered logwood, spread as evenly as possible, until it 
contains from 84 to 90 pounds of wood. The water having 
arrived at the boiling point is then forced into the 
space at the bottom of the vessel containing the dyewood, 
