194 EXTRACTING COLOURING FROM DYE-WOODS. 
and driven up through the wood. In this manner, in two 
hours, the 450 quarts pass through and extract all the colour- 
ing matter from the dyewood. 
The liquor which has passed through the wood is divided 
into three distinct portions, in this manner : a first portion 
of the decoction may be 3£° Beaume ; a second, a 
third, I ; and lastly, a fourth portion of liquid very slightly 
coloured, which may be mixed with the water for the next 
operation. In this manner the most advantageous results 
are secured, as three decoctions of different degrees of strength 
are obtained at one working, without evaporation. 
When a second operation is not commenced immediately, 
the waste heat of the furnace is employed to concentrate the 
liquor. 
I will compare the advantage of this apparatus with that 
which we were obliged previously to use. 
This, in a boiler heated by fire, 140 pounds of shavings 
and 80 quarts of water were put, and the liquor was boiled 
for four hours : this was renewed three times. For 40 pounds 
of logwood, it was, therefore, necessary to boil 240 quarts 
of water for twelve hours. I double these quantities the 
better to compare them with those produced by the new ap- 
paratus. Thus, by the old method, for 80 pounds of wood 
it was necessary to boil 4S0 quarts of water during twenty- 
four hours. 
By the novel method, when from 84 to 90 pounds of wood 
are operated upon, two hours are necessary for heating the 
450 quarts of water, and two hours for pumping it through 
the wood. Therefore, for 84 pounds of wood, it will be ne- 
cessary to heat 450 quarts of water for four hours, effecting 
an economy of fuel for twenty hours' consumption. 
Besides this, the colouring matter is better extracted, and 
a great economy of labour is effected, as one man can effect 
two operations per diem. 
Several precautions are necessary, in fact indispensable, 
to ensure complete success ; for instance, the wood must be 
