LEGUMINOSjE. 
249 
by Charles H. Weston, Esq., in the Quarterly Journal. Ac- 
cording to this writer, the branches are cut early in the morn- 
ing, and spread out in the sun. In the afternoon, the leaves are 
so dry, that they are easily separated from the branches by sim- 
ply beating them with a stick. After this they are collected 
and closely packed in warehouses, and trodden down. As they 
are not immediately used, but are kept for some time, it is of 
importance that there be no dampness, as otherwise fermenta- 
tion would ensue, and their value be destroyed. When the 
leaves have been kept about a month, their colour is found to 
have changed to a pale lead colour, which afterwards passes 
into black. It has been ascertained, that the maximum quantity 
of indigo is obtained when the leaves have acquired the lead 
colour, and that the colouring matter is only sparingly given 
by the fresh green leaves, or when they have passed to the op- 
posite extreme, and acquired the black colour. 
After the leaves have been kept a sufficient time, they are 
transferred to the steeping vat, which is an uncovered reservoir, 
built of brick work, and lined with Roman cement, or stucco 
prepared from burnt shells, and filled with water. They re- 
main there for two hours, and are every now and then turned ; 
after which, the water having acquired a fine green colour, is 
run off, and passed through strainers into the beating vat. 
Two hours may appear to be a very short time for infusing 
the leaves. It has been found, however, that when the process 
is prolonged beyond this, a partial precipitation of the Indigo 
takes place. 
The liquor, when in the beating vat, is agitated by paddles 
for about two hours, during which the fine green colour gradu- 
ally darkens, and acquires a blackish blue. As soon as this last 
hue appears, and the froth thrown up in beating becomes more 
or less white, and the incipient separation of the particles of 
Indigo can be detected, a certain proportion of lime water is‘ 
well mixed with the liquor, and the whole is allowed to settle. 
In the course of three hours the indigo will have fallen to the 
bottom, and the supernatant liquid, which ought to be of a fine 
Madeira colour, is allowed to run off by means of cocks, placed 
at different heights. The indigo is, after this, conveyed into 
the covered part of the laboratory, where it is spread on 
strained cloth, and allowed to drain. 
On the following morning, the Indigo is put into a copper, 
with a quantity of hot water, and fire is applied. As the mass 
heatens, a quantity of scum rises, which is immediately removed, 
and, as soon as the whole is brought to the boiling point, the 
fire is withdrawn. The Indigo is then again taken to the strain- 
ers, and having been again drained, it is well worked with the 
hands, and afterwards subjected to pressure in square boxes, in 
order to get rid of as much moisture as possible. In this man- 
ner large square cakes, 'about 2^ inches in thickness, are 
