Copperas. 447 
to saturate the liquor as in England, but only occasionally 
when it appears too acid. Some of the mother liquor of 
the former operation is always added. 
The evaporated liquor before it passes into the cry stab 
lizing pools is sent to another bason, where it remains for 
twenty -four hours to deposit a large quantity of ochre. 
The crystallizing pools are made of fir planks surrounded 
with beaten clay. It requires ten days for the solution to 
deposit all its crystals, part of which is collected on sticks 
put into the vessel, but the purest vitriol is deposited the 
last. The liquor that remains after the deposition of the 
crystals (or the mother -water as such liquors are always 
termed) is reserved, and a portion is always added to the 
boiler in the next evaporation. 
The vitriolization of the common pyrites used in these 
manufactures is a work of considerable time, more or less 
according to circumstances, but is generally several 
months before a bed is entirely exhausted. Vitriol is 
however also made in several places from vitriolic peat , 
and in this the process is much shorter. A large manu- 
factory of vitriol from this source is carried on near Beau- 
vais in France, thus described by M. Brisson. 
The peat in the neighbourhood is of two kinds, the 
common combustible peat and the vitriolic. The former 
is, as in other countries, light, spongy, and full of visible 
remains of leaves, stalks, and vegetable fibres. The vi- 
triolic on the other hand is easily distinguished by being 
heavier, harsher, and crumbly. The waters that run from 
it also deposit much ochre which readily detects the situa- 
tion. The vitriolic peat is not found uniformly in any 
relative situation with the other species, but at different 
depths from the surface to about ten feet. 
This peat is hardly exposed to the air before it opens of 
itself and becomes very dry and harsh, and soon heats even 
in small masses. To render the vitriolization more uni- 
