Lead . 
2.23 
The top and bottom of the spiral roll, are kept as even as 
possible, that the cover may cover them closely and accu- 
rately. Sometimes sheets of lead are used flattened me- 
chanically (milled) between two rollers: sometimes, a 
caster having melted lead poured into a case of the size of 
the proposed sheets, draws it into sheets by running a 
sliding piece of wood quickly along the edges of the 
frame or mould, and pushing the melted lead before it, 
thus forms it into a sheet. 
The lead is then ready to be carried into the corroding 
room. 
This room, is furnished with earthen pots which should 
be of stone- ware. They should be wide enough at top 
to hold a spiral roll of lead, which must rest on a ledge 
within side the pot about one-third or half of the way 
down : the pots may conveniently hold from one to three 
quarts of good vinegar, according to the size of the spiral 
which fills the top. The smelter or caster, making has 
sheets according to the size of the pots which the manu- 
facturer thinks it convenient to use. The vinegar just 
reaches the under side of the ledge on which the spiral 
roll stands. The pots are placed on a layer of about 
three or four inches of horse dung, not quite close to each 
other all round the room, leaving a gang way in the mid- 
dle. The lowest tier are then imbedded up to their necks 
in fresh horse dung, or tanner’s bark. A piece of lead is 
then placed on the top of each spiral roll, and is then co= 
vered with a broad board. On this board another layer 
of dung with its pots, vinegar and spirals of lead is placed 
and buried up in dung or bark : and so on, as high as 
will admit of convenient management. The top tier, 
should be well bedded in dung and covered, because, it 
answers best to be examined from time to time to shew 
when the vinegar is all evaporated, which usually takes 
place in about two months* This top tier should be well 
