248 
Lead 1 
From the above observations it may easily be conceiv- 
ed, that if the assaying of lead ought to be performed in 
small cupells of bone-ashes, in order that the oxydated 
metal may penetrate them, and be in part evaporated, the 
cafe is different with refining on a large scale, where it is 
necessary to accelerate the operation, and to obtain as 
much litharge as possible. 
I have already said, that the wood ashes of which cu- 
pells are made for refining on a large scale are expensive ; 
that very often a sufficient quantity cannot be procured ; 
and that besides this, part of the ashes, and sometimes the 
whole, separate themselves entirely from the sole ; which 
occasion a considerable loss. I shall add, that to give 
more weight and consistence to the cupells, it is often ne- 
cessary to mix with the ashes a large quantity of sand ; 
especially if the lead contains foreign substances, such as 
arsenic, cobalt, antimony, tin, See. If the lead be only 
arsenical, after having separated the first scum, a quarter 
of a hundred weight of iron filings or cast iron turnings 
are now and then thrown over the whole surface of the 
mass. This iron, being lighter than lead, floats over it 
and absorbs the arsenic, after which the mass jnust be 
scummed : soon after, the litharge is formed without any 
Obstacle. This method is employed in Saxony. 
The necessity of adding sand to the ashes of cupells 
must have conducted to the discovery of the following 
means, which I shall here propose. 
New Method of constructing Basons for Refining . 
Without making any change in the mason- work of the 
refining furnace, called the German, care only must be 
taken to form at the bottom a sufficient number of canals 
for the evaporation of the moisture, and to arrange them 
in the manner best calculated to produce that effect. 
These canals or spiracles must be covered with a bed qf 
