On the Manufacture of Tin-plate, 357 
and both the sides of every plate being soak- 
ed alike in the lies. In this liquor they re- 
main for ten or twelve hours standing on the 
edges, but they are turned, or inverted, once 
during that time. This operation is called 
working in the lies. 
The next operation is that of steeping in 
a mixture of sulphuric acid and water, in 
proportions which vary according to the 
judgment of the workmen. 
The trough in which this operation is con- 
ducted, is made with thick lead, and the 
interior is divided by partitions of lead. Each 
of these divisions is by the workmen called - 
a hole, and each of them will contain about 
one box of plates. In the diluted sulphuric 
acid which is in the different compartments 
of this vessel, the plates are agitated for 
about an hour, or until they have become 
perfectly bright, and entirely free from the 
black spots which are always upon them 
when they are first immersed in it. 
Some nicety however is required in this 
operation, for if they remain too long in the 
acid, they will become stained, or blistered 
by it, as the workmen term it ; but practice 
enables a careful operator to judge of the 
‘time when they ought to be removed. This, 
however, is one of the most difficult parts 
