Lead 1 
225 
tion, in preference to the common mode of preparing 
white lead, I will first state what the common mode is. 
When blue lead is in part corroded in the stacks, by an 
acid raised by a considerable degree of heat, brought on 
by hprse-litter, the corroded and uncorroded lead are tak- 
en from the stacks to a room, called the engine loft, where 
a pair of iron rollers is fixed with a screen under them. 
The lead in this state is passed through the rollers and 
screen ; from the motion of these rollers and screen, by 
which the white lead is separated from the uncorroded or 
blue lead, together with the moving the lead, in order to 
its being passed through them, a very considerable quan- 
tity of fine dusty white lead is raised, which almost covers 
the workmen thus employed, and is very pernicious to 
them. And not only in this part of the process are they 
liable to be thus injured, but they are again exposed to 
the dusty lead, by removing the blue lead from the screen- 
house to the furnace, as there still remains a quantity of 
the fine particles of white lead, which of course rises in re- 
moving it ; and also, in removing the white lead from 
under the screen to the grinding-tub, a quantity of the 
dust arises, which is very detrimental to the people so 
employed. 
My invention removes all these difficulties respecting' 
the dry dusty white lead, so very injurious to the health 
of the working people ; and consists of a vessel, as shewn 
in the plate,* fig. 1 , twelve feet long, six feet wide, and 
three feet ten inches deep. In this vessel is fixed a pair of 
brass rollers in a frame, one roller above the other. The 
centre of the rollers is about ten inches below the top of 
the vessel ; and, one inch lower, is a covering of oak 
boards or riddles, an inch thick, fixed in the inside of the, 
* See the next number. 
FT 
VOL. Ill- 
