Method of preventing Injury 
almost covers the workmen thus employ ed, and is very 
pernicious to them. And not only in this part of the pro- 
cess 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 re- 
mains a quantity of the fine particles of white lead, which 
of course rises in removing 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 shown 
in plate 13, 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 vessel, in a groove, so as to be taken out occasion- 
ally : these boards are bored, with a centre-bit, as full of 
holes as may be, without danger of breaking into each 
other ; the size of these holes is, in the machine at large, 
about five-eighths of an inch diameter. This being done, 
the vessel is filled with water, about three inches above 
the oak boards or riddles ; the lower brass roller is now 
under water, and about half of the upper roller is under 
water also. Thus the lead coming from the stacks is 
put through the brass rollers in water, and, by raking 
the lead with a copper rake over the oak boards or rid- 
dles, the white lead passes through the riddles, and the 
blue lead remains above; which, being taken out, is 
thrown upon an inclined plane of strong laths to drain, 
where it remains about twelve hours, when the blue lead 
is ready for the furnace to be remelted ; by this means no 
