Dust at the rollers and wash becks is usually checked by preliminary immersion of the tray of corrosions in a trough of water, but the extra weight of the water causes this sometimes, in the absence of mechanical arrangements for immersion, to be done perfunctorily. Where there are rollers, the tray is inserted in a small opening above them, the contents saturated by a spray, and then tipped over. This method also may fail to control the dust, as, unless the men engaged in washing the corrosions in the wash beck keep the mass tipped in from piling up in a heap, the contents of the trays are discharged on to the heap, and not into water. In some factories exhaust ventilation at the rollers or wash becks has been necessary. During subsequent wet processes of grinding danger is mainly from splashing. From the settling tanks the white lead is pumped into filter presses, and the resulting cake is dried. Here the considerable risk from splashing is again almost unavoidable. Concrete floors are necessary. Emptying the stoves involves much handling, with inevitable creation of dust, especially when the bowls are withdrawn from the racks. Risk has been greatly lessened by reducing the height of the shelves to 10 feet and prohibiting the piling of one bowl upon another. Mechanical drying stoves into which men need not enter either for filling or drawing are now commonly met with. Of these there are various types--(1) Horses similar to those common in laundries, which can be withdrawn on rails; (2) small chambers built up one upon another somewhat in the form of gas retorts in a gasworks, heated by steam jackets and coils, each chamber containing only two or three cakes of white lead pulp, the cakes themselves being removed by a mechanical process from the press into the drying chambers; (3) bogies carrying the white lead in bowls on racks made to pass through the tunnel-like stove; (4) drying machines--_i.e._, closed cylinders fitted with a series of platforms so arranged that they may be charged with white lead on one side, and so fixed as to be turned round by means of mechanical appliances. When dry, the material is discharged into a chute by a series of scrapers into a small enclosed compartment, holding the barrel to be filled. With the drying machine, however, there is considerable risk of dust leakage, especially when the doors are opened. In packing by hand, safety depends on efficient exhaust ventilation when the contents are tipped into the barrel, but a danger constantly present is that, to get through the work quickly, the bowls may be withdrawn from the influence of the exhaust before the last traces of dust have been removed from the bowl. Mechanical packing, by means of a large bladed screw forcing the white lead into the barrel, which as it becomes filled is lowered automatically, is everywhere desirable. An essential condition of this method is that a dust-proof collar should connect the automatic packer with the barrel. Some dust