Let us consider the pigment known as white lead first. This is produced by causing metallic lead, which is of a bluish-gray color and very heavy, to change from its original form by a process which is known as “corrosion.” This corrosion is brought about by first taking the metallic lead, which at this stage exists in large pieces known as “pigs.” These pigs of lead are melted in a furnace and then molded into small, thin shapes which are buckles. [Illustration: HOW WHITE LEAD IS MADE FILLING THE STACK WITH LEAD BUCKLES.] [Illustration: LEAD BEING TAKEN OUT OF THE STACKS. The next step is to take an earthenware vessel, which resembles an ordinary stone crock, and first pour into it a small quantity of acetic acid, which is about the same as table vinegar. Then the crock or pot is filled up with the lead buckles. Where this white lead is made in a large way many thousands of these pots are placed in a building, the sides of which are walled up tight, the spaces between the crocks being filled in with tan bark. After the floor has been covered with a layer of these crocks, the layer is covered with boards, in order to provide a foundation for setting in the next layer of crocks and tan bark. The layer of boards also serves as a floor to keep the tan bark from falling into the open crocks on the tier below. This procedure is followed with tier after tier until the building is completely filled. Corrosion of the metallic lead in the pots now begins, because the tan bark generates some heat, becoming finally quite warm. This heat causes the acetic acid or vinegar to throw off vapor or steam, which attacks the metallic lead, causing it to decompose or corrode. This process goes on for many weeks (sometimes as much as fifteen or sixteen weeks), until those buckles of metallic lead have become a mass of white powder and nearly all trace of the original metallic lead has disappeared.] [Illustration: A LEAD BUCKLE AFTER CORROSION.] [Illustration: A LEAD BUCKLE BEFORE CORROSION.] [Illustration: HOW OXIDE OF ZINC IS OBTAINED WASHING THE LEAD. SCREENS COVERED WITH CLOTH REMOVE ALL FOREIGN MATTER. After these many weeks have passed, the pots containing the white powder of carbonate of lead, as it is called, is taken out of the building where corrosion took place, and the white deposit is put through an elaborate system of refining, which is called “washing,” and, in fact, is really washed in water, and is then dried in very large copper pans. After being dried it is in the form of large white cakes, resembling pieces of chalk. These cakes are then passed through a mill, which grinds them to very fine powder, which is packed in barrels ready to be shipped and used by the paint-maker.] [Illustration: FURNACE WHERE THE SULPHUR IS ROASTED OUT OF THE ORE.