The men are pouring hot copper into moulds for castings.] After the ore has been through all these experiences, it comes out looking like dark-colored sand or coarse brown sugar. It is not interesting, and no one who saw it for the first time would ever fancy that it was going to turn into something beautiful. It is dumped into freight cars and trundled off to the smelting furnaces. But however uninteresting it looks, it is well worth while to follow these cars to see what happens to it at the smelters. First of all, even before it goes into the smelting furnace, it must be roasted. There is usually sulphur combined with the copper, and roasting will get rid of much of it. In some places this is done by building up a great heap of ore with a little wood. The wood is kindled, and by the time it has burned out, the sulphur in the ore has begun to burn, and in a good-sized heap it will continue to burn for perhaps two months. Such a heap is a good thing to keep away from, for the fumes of sulphur are very disagreeable. Indeed, they will kill trees and other growing things wherever the wind may carry them, even several miles away. The managers of mines of copper as well as of gold and silver have learned to economize; and it has been found that instead of letting these fumes go into the air, they may be made to pass through acid chambers lined with zinc and full of water. The water holds the fumes, and can be used in making sulphuric acid. After the ore has been roasted, it is put into the furnace for smelting. If you should make an oven and put into it a mixture of wood and roasted copper, that would be a smelting furnace. Set the wood on fire, pump in air to make the flame hot, and if your furnace could be made hot enough,--that is, 2300 deg. F., or about eleven times as hot as boiling water,--you could smelt copper. Of course the furnace of a real smelting factory will hold tons and tons of copper ore and has all sorts of improvements, but after all it is in principle only an oven with wood and ore and draft. Another sort of furnace, which is better for some kinds of ore, has a grate for the fire and a bed above it for the copper.