"Yes, isn't it? As is true of so many other of our most clever inventions nature first showed man the path. Ground glass in its modified forms is used for many purposes now; and yet I venture to say few persons know how it came to be discovered." Just at this point the car stopped with a sudden jerk, and beckoning Jean and Giusippe to follow, Mr. Cabot got out and entered a large brick building that stood close at hand. Evidently he was expected, for a man came forward to greet him. "Mr. Cabot?" he asked. "Yes. I received your note this morning, so I brought my young charges out at once. It is very good of you to allow us to go through the factory." "We are always glad to see visitors. I will put you in the hands of one of our foremen who will take you about and tell you everything you may want to know." He touched a bell. "Show Mr. Cabot and his friends down-stairs," said he to the boy who answered his call, "and introduce them to Mr. Wyman. Tell him he is to conduct them over the works." Mr. Wyman welcomed them cordially. "We see many visitors here, sir," said he, "and are always glad to have them come. Although glass-making is an old story to us scarce a day passes that some one does not visit us to whom the process is entirely new; and it certainly is interesting if a person has never seen it. Suppose we begin at the very beginning. In this bin, or trough, you will see the mixture or batch of which the glass is made. It is composed of red lead and the finest of white beach sand. The lead is what gives the inside of the trough its vermilion color. The sand comes from abroad, and before it can be used it must be sifted and sifted through a series of closely woven cloths until it is smooth and fine as powder. Before we put the mixture into the melting pots we heat it to a given temperature so that it will be less likely to chill the clay pots and break them." "Do you really make glass by melting up that stuff?" asked Jean incredulously. The man smiled. "But isn't it all red?" "The red comes out in the melting. We have to be very careful, however, in weighing out the ingredients, for much of our success depends on the accurate proportions of the materials combined in the batch. Of course the chemical composition differs some for different sorts of glass. It all depends on what kind of glass is to be made. Then too the conditions of the furnaces vary at times, the draughts being better at some seasons than at others. We take a test or proof of every fresh melt, and you would be surprised to see how little these differ. Careful mixing of the raw materials is the first important item of successful glass-making; the second is the fusion by heat of the materials." "The batch is next melted, Jean," explained Giusippe, as they followed Mr. Wyman into the great brick-paved room where the furnaces were.