Page:Popular Science Monthly Volume 34.djvu/627

, with its disproportionately thick bottom, has been replaced by a beautifully symmetrical figure, the shape of an enormous test-tube. But it occasionally happens that the glass flows a little too freely, and there is danger of the sides of the tube becoming too thin. To avoid this result, the blower throws his tube into the air whenever he finds that the glass is too liquid, and thus permits it to settle back upon itself. As the tube by this time is about five feet long, in addition to the length of the pipe, itself, one can readily fancy that this apparently playful toss requires both skill and muscle. It is a fine sight to watch the graceful ease with which these brawny fellows accomplish it.

When the tube has been formed to the satisfaction of the blower—and it requires a surprisingly short time for the whole operation—he allows it to become comparatively cool. He then thrusts the rounded end into the furnace, blows into the mouthpiece of his pipe, and quickly covers the opening with his hand. Presently, a slight report is heard, like a mild explosion. The confined air, expanding with the increasing temperature, has blown a hole in the end of the softened tube. Resting his pipe on a convenient support, and still keeping the glass in the furnace, the blower gradually rotates the tube. Under the influence of centrifugal force, the hole grows larger and larger, until the tube becomes an open cylinder. It is then quickly withdrawn from the furnace and permitted to depend into the pit beneath the platform. When the plastic edge passes to a cherry heat, the cylinder may be taken away without danger of getting out of shape.

The blower's part is now finished. After a moment's rest, he has another pipe in his hand, and is repeating his heavy labor. His wages are considerably larger than the salary of many a learned professor or divine, but the service for which they are paid is of such a kind that it makes a man grow old very early. The severe muscular exertion, and the high temperature at which it is performed, are not conducive to either health or longevity. There may be exceptions, but as a rule there are few constitutions that can withstand for any length of time the quickly alternating heat and chills to which the glass-blower is daily subject.

The cylinder just laid aside is now cold. As soon as the neck and its attached blow-pipe are separated from it, a red-hot iron is passed along the interior surface from end to end. A piece of cold iron applied to any part of the heated line makes a complete longitudinal crack. We have now before us a perfect cylinder, open at both ends, and cracked from end to end. It has only to be ironed out into a flat sheet to be ready for service as a pane of glass.

The ironing process is carried out in a separate building, in what is known as the laying-in furnace. The ease with which it