The leer is a later invention and carries out the same process, only it acts continuously and is in so far an advance. It also consists of a roomy chamber of brick-work, but the fire is permanent and is located at one side of the chamber. A long brick passageway extends for eighty feet from the back of this receiving chamber. The bottles are not piled directly on the floor, but are placed in low sheet-iron cars which move on a track extending the length of the passage-way. As soon as a car is filled, it is moved along the passage-way in order to make room for an empty car in the receiving chamber. In this gradual way the loaded cars are moved along the passage farther and farther from the source of heat, and finally discharge their loads at the cold end of the leer. It takes from forty-eight to sixty hours to accomplish the journey, though this is simply a matter of convenience, as the annealing process itself would not require more than from nine to ten hours, if so long as that.
Ordinarily the bottles, just as they come from the ovens and leers, are ready to be packed and shipped to their purchasers. In case, however, a seal has been blown in the side of the bottle and its prospective contents are of an effervescent character, the strength of each bottle must be carefully tested, as the glass forming the seal is apt to blow out thinner than the rest, and thus be a source of weakness. The testing is carried out by filling the bottle with water and then subjecting it to the pressure of a column of water equal to eighty pounds to the square inch. Only a few of the bottles, however, break under this ordeal.
But in case the bottle has a screw top, as in fruit-jars and the like, or is to have simply a plain ground edge, as in electric-battery jars, it is manufactured with a slight excess of glass on the top. This is known as a "blow-over." In this event the bottle does not pass through the hands of the gaffer, but goes directly from the blower to the ovens or annealing leers. In the grinding department the blow-over is knocked off and the rough edges ground smooth in a rotary grinding machine. In this the bottles or jars are put in upside down, eleven at a time, and have their edges pressed against the face of a large horizontal iron wheel which is rotated by steam-power. The framework in which the jars are held also rotates, and, in addition, each individual jar turns on its own axis. The iron wheel is supplied with a constant stream of sand and water, and this, with the triple motion of the machine, does very effective work. As many as sixty dozen jars can thus be ground in an hour.
The products of such a bottle-factory are as varied as the processes by which they are fabricated. There are large bottles and small bottles, tall bottles and short bottles, thick bottles and thin bottles, ugly bottles and pretty bottles in fine, all sorts of bottles,
