166 THE POPULAR SCIENCE MONTHLY. 



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 con- 

 sists of a roomy chamber of brick-work, but the fire is permanent 

 and is located at one side of the chamber. A long brick passage- 

 way extends for eighty feet from the back of this receiving cham- 

 ber. 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 form- 

 ing 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 bot- 

 tle 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-bat- 

 tery 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 grind- 

 ing 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 pro- 

 cesses 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, 



