On the Manufacture of Glass. 121 



riattening oven, and C, the cooling, or tempering oven. 

 These ovens are prepared for the process, by raising the 

 temperature of the cooUng oven, to about 500° Fah. by 

 means of the flue a, which communicates with a fire place, 

 and grate below. The oven B is raised to the temperature of 

 ignition, through the flue 6, while the rear, communicating 

 with this oven, receives heat from it, but in consequence of 

 the arch covering it being much lower than that thrown over 

 the oven, the heat as you proceed from the oven gradually 

 diminishes so that at its entrance, the temperature is less 

 than that of boiling water. The cylinders of glass being 

 unannealed, it is absolutely necessary to prevent their break- 

 ing, that the heat should be cautiously applied. This is ef- 

 fectually accomplished, by constructing the rear as above 

 described. Within the rear on its bottom are placed two 

 bars of iron extending its whole length, which is usually 

 about ten feet. When the ovens have been brought to the 

 desired temperature, an iron plate is put over the flue at «, 

 closing it entirely; some splinters of wood, are then thrown 

 into the oven, to sustain its heat and give light to the work- 

 men. A boy is now employed, to bring the cylinders and 

 put them in upon the iron bars, in the rear, propelling them 

 successively forward by means of a rod, until the rear is full. 

 A man standing at the opening D, by means of an iron rod, 

 now brings the cylinder which was first put in, upon the 

 stone E ; here the temperature is such, that the glass being 

 flexible, is spread out upon the stone. A block of wood at- 

 tached to another iron rod, is then passed over it, pressing 

 the glass into close contact with the stone. The workman 

 now, with an iron, called the cropper^ shoves it under the 

 partition, upon another stone, F. It is allowed to remain 

 upon this stone, until it is sufficiently cool to retain its form. 

 A man at G, then removes it to the back part of the oven, 

 where he places it upon its edge in nearly a vertical position 

 — thus each successive cylinder is made to pass through these 

 several steps of the process, and they are eventually packed 

 away together in the annealing oven. When the oven has been 

 filled, the fires are put out and every passage into the ovens 

 is closed with mortar. It is allowed to remain in this situa- 

 tion, a week in winter, and ten days in summer; at this time 

 the oven is opened, and the glass being sufficiently cool to be 

 handled without inconvenience, is taken out and carried to the 

 Vol. XVI.— No. 1. 16 



