118 On the Manvfacture of Glass. 



The furnace is supported at the four corners, by pillars of 

 masonry and upon each of these it is usual to build a cal- 

 cining oven, with a flue communicating with the furnace. 

 This arrangement saves the expense of the fuel which would 

 be otherwise consumed in preparing the materials. 



When a furnace is built it requires from three weeks to a 

 month, to raise the temperature, to the desired degree, after 

 which the heat is sustained steadily and uniformly in the fol- 

 lowing manner. The stoaker, as the fireman is called, com- 

 mences his tour of duty by taking two sticks of dry wood, 

 he puts one of them into the hole in the clay door near hun, 

 then walks deliberately around the furnace, to the further 

 door where he deposits the other in the same manner ; con- 

 tinuing his travels, he encircles the furnace, and again sup- 

 plies himself with wood. Thus moving at the rate of about 

 three miles an hour, he continues his route supplying regular- 

 ly the furnace with fuel, until he is relieved at the end of six 

 hours, by another stoaker, who is likewise relieved by the first. 

 We usually employ, and always prefer for this business su- 

 perannuated blowers, as they are familiar with the manner 

 in which the fire should be regulated, so as to produce the 

 quickest melt, with the least quantity of fuel. Although 

 it appears a very simple operation, yet two hours of time 

 will be gained in every melt, by employing an experienced 

 stoaker. 



Melting. — When the furnace has arrived at what is cal- 

 led a white heat, the vitrifiable materials, (or mixing,) are 

 thrown into the pots through the rings, by means of an iron 

 shovel made for the purpose. After the pots are filled, the 

 cookies are replaced, and the fire increased to its max- 

 imum, and regularly continued, until the materials are per- 

 fectly fused, during which operation, the superintendant of 

 the furnace or master stoaker as he is termed, occasionally 

 examines the glass with an iron rod, to ascertain the state 

 of the melt, and that it is going on prosperously. The fu- 

 sion of the first laying in being accomplished, the pots are 

 again filled with mixing — and this process is repeated, until 

 the melted metal, is within three inches of the top of the 

 pot. To insure an intimate mixture of the different layers 

 of glass, and form a perfectly homogeneous mass ; it is now 

 stirred. 



This is done either by means of a billet of wood or what 

 is better a potatoe put on the end of an iron rod. This is 



