6o8 



THE POPULAR SCIENCE MONTHLY. 



until a large bubble of air is formed in the midst of the mass ; 

 then, with alternate blowing and manipulating, he so increases 

 the size of the bubble that the ball of glass assumes a shape not 

 unlike that of the large carboys used in the transportation of 



Casting Plate Glass. 



acids. He now transfers himself and his work to the platform in 

 front of the furnace. Sometimes blowing, sometimes swinging 

 his pipe in the pit beneath him, and sometimes reheating the glass 

 in the blowing furnace in front of him, the blower gradually ex- 

 tends the dimensions of the bubble of air until the ungainly car- 



