160 THE POPULAR SCIENCE MONTHLY. 



year. Every three hours during the entire twenty-four a charge 

 of a ton and a half of the batch is added to the melting tank. 

 In an atmosphere so intensely heated as this, it does not take very 

 long for the crude materials to fuse and form a glass quite as 

 liquid as water. 



Picture for a moment the white-hot caldron in which this trans- 

 formation of the opaque into the transparent takes place. It is 

 an oblong tank, some eight by ten feet, in which the glass in vari- 

 ous stages of fusion stands to a depth of nearly three feet. Above 

 this seething mass there is a low arch which deflects the long, curl- 

 ing flame as it comes over the bridge from the generators, until it 

 bathes the entire contents of the tank in its Plutonic breath. As 

 the materials of the batch unite and melt alone, they would be 

 for the most part entirely infusible the liquid glass sinks to the 

 bottom of the tank and flows through small openings into the 

 gathering chamber beyond. The glass resulting from the union 

 of sand and alkaline bases is heavier than the crude materials 

 from which it is formed, and consequently seeks the lowest level. 

 In this way the tank, although filled with material in all stages 

 of transformation, has always at the bottom a bath of thoroughly 

 fused glass. The communication between tank and gathering 

 chamber is arranged at such a level that the fluid glass alone can 

 pass from one to the other. 



This central gathering chamber and the busy life surrounding 

 it are the points of chief interest to the visitor who wishes to see 

 the scenic part of bottle-blowing, and is willing to take the chem- 

 istry and some of the more occult parts of the process on faith. 

 The chamber itself is circular, usually about sixteen feet in diam- 

 eter, and contains a bath of molten glass nearly two feet deep. 

 The temperature of this fiery lake is kept above the fusing-point 

 by the hot gases which come from the melting tank and rise into 

 the high shaft immediately over the gathering compartment. It 

 takes only from two and a half to three hours for the crude ma- 

 terials of the batch to pass to the condition of perfectly fused 

 glass. This is pretty quick glass-making. 



A little sand, a little alkali, a little limestone, and considerable 

 heat have so far been expended, and the result is fluid glass. It is 

 that greater amount of skill which is now needed to transform 

 the glass into a bottle. 



There is a series of openings, some sixteen in number, around 

 the sides of the gathering chamber and a little above the level of 

 the molten glass. Through these the glass-blower draws his sup- 

 ply, but he does not dip his blowpipe directly into this glowing 

 reservoir. Such an arrangement would cause too great a loss of 

 heat, besides interrupting the furnace-draught, and would be a 

 source of constant annoyance to the gatherer on account of the 



