On the Manufacture of Glass. 119 



thrust down to the bottom of the pot, through the melted 

 glass, when the sudden conversion of the contained water 

 into vapour, creates a motion throughout the whole mass, 

 resembling ebulhtion, raising the glass to the tops of the 

 pots. This soon subsiding, they are next filled with frag- 

 ments of glass, and the cookies again placed in the rings. 



As the fire is continued, large quantities of air in the form 

 of bubbles rise and burst on the surface, until eventually the 

 fluid mass becomes perfectly clear. 



When this fact has been ascertained, the furnace is suflTer- 

 ed to cool down, for one hour or until the glass stiffens on 

 the tops of the pots. During this time the doors of the fur- 

 nace are opened, to clear out of the tone the slag ashes and 

 coal which may have accumulated during the melt. The 

 fire is now gradually increased, until the metal becomes of 

 a proper consistence for blowing. The blowers are then 

 called, and the master stoaker delivers the care of the fur- 

 nace to the master blower, whose duty is to superintend the 

 fire during the blowing. On an average, it takes twenty four 

 hours in melting when the furnace is new, and thirty hours 

 when it has run six months. It is usual to keep one furnace 

 in operation nine months, from September to June, and then 

 to employ the three summer months, in repairing the works. 

 A furnace of ten pots, of the ordinary capacity, will make 

 from seven hundred to one thousand boxes of glass per 

 month, according to the good or bad success attending its 

 operations. 



Blowing. — There is one blower and a boy or apprentice, 

 allotted to each pot. The blower commences by first put- 

 ting the end of his pipe into the ring, leaving it until it is near- 

 ly red, then putting it into the water, when the oxide flies off, 

 and leaves a metallic surface — it is then dipped into the metal, 

 and by turning it around a quantity adheres to it — this is ta- 

 ken out, and if necessary, fashioned by an iron, termed a 

 strike iron, it is again taken to the pot, and by repeated dip- 

 pings a sufficient quantity is accumulated to form a cylinder 

 — this usually requires three gatherings as it is technically 

 termed. The workman now puts the ball of glass a s^hort 

 distance within the ring, where he holds it a few moments, 

 (constantly turning it,) that it may acquire the precise tem- 

 perature necessary. It is then withdrawn, and by means of 

 the strike iron the semi fluid mass is crowded near the end of 

 the pipe, when it is conveyed to a concavity, formed in a 



