108 Proceedings of Roycd Society of Edinburgh. [jan. 6, 
1 1 
4 dc^ 4c dc ah - 
pTq Id 1 ' 
2 dc ab- 
1 
2PQc 
-(P + Q)(a6-c2). 
5. On some Glass Globes with Internal Cavities produced 
during Cooling. By J. T. Bottomley. 
the Royal Society a number of flint-glass globes having remarkable 
internal cavities produced during cooling. Along with these globes 
there is exhibited for comparison one globe having no perceptible 
internal cavity. 
The making of these globes was shown to me by Mr John Griffin, 
manager of the St Eollox Flint Glass Works, Glasgow. 
The globe having no internal cavity is marked A. A set of globes, 
four in number, are marked B^, B 2 , Bg, B^, and the sixth globe is 
marked C. 
The globes which have cavities were formed in the following 
way : — A pot of the finest glass having been selected, very free from 
any appearance of scum or bubbles, a ball of glass was gathered in 
the usual way at the end of the glass-blowers’ iron or long blowing 
tube, and it was worked with the help of a wooden mould into the 
form of a glass ball projecting out, by a short neck of glass, from 
the end of the iron. When the red hot ball had been thoroughly 
examined to see that there was no flaw of any kind in the mass, 
the operator quickly brought it to the open window, and held it in 
the draught which was blowing sharply into the glass-house. The 
ball was at this time very bright red hot — glowing, in fact — and it 
was quietly turned round and round in this cold position, so as to 
cool equally all round. 
At first it looked perfectly uniform throughout, but soon there 
{Abstract.) 
The object of this communication is to exhibit and describe to 
