ON THE GLASS OF POMPEI. 409 



11 These fragments measured no less than ten centimetres, and from my 

 examination of them, all doubt as to the method of their manufacture is 

 removed. The glass had been well melted, except some small knots and 

 other defects ; parts were entirely free from bubbles, while other parts were 

 full of them, but all were not inherent to the melting. The thickness of 

 the glass is unequal ; in some places it is more than five millimetres, and 

 in others not more than three. This alone is a sufficient indication that 

 such glass had not been blown. One of the surfaces of a specimen bears 

 the impress of the form on which it had rested while in the warm state ; 

 this might possibly be the mark of the unmelted portion of the stone on 

 which the cylinder or tubular figure had been developed ; but the other 

 surface bears no resemblance to what would have occurred had the glass 

 been blown, a circumstance also proved by still more positive signs. The 

 bubbles are neither those of a cylinder ncr a globe rolled out into a flat surface. 

 It is clearly seen that each pane has been produced by a running out of the 

 material which, in certain places, did not reach the full size of the mould, 

 while in others, the workman having nearly touched the full size, has turned 

 back by bending the glass upon itself, and by this means the air interposed, 

 forming a stratum of bubbles. The inequality in the thickness, proves also 

 that the workmen made use of no metal cylinders to press the glass." 



It is probable, then, that a metal frame of the dimensions of the glass 

 to be manufactured was placed upon a polished stone over which a small 

 quantity of very fine clay was sprinkled ; the molten material was then 

 poured into the frames probably by the means of ladles of bronze, and the 

 glass was pressed upon by a wooden pallet, so as to fill up the frame com- 

 pletely. The ancients, therefore, came very close upon the invention of 

 molten glass which was only practised in France seventeen centuries after- 

 wards ; for had they passed a roller over the frame, they would have 

 obtained a pane of glass of a regular thickness, which would then have 

 simply required polishing, an operation with which they were acquainted, 

 for Pliny tells us they made use of obsidian for mirrors, which they hung 

 against the walls of their houses, which evidently meant that such obsidian 

 had been polished. 



The glass of these window-panes from Pompei is of a greenish-blue 

 tint, like the common French glass of about fifty years ago. The exact 

 analysis of some specimens made for M. Bontenrps by M. Feed Claudet, 

 gives the following results : — 



Silex . . . . . 69-43 



Lime .... 7 - 24 



Soda . . . . 17-31 



Aluminium .... 3 - 55 



Oxydeofiron . . . .1-15 



„ manganese . . . 0'39 



„ copper .... traces. 



99-07 

 vol. ii. a ii 



