214 ME. W. FAIEBAIEN ACT ME. I. TATE OS THE MECHASICAX PEOPEEIIE3 
scientific research, is very limited ; and often as P 1 obseivations of its 
it is exposed to pressure, few attempts have been made to ^ 
strength. Some researches on the density o s earn testing its powers 
led to an examination of the subject, and a e , nroperties before it could 
of resistance, the immediate necessity of knowing more of its piopeiUes 
be trusted in those expeiimental inquiries. rlpfprtiye that to aiiive at 
Our knowledge of the cohesive properties of glass is so ^ 
satisfactoiy and complete results, it f erushing force, and. 
ment its tenacity, or resistance to a tens e s lai , • . jo an intemal bui-stina 
“ Th J glasrexperimented upon was of three kinds, known commercially as 
Best Flint-glass, 
Common Green Glass, and 
Extra White Crown-glass. 
The flint-glass obtained from Messrs. Molineaux, Webb, and Co., Manchester, was 
ma"d »ide of lead, and carbonate of potash, hi the following proportions.- 
Sand . . . • 
Bed oxide of lead 
Carbonate of potash 
54 per cent. 
22 per cent. 
24 per cent. 
This glass is of a fine transpar-ent character, fusible, mid of a high specific gravity, due 
to the large per-centage of lead in its composition. p ™ Brothers of Bhmiug- 
hal anTrermade of Ld, soda, and lime in the following proportions:- 
Common Green Glass. 
Sand 
Sulphate of soda 
Carbonate of lime 
This is a hard infusible glass of a green 
the flint-glass. 
colour, transparent, but of a less densit) thaa 
