„ a™ T TATE 0>- THE MCH.^XICAL PEOPEEIIES 
246 ME. W. ^AIEBAIE^^ AND MB. 
Hence we have the tenacity of glass, 
lbs. per sq. in. 
T=4200, for flint-glass, 
T=4800, for green glass, 
T=6000, for crown-glass. 
and 
The general equation (15.) then becomes- 
lbs. per sq. in. 
P^ 4200 X ;^5 foi’ flint-glass, 
P=4800x|;, 
P= 6000 X ;|5 crown-glass. 
Tor globes of uniform diameter and thickness these formate becomt 
^ IT-- cn in 
lbs. per sq. in. 
P= 16 , 800 x ^5 foi* flint-glass. 
P= 19 , 200 X 5 , for green glass. 
P=24,000Xh crown-glass. 
Besistances of (rlass. 
Mean lbs. per square inch 
Mean tenacity (T.) of glass in the form of thin plates 
=i(4200+4800-t-6000)=5000 lbs. per square uicl , 
.... eooo 
t:_W!»= 2 nearly, 
^^—2560 ^ 
rhat rs, the tenacity of glass in the form of thin plates is about twice that of glass m the 
form of bars. 
Mean resistance (X,) of glass to compression 
= K27582 + 31876+3100S)=30,1601bs. per square inch, 
To 30150 
Ai— =11-8 nearly, 
Tj"" 2560 
that is, the ultimate resistance of glass to a crushing force is about tuel 
resistance to extension. 
