EYE-PRESERVING GLASS FOR SPECTACLES. 
25 
Table I —Absorption of Heat Rays. 
Glass No. 246 cuts off 98 per cent. 
JJ 
217 
JJ 
96 
JJ 
253 
JJ 
94 
JJ 
240 
JJ 
88 
JJ 
210 
JJ 
87 
JJ 
158 
JJ 
63 
Table II.—Absorption of Ultra-violet Rays. 
Glass No. 240 opaque to rays of shorter wave-length than 3950. 
JJ 
JJ 
JJ 
JJ 
J J 
JJ 
202 
246 
197 
158 
221 
150 
JJ 
JJ 
JJ 
JJ 
JJ 
?J 
JJ 
JJ 
J J 
JJ 
J J 
J J 
JJ 
JJ 
JJ 
JJ 
JJ 
JJ 
3830. 
3800. 
3800. 
3700. 
3685. 
3620. 
Table III. — Transmission of Luminous Rays. 
Glass No. 187 transmits 99 per cent. 
JJ 
251 
JJ 
89 
JJ 
JJ 
250 
JJ 
74 
JJ 
JJ 
150 
J J 
73 
JJ 
JJ 
247 
JJ 
71 
JJ 
JJ 
238 
JJ 
71 
JJ 
Table IY.— -Reduction of Glare. 
Glass No. 
Absorption of 
heat. 
Absorption of 
ultra-violet. 
Transmission of 
light. 
Colour. 
per cent. 
per cent. 
■ 
249 
51 
3550 
63 
Pale blue. 
197 
41 
3800 
45 
Pale neutral. 
252 
47 
3680 
45 
Faint blue-green. 
165 
38 
3680 
42 
Pale yellow-green. 
210 
87 
3620 
30 
Blue-green. 
248 
47 
3550 
30 
Dark neutral. 
E 
12 FEB. 1314 
VOL. CCXIV.—A. 
