AND TRANSMITTED BY CERTAIN KINDS OF GLASS. 
259 
With 6'5 mm. j^late of Crown Glass. 
Eeadings of analyser. 
Mean.* 
a. 
O 
15 
/ 
0 
o 
40 
38 
0 
39 
07 
50 
53 
138 
30 
139 
05 
138 
47 
48 
47 
222 
0 
223 
45 
222 
52 
47 
08 
319 
30 
320 
20 
319 
55 
49 
55 
Mean 
• • • 
49 
11 
Table IV. gives the values of a determined in this way for the 6‘5 mm., 11'5 mm., 
and 15 mm. plates of crown glass, and the percentage amount of light transmitted, 
as calculated from these numbers. 
Table IV. 
Crown glass. 6'5 mm. plate. 
£ 
Percentnge amount 
Without glass. 
With glass. 
of light tian.smitted. 
47 42 
O < 
49 11 
94-32 
45 44 
49 36 
86-22 
46 16 
48 37 
91-45 
46 54 
48 37 
93-61 
Mean 91-40 
11'5 mm. plate. 
IX, 
Percentage amount 
of light transmitted, ; 
Without glass. 
With glas.s. 
O 1 
O f 
42 03 
44 53 
91-05 
40 14 
43 45 
89-54 
41 16 
44 37 
89-68 
40 09 
42 54 
91-85 
Mean 90-53 ' 
2 L 2 
