180 
PROFESSOR W. N. HARTLEY ON 
Barium Oxide. 
Barium Sulphate. Exposure 30 minutes. 
Ivory scale numbers. 
I 
24-5 to 
17483 
5720 
17508 mean 
5712 
25 
17551 
5697 
25-.3 to 
17575 
5690 
26‘1 continues to 
17667 
5660 
27-2 
17795 
5619-5 
28’0 to 
17900 
5587 
28'9 continues to 
18002 
5555 
30-5 
18183 
5499 
29-3 
18037 
5544 
30-5 
18170 
5503 
34'0 to 
18572 
5384 
35-0 
18670 
5356 
36‘0 to 
18789 
5322 
39-5 
19154 
5221 
41'5 to 
19373 
5162 
44-0 
19648 
5089-5 
50 to about 
54 
20275 
4932 
51"8 to 
20463 
4887 
52-8 
20565 
4862-5 
54-0 
20690 
4833 
59 to 
21208 
4715 
60 
21312 
4692 
J 
Remai'ks. 
The centre of a weak band. 
A strong band overlapping a weak 
one. 
A band wbicb is weakened between 
28'9 and 30'9. 
A line lies on the preceding P.s. 
band. 
End of baud, shai’p. 
End of band, sbai’p. 
End of band, sharp. 
Band. 
Stronger part of band. 
Very faint band. 
