1076 
PROFESSOR W. N. HARTLEY ON 
That the spectrum remains at its brightest until the end of the “ fining stage,” 
I conclude, from the evidence of my photographs, is certainly not the case. Even 
the eye can detect a waning in the brilliancy of the spectrum. 
See Bessemer photographs 8 and 10, taken at Dowlais; of the six spectra on 
Plate 8 the fifth is by far the strongest. The fourth and sixth are much the same as 
regards manganese, but the sixth is much stronger in iron lines, and also has a 
stronger continuous spectrum. 
On Plate 10 there are nine spectra, each of which received an exposure of half a 
minute, the first and last of these are the weakest. 
In confirmation of this the detailed statement may be Cjuoted which refers to these 
particular plates. 
April 6th, 1893, old Bessemer plant.—Dowlais, grey pig iron, containing not less 
than 2 per cent, of silicon and 3|- to 3f per cent, carbon, was being blown for tin- 
jdate iron in quantities of 10 tons. The position of the instrument was just about 
4 feet above the mouth of the converter and about six feet away from it. The blast 
was turned on at 12 o’clock until 12.5 p.m. ; the flame contained nothing but the con¬ 
tinuous carbonic oxide spectrum, with the usual alkali metals, but at 12.5 p.m. the 
manganese bands began to flash out. The first exposure was at 12.7-g P.M. until 
12 . 8 i P.M. 
h. 
ro. 
s. 
h. 
m. 
s. 
2nd 
exposure from 
. ... 12 
8 
30 
to 
12 
9 
40 
3rd 
' 
, ... 12 
9 
40 
55 
12 
10 
10 
4th 
... 12 
10 
10 
55 
12 
11 
10 
5th 
5 ? ?)•••' 
, ... 12 
11 
10 
55 
12 
14 
10 
6th 
5 5 5 5 • • • • 
, ... 12 
15 
0 
55 
12 
17 
0 
The flame was perfectly transparent at the highest temperatures, and it was 
possilde to look right into the converter and see the fluid slag thrown up against the 
mouth and drop back into the vessel. 
This fact is to be noted, the fourth spectrum had an exposure of exactly a minute, 
while the sixth had two minutes; as regards the manganese bands the spectra are 
much alike, but in carbonic oxide and in iron lines the sixth is much the stronger 
spectrum.. This shows that the quantity of manganese vapour was decreasing, but 
the quantity of iron vapour was increasing. 
Though the fifth spectrum received an exposure half as long again as the sixth, the 
spectrum is much more thau twice as strong. 
