372 PROF. A. FOWLER AND MR. C. C. L. GREGORY ON BAND OF AMMONIA, ETC. 
Description of Plate. 
Fig. I. is enlarged from a photograph of the spectrum of the flame of ammonia fed 
with oxygen ; taken with a small quartz spectrograph. The bright band on the left 
is due to water vapour. 
Fig. II. is from a photograph taken with a quartz spectrograph of moderate 
dispersion, the source being a flame of imperfectly dried cyanogen burning in an 
atmosphere of oxygen. The bright band on the left is due to water vapour. 
Fig. III. shows the band of the ammonia flame as photographed with the large 
quartz spectrograph. 
Fig. IV. is from a photograph taken in the 3rd order of a 10-foot concave grating. 
The short lines at the edges are those of the iron comparisons. The middle spectrum 
is that of the copper arc in ammonia. 
Fig. Y. ( a ) is the solar spectrum, from a photograph by Higgs ; ( b) is the copper 
arc in ammonia, as fig. IV. It is shown as a negative to facilitate comparison with 
the solar absorption lines. Metallic lines are marked by double dots, except in the 
case of iron comparison lines, which are short lines along the middle of the spectrum. 
The scale is that of Rowland. (There is a slight difference of scale of the two 
enlargements, but several lines common to the two spectra are indicated.) 
PRESENTED 
‘ 10JUWJ919 
