338 
Proceedings of Royal Society of Edinburgh. [sess. 
A New Form of Spectrophotometer. By J. R. Milne, 
B.Sc., Carnegie Scholar in Natural Philosophy, Edinburgh 
University. 
(Read July 4, 1904. MS. received August 1, 1904.) 
The present paper is the continuation of a note sent to the 
Society in July of last year,* and is for the purpose of describing 
the developed form of the spectrophotometer whose principle was 
indicated in that communication. 
The former paper described the employment of a divided 
spherical lens to bring together the two slightly separated spectra 
seen in any ordinary form of spectrophotometer. This divided 
lens is placed at about twice its focal length behind the two spectra 
s 
c 
I) 
B 
s' 
produced by the objective of the telescope, and, when suitably 
adjusted, gives rise to two spectra in contact with each other, as 
shown in fig. 1 of the former paper. It has been found, however, 
to be better to modify the action of the divided lens, and to use 
it as indicated in fig. 3. The defect of the former arrangement 
can be seen from fig. l,f where the point b is beneath 0, per- 
mitting light from b to pass straight along beneath the lens-half 
L, to prevent which an opaque stop is required to fill up the space 
00', the stop being so contrived that freedom of relative motion is 
still preserved to the two halves of the lens L and L'. In the 
present arrangement, which is depicted in fig. 3, no such device is 
* Proc. Roy. Soc. Edin., vol. xxiv. p. 496, 1903. 
f See former note. 
