54 PROCEEDINGS OF SOCIETIES. 
calls it the “Sorby-Browning spectroscope.”’ It is a few inches 
long, contains an eye-piece, and between the two lenses of the 
eye-piece there is an apparatus for adjusting the slit. You can 
adjust the slit in the usual way by a side screw, so as to get any 
amount of opening you like. You can further adjust a vertical 
shutter up or down the slit, so as to reduce the limits of the 
spectrum in that direction. That you can form a little cage in 
which small objects can be optically placed, and isolated from all 
surrounding objects. The prism fits on the top of the eye-piece, 
which carries the slit and other apparatus, and indeed very much 
in the same way in which you can put the analysing prism of a 
polariscope on the top of an ordinary eye-piece. By removing 
the prism or opening the slit you look through the two lenses 
of the apparatus which constitutes an eye-piece, through your 
object-glass, and see the object that you have in the field. You can 
then bring any portion you wish into the centre of the field, and 
adjust the dimensions of the field, if necessary, in two directions, 
and obtain your spectrum either by transmitted light, viewing the 
object as a transparent one, or by reflected light, viewing it as an 
opaque one. There is also a provision for sending a second beam 
light through the prism, it enters on one side, strikes against a 
little right-angled prism, and passes through the slit to the chief 
prism: thus you can easily get two spectra for comparison, at 
the same time, in the field. The general arrangement of the 
apparatus carries out the ideas that were expressed in this place, 
by Mr. Wenham and other gentlemen who have discussed this 
subject. Historically speaking, I believe the matter stands thus: 
To Mr. Sorby belongs the merit of introducing this kind of inves- 
tigation, and he applied it at first exclusively to small quantities 
of fluids contained in cells. Mr. Huggins then sent in a paper 
which was read a meeting or two back, and Mr. Wenham made 
some special remarks on it. That paper and Mr. Wenham’s 
observations called our attention to the importance of obtaining 
the spectra of opaque objects, and to the very curious fact that 
some mineral and other objects yielded mono-chromatic light, 
while others were deficient of the rays they might be expected to 
possess. I saw, and others who are here also saw, a card with 
a small drop of dried blood upon it, and I was told that Mr. 
Sorby had obtained an excellent spectrum from that object. Now, 
in this instrument of Mr. Browning’s these things can be accom- 
plished with very great ease; you take an infinitesimal quantity of 
blood, and you may either view it as an opaque object when dry, 
or as a transparent one, and you can immediately detect its 
characteristic spectrum. Remembering the hint of Mr. Wenham, 
I took a small quantity of fresh blood, and viewed it under Messrs. 
Smith and Beck’s excellent =,th. I isolated a single globule, 
closing the slit horizontally and vertically, so that there was no 
other globule in the field. I immediately got, as Mr. Wenham 
said we should get, a beautifully characteristic spectrum with the 
two distinct dark bands indicating blood. This form of spectro- 
