THE 
MONTHLY MICROSCOPICAL JOURNAL. 
AUGUST 1, 1869. 
I. — On a Sim;ple Form of Micro-spectroscojpe. 
By John BROwNiNa, F.E.A.S. 
{Bead he/ore the Eoyal Microscopical Society, June 9, 1869.) 
The instrument I have now to describe is substantially tbe same 
in its optical arrangements as that I bad the honour of perfecting 
with Mr. Sorby some time since. As this instrument has been 
described in a paper I gave at the same time to the Society, I shall 
give but a very brief description of it on the present occasion. 
The instrument consists essen- 
tially of a sht A, the width of which 
is adjustable by the screw D. An 
achromatic lens B, which focusses 
on the slit by sliding the tube E in 
the outer tube F F. A compound 
direct -vision prism C containing 
five prisms, and a small reflecting- 
prism P placed outside the slit A. 
This prism is for the purpose of 
throwing a second spectrum into 
the field of view for the purpose of 
comparison. The spectroscope is 
attached to the microscope by the 
adapter G-, which fits into the drawer-tube of the microscope. 
The best method of using this spectroscope is to first find the 
object in the microscope, and bring it to the centre of the field by 
means of an ordinary microscopic eye-piece. Then open the jaws 
of the slit by unscrewing the screw D. Eemove the ordinary eye- 
piece from the microscope, and substitute the spectroscope in its 
place. The object should now show a confused spectrum through 
the jaws of the slit. On closing the slit and focussing carefully by 
means of the sliding-tube E, the absorption bands, if there be any 
in the spectrum, will become plainly visible. 
I have been induced to arrange this simple and economical form 
VOL. II. F 
