130 Mr. J. E. Reynolds on a modified Spectroscope 



control; hence I set to work to remedy the defect above referred 

 to, and have succeeded in arranging the spectroscope so as to 

 admit of its use in ordinary analysis with great facility and com- 

 fort to the operator. 



The accompanying woodcut represents the spectroscope as seen 

 from above. 



A is a circular table of 

 brass surmounting a pillar 

 and heavy foot, not shown in 

 the drawing. In the centre 

 of the table and on a raised 

 metal disk the prism B is 

 fixed securely, but the small 

 carrier-plate admits of slight 

 rotation round its centre in 

 order that the adjustment of 

 the prism may be easily ef- 

 fected ; the latter is a glass 

 cell filled with bisulphide of 

 carbon, the refracting angle 

 being 59°. The tube D is 

 fitted to the table, and carries 

 at one end the slit S and ad- 

 justing- screw, and at the other 



the collimating lens. On a little stage is fixed the reflecting 

 prism g, the use of which will presently be shown. T is the 

 observing-telescope, which has a magnifying-power of about 6; 

 this tube is carried by a stout arm, which latter permits consi- 

 derable angular motion of the telescope. K is a short tube, also 

 moveable round the centre of the table ; at one end of the tube 

 is placed a photographed scale, and at the other a lens, with the 

 scale in its principal focus. 



In using this instrument, light from any source, after passing 

 through the slit S and the plano-convex lens, instead of being 

 allowed to fall directly on the first face of B, as in the ordinary 

 instrument, is reflected at a right angle to its first path by means 

 of the little prism g, and then passes through the prism B, suf- 

 fering refraetion and dispersion ; the spectrum so produced is 

 then observed with the telescope T. In accurate experiments, 

 of course, it is necessary to measure the distances which inter- 

 vene between the lines produced by any flame under examination : 

 this is easily effected by adjusting the tube K ; and when a candle 

 is placed behind the photographed scale, a bright image of the 

 latter is thrown into the telescope T by reflection from the second 

 face of B. When in use, the instrument is covered with a japanned 

 tin cap blackened inside, with slits cut in the sides to admit of 



