Jan. 13, 1888.] 



SCIENTIFIC NEWTS. 



27 



THE NEW CHROMOMICTOR.— I. 



A MOST ingenious and very successful instrument for 

 mixing lights of different colours for experiments 

 in physical optics has been devised by Mr. John Aitken, 

 F.R.S.E., of Darroch, Falkirk. The colours produced are 



(RS, GS, VS) to show the coloured glasses (R, G, V) 

 in the lower circularopening ; and the shutter S is partly 

 removed to show the clear glass opening D. Each shutter 

 is fixed to the end of a long rod (F), mounted horizontally 

 and free to turn on its axis. Only one of the four 

 rods is shown, passing along the side of the box to the 



Sectional View of the Chromomictor. 



very brilliant and beautiful— not of that dull low tone given 

 by the rotation of coloured discs. 



The apparatus is shown in the accompanying figures, 

 and consists of a long wooden box, about 30 inches long 

 by 5 inches deep and 5 inches wide. In one end of the 

 box are two round openings, represented in Fig. i by the 

 spaces D and E, these openings being placed vertically 



other end, where the lever H is attached. Each lever 

 presses on an index I, fixed to the projecting end of the 

 box. By this arrangement the observer can regulate the 

 amount of the different colours which enter the instru- 

 ment while he is looking through the eye-pieces (B), or 1/ 

 one of which is here represented to prevent confusion in 

 the diagram. These two eye-pieces are fitted into the 



Fig. 



End View of the Chrouomictor. 



a short distance apart. The lower opening (E) is about 

 two inches in diameter, and is divided into three equal 

 sectors. Into these divisions are fitted pieces of glass of 

 different colours, to be described in the sequel. The 

 upper opening (D) is a little smaller, and is covered with 

 clear glass. Each sector, as well as the upper opening, is 

 provided with a movable shutter, to regulate the amount 

 of light passing through it. Fig. 2 shows the arrange- 

 ment of these shutters, this being a vertical transverse 

 presentation of the instrument. They are drawn aside 



end of the box opposite the openings, in order that both 

 eyes may be used in the observations. Each of the lenses 

 of the eye-pieces consists of two plano-convex lenses, 

 mounted at one end of a tube, about a foot in length. 

 Each tube slides in a socket (C) fixed in the end of the 

 box. To compare the compound white light with the 

 standard oi white light of the correct brilliancy, a hori- 

 zontal dividing screen (PP) is placed between the two 

 openings (D and E). This screen is fitted horizontally 

 in the box with one end pivotted between the openings, 



