Figs. 2 to 7. Instead of relying upon a movement of the optical wedge longitudinally of the axis of the telescope as in Figs. 2 to 7, a pair of wedges W1, W2 suitably 5supported for relative rotational adjustment are mounted between the dispersion prism P2 and the telescope and the dispersion prism P2 is set to project the dispersed beam along the optical axis of the telescope 10instead of below said axis. The wedges W1, W2 are identical in construction so that when they are placed oppositely to each other as shown in Fig. 8, no deviation of the beam will occur, and therefore the central or green 15portion of the spectrum will be visible at the slit S2. When the wedges are in the position shown in Fig. 9, the maximum downward deviation of the beam is secured, while shown in Fig. 10 maximum upward 20deviation is produced. It will thus be obvious that by the rotation of the wedges between the positions shown in Figs. 9 and 10, the beam will be moved transversely or laterally of the optical aperture, thereby 25enabling any portion of the spectriun to be investigated. Any suitable means may be employed for mounting and adjusting the wedges W1, W1, as shown in Fig. 11. I may provide the telescope T with a sleeve 60 30projecting forwardly thereof and terminating in an enlargement or housing 61. Rotatably mounted within said housing are a pair of bevel gears 62, 63 in which the wedges W1, W1 are seated. A bevel pinion 64 mounted 35on one end of a short shaft 65, is interposed between and in mesh with the gears 62, 63 and the outer end of said shaft 65 is provided with a knurled operating handle 66. A pointer 67 and a suitable scale 68 graduated 40in wave lengihs, may obviously he provided for determining, by a direct reading, the wave length of the portion of the beam brought into coincidence with the ocular aperture.
45It will thus be seen that my improved instrument fully meets the requirements hereinbefore enumerated. It will he understood that many changes, variations and modifications of the constructional details of the 50illustrated embodiment may be resorted to without departing from the principles of my invention.
I claim:
1. In an instrument of the character set 55forth, a pair of reflecting surfaces, arranged in spaced parallel relationship, a source of light located between said surfaces, means to vary the distances between said source of light and said surfaces, and an optical prism 60arranged to collect a portion of the light reflected by said surfaces and to direct said light in a pair of substantially parallel juxtaposed beams along a predetermined path.
2. In an instrument of the character set 65forth, a pair of reflecting surfaces, arranged in spaced parallel relationship, a source of light located between said surfaces, means to vary the distances between said source of light and said surfaces, an optical prism arranged to collect a portion of the light 70reflected by said surfaces and to direct said light in a pair of substantially parallel juxtaposed beams along a predetermined path, and indicating means positively fixed and located relatively to aid source of light and75 said reflecting surfaces, said indicating means being constructed and arranged to furnish direct readings indicative of the relative intensities of the light rays incident on said surfaces.80
3. In an instrument of the character set forth, a support, a pair of spaced holders mounted on said support for detachably holding a pair of substances to be compared, a carriage mounted on said support for 85slidable movement between said holders, a source of light mounted on said carriage; and a graduated scale and a pointer, one secured to said carriage and the other to said support, said scale being provided with90 marks to indicate the position of said source of light relatively to said holders.
4. In an instrument of the character set forth; a collimator, a telescope and a dispersion prism secured in fixed relationship to95 each other, said telescope being provided with an ocular slit and means movably supported on said telescope to bring different portions of a dispersed beam of light passed through said prism into coincidence with100 said ocular slit.
5. In an instrument of the character set forth, a support; a collimator, a telescope having a fixed ocular aperture and a dispersion prism secured to said support in105 fixed relationship to each other, and optical means movably supported on said telescope to bring different portions of a dispersed beam of light passed through said prism into coincidence with said ocular aperture.110
6. In an instrument of the character set forth, a dispersion prism, and a telescope fixed against movement relatively to each other, means to direct a beam of light through said prism to said telescope, said115 telescope being provided with an ocular aperture, and means movable relatively to said telescope to bring different portions of the beam dispersed by said prism into coincidence with said aperture.120
7. In an instrument of the character set forth, a dispersion prism and a telescope fixed against movement relatively to each
other, means to direct a beam of light through said prism to said telescope, said125 telescope being provided with a fixed ocular aperture, an optical wedge mounted in said telescope, and means to permit relative movement between said wedge and aperture whereby different portions of the beam 130dis-