spectrography (spektrografi)

[As spectrograph +-y3.] The art of using the spectrograph. spectrological (spek-tro-loj'i-kal), a. [ branch of science which determines the constituent elements and other conditions of bodies by examination of their spectra. spectrometer (spek-trom'e-ter), n. [ beam; (2) the prism P, which can be turned upon the cen IMG:content-1680.png:[blocks in formation] tral axis, its position being centered by two slides moved at right angles to each other by means of the screws E and E'; (3) the observing telescope A, the eyepiece of which is provided with cro -wires so that the position of a given line can be accurately fixed; the axis of the telescope can be made horizontal by the screw N. After the position of the prism has been accurately adjusted, usually so as to give the minimum deviation for the given ray, the angle of deviation is measured by the telescope moving with the graduating circle C, while the prism (with the vernier) is stationary. By the tangent screws at O and O the positions of the two circles can be adjusted more delicately. The instrument can also be used, like the ordinary reflecting goniometer (it is then a spectrometer-goniometer), to mea spectroscope sure the angle between the two faces of the prism which angle, with that of the minimum deviation, is needed to give the data for calculating the required refractive index. (See refraction.) If a diffraction-grating instead of a prism is employed, the telescope A is moved into the position A', making a small angle with the tube B; the instrument may then be used to measure the wave-length of a given light-ray.