Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . ^a; Fig. 273 shows the Fuess goniometer * (Model 4, a) which isadmirably adapted for student work. It is very much lower pricedthan the Model 2, but is exceedingly simple in adjustments andaccurate in its results. * R. Fuess, Steglitz, near Berlin, marks 260, or about 65 dollars. 74 CRYSTALLOGRAPHY. Two -telescopes are used : (a) The collimator telescope C fixed in a constant position anddesigned simply to guide to the crystal a ray of light from a lampset at the outer end. At this end is an orifice
Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . ^a; Fig. 273 shows the Fuess goniometer * (Model 4, a) which isadmirably adapted for student work. It is very much lower pricedthan the Model 2, but is exceedingly simple in adjustments andaccurate in its results. * R. Fuess, Steglitz, near Berlin, marks 260, or about 65 dollars. 74 CRYSTALLOGRAPHY. Two -telescopes are used : (a) The collimator telescope C fixed in a constant position anddesigned simply to guide to the crystal a ray of light from a lampset at the outer end. At this end is an orifice like a double crescent,Fig. 274, formed by two circular discs of equal diameter set a dis-tance apart which can be regulated by a screw. {b) The observation telescope T, which may be set at any de-sired angle to C, though the axes of T and C always remain in ahorizontal plane and intersect in the axis of rotation. Within Tare two cross hairs, one vertical, the other horizontal, adjusted tointersect in the axis of the telescope. The vertical cross hair isparallel to the axis of rotation. Be
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