74 



Franz Schmidt & Haensch. Berlin S. 



c) Large size. Magnification of the telescopes 10 or more. Slit 

 with reflecting prism. The circle of 170 mm diameter is divided in l / Q 

 degrees on silver, reads to 10 seconds and is protected from dust by a 

 brass hood. 



These sizes are, on account of their stability, specially adapted for 

 automatic connections with several prisms, also for equipment with polar- 

 izing apparatus and Babinet's compensator, crystal movement and so 

 forth. The usual collimator may be easily replaced by Kundt's collimator, 

 which is specially adapted for photometric purposes; the latter is fitted 

 with micrometer screw and bilateral slit with helioscopic objective. The 

 latter can be gradually closed by segments. 



T. Spectrum Apparatus, for special scientific and technical 



purposes. 



a) Spectrum-Photometer according to von Vierordt for photo- 

 metry or qualitative and quantitative chemical spectrum analysis, with 2 

 telescopes; the observing telescope is fitted with rack and pinion and 

 ocular slit, the collimator tube with double slit, divided drum and reflecting 

 prism. Large and small model. 



b) Spectrum-Photometer according to Glan with reversion of 

 the Nicol prism. 



H 



Fig. 10. 



vid. 



One of the most popular apparatus. (Fig. 10.) (For particulars 

 Poggendorfs Ann., 1877. - - Vogel, ,,Das Spektroskop."} 



c) Spectrum-Photometer according to A. Koenig. 



d) Ophthalmo-Spectroscope, simple and composite, for testing 

 colour blindness, according to vonVierordt's andHolmgren's suggestions. 



