Schmidt & Haensch, Berlin S. 85 



The sleeve is adapted both for a short tube intended to take 

 low power lenses and for a long tube fitted with worm screw intended 

 for higher powers, apochromatic lenses in conjunction with projection 

 oculars. (Fig. 23.) 



d) Projection head, for projecting photographs and objects in 

 general by means of photographic lenses. The focus of these lenses 

 must, of course, be adapted to the focus of the illuminating lens of 

 the Camera. We must here refer to the Separate Catalogue on ^Optical 

 Benches'', n-h'n-h may be had from tlte firm's representative. 



D. Polarizing Appliances. 



Beside the well knowD instruments of Mitscherlich, Laurent, Wild, 

 Xandolt-Lippich, Soleil-Yentzke's colour apparatus and Jelett-Cornu's pen- 

 umbra apparatus, the firm makes also new appliances for observing electric 

 and magnetic rotation, for polari-spectro- photometric research etc. These in- 

 struments are all of the most approved form and perfect workmanship, both 

 as regards the optical and mechanical parts. 



I. Appliances for didactic purposes. 



a) Dove's apparatus for demonstrating polarization pheno- 

 mena, consisting of a divided prismatic beam with sliding pieces 

 provided with brass standards for the accessories, with open telescope 

 fitted with divided circle, with Nicols, condensers etc. 



b) Noerremberg's Apparatus with accessories. 



c) Wild's, Laurent's apparatus and others, vid. II. 



d) Arago's, Babinet's, Savart's, Senarmont's polariscopes. 

 (vid. also under heading ,, Optical benches' 4 .) 



II. Apparatus for analytical purposes, for homogeneous light, 

 with divided circular disc. 



a) Mitscherlich's apparatus; simplest form with two Nicols, 

 1 lens and 1 observation tube 200 mm long," on stand. 



b) Robiquet's apparatus.; equipment similar to that of a, but 

 with the addition of a double rock crystal plate. 



c) Wild's apparatus, large model, on adjustable brass stand, 

 with interposed Savart plate, with circle divided on silver, telescopic 

 reading, with observation tubes of 220, 200 and 100 mm length and 

 with sodium gas lamp ; the whole apparatus fitted in a mahogany box. 



d) Wild's apparatus, small model, with observation tube of 

 100 mm length. 



(These Wild instruments are very sensitive, but are not suitable for long 

 continued working owing to the eye being severely strained by their use.) 



