Schmidt & Haensch, Berlin S. 



87 



g) Landolt's Apparatus with Lippich's polarizer. Three 

 modalities. 



The optical equipment is with all three the same. The instruments differ 

 only in the fineness of the divisions on the circles and the necessary means for 

 taking the readings. The first two instruments are intended for determining 

 the rotating powers of fluids, the third instrument can, at the same time, be 

 used for examining electro-magnetic rotation. The instruments consist of two 

 stout brass or iron standards, which are rigidly connected by stout brass rods. 

 Upon these rests a sliding block which may be easily moved horizontally by 

 means of a lever. The sliding block supports the observation tubes. The rigi- 

 dity of the mechanical fittings and the, arrangement of the optical part render 

 the apparatus extremely sensitive. The Laurent polarizer is replaced by a 

 Lippich polarizer. The latter consists of a fixed Glan Nicol which occupies 

 the entire field arid a movable Nicol which fills only one half of the field. By 

 rotation of this latter Nicol the brightness of the penumbra may be regulated. 

 While with Laurent's system only sodium light is applicable the Landolt- 

 Lippich instrument possesses the advantage of admitting of any kind of homo- 

 geneous light being used, 



1. Landolt-Lippich Apparatus with observation tubes of 100, 

 200, 800 and 400 mm length, with large silvered circle divided in 

 1/5 degrees, reading by verniers and simple magnifiers to 0.01 degree. 

 With Landolt lamp for homogeneous light. (Fig. 20.) 



2. Landolt-Lippich Apparatus with observation tubes of 600, 

 500, 400, 300, 200 and 100 mm length. The circle is divided on 

 silver in 400 parts and reads by two microscopes to 0.001 degree. 

 Accessories: Landolt's lamp for homogeneous light and 2 lamps, each 

 with 2 glass rods, for illuminating the divided circle and the micro- 

 scope drums. 



