88 



Schmidt & Haensch, Berlin S. 



3. Landolt-Lippich Apparatus for observing electro-magnetic 

 rotation, with bobbin running on wheels, copper wire solenoid into 

 which is inserted the observation tube. The bobbin runs upon two 

 brass rails and may readily be brought into the optical field. A sup- 

 port for ordinary observation tubes not exceeding 600 mm in length 

 is supplied with the apparatus to render it available for the examination 

 of liquids. Accessories: as under 2. 



III. Apparatus for white or lamp light with wedge 

 compensation and linear scale. 



Equally exact and convenient, but adapted for substances which, like 

 cane sugar, have the same dispersive power as rock crystal; therefore chiefly 

 patronized by sugar refineries and by the custom house, 



a) 1. Soleil-Ventzke's Colour Apparatus 



Fig. 27. 



with adjustment for certain colours in either half of the field, with 

 observation tube of 200 mm and another of 100 mm length, in maho- 

 gany case. (Fig. 27.) 



2. The same apparatus, with tubes of 400, 200 and 

 ICO mm length. 



3. The same apparatus with tubes of 600, 400, 200 and 

 100 mm length. 



b) The same apparatus with double wedge compensation. 

 Original design. 



1. for tubes of 200 mm length, 

 2/ 400 

 3. 600 



(The double wedge compensation with 2 movable rock crystal wedges 

 and scales belonging thereto admits not only of polarization to the left from 

 to 100, but also of easy control of both scales along their entire length, 

 in 1/10%). 



