1896.] NEW YORK ACADEMY OF SCIENCES. 47 



To accomplish tlie simultaneous rotation the tube nicol N is 

 thrown out and a cap nicol J^ is used as an analyzer which can 

 be thrown in and out just as with the tube analyzer iV and can 

 be clamped in any desired position by the small screw d. The 

 •cap nicol A^, and the polarizer A are made to rotate, always re- 

 taining the same relative position, by the cogwheels r^, Z^ and 

 r, Z respectively, these being connected by the rods S and S^ of 

 which the latter slides in the former with anj' raising or lower- 

 ing of the tube. The upper toothed wheel Z^ carries a graduated 

 circle which can be read to five minutes b}' a vernier. 



During ordinary manipulation with the tube analyzer, JV, the 

 toothed wheel combination is clamped b^- the screw, B, the 

 vernier of Z^ being at 0°. The field of sight is then as large as 

 with the No. 1 model, but when the cap analyzer is used the 

 field is somewhat smaller, though just as distinct. 



The exact adjustment of the polarizer and cap anal3'zer is 

 best made by use of a stauroscopic ocular, both have microm- 

 eter screws, A and A^ for fine adjustment. 



The tube analyzer can be turned 90° and the rotation read 

 upon a quadrant not shown in the drawing. 



The Bertrand lens, /, which is used with the No. 2 ocular can 

 be separately focussed and has beneath it an irisblende by clos- 

 ing which very small sections can be separated from disturbing 

 surroundings and the axial image made sharper. 



II. The Universal Rotation Apparatus of Prof. Klein.* 



This apparatus, shown in Fig. 2, must be used with a micro- 

 scope possessing an adjustable stage and a stand which permits 

 a, horizontal position of the microscope. It is especially adapted 

 to the large No. VI. Fuess Microscope just described. A special 

 condensing lens and objective are furnished with the apparatus. 



With the microscope in horizontal position, the plate, G, is 

 strongly clamped to the adjustable stage, which has iJreviousl3' 

 been turned so that one of the adjustments is horizontal, the 

 other vertical. The carrier, T, attached at right angles to G, sup- 

 ports the apparatus, with the axis, P, in vertical position. P is 

 clamped to the disk, K, by F, and carries below a centering de- 

 vice consisting of two quadrant arcs, L and Lj, which are at 

 right angles and have their common centre just beyond the crys- 

 tal carrier, F. The arcs are moved and clamped hy the screws, 

 IF and B, and by verniers can be read to five minutes. The crys- 

 tal is attached b}' wax kneaded with soot, and new wax is used 

 each time. 



*C. Klein. Sitzunc/sber. cler Acad, der Wissenschafteh. Berlin, 1895, p. 91. "Der 

 Universaldrehapiiarat," etc. 



