No. 54025. 



Polarisation Apparatus. Tourmaline Tongs. 



555 



54 621. 1 : 6. 



54 622. 1 : 2. 



54 624. 1 : 5. 



54.618. Microscopic Polarisation Apparatus, Figure (M. P. II, 2, Fig. 802 [II, 1, 763]), 

 with draw tube and lens system, for magnifying the axial images 



The apparatus possesses a very large field of view and permits of viewing simultaneously the 

 poles of the rings in sodium hyposulphite. 



54.619. --idem, Figure, with rack on draw tube and Goniometer for measuring the 



axial angles of the crystals 



54.620. - - idem, with polished mahogany storing box 



With the last three apparatus listed it is possible to observe the axial images and other pheno- 

 mena on crystal plates, gypsum and mica combinations, etc. 



54.621. Large Polarisation Apparatus, Figure, with black mirror, Nicol prism, 3 lenses, 

 preparation holder on one axis, with divided drum, provided with vernier and magnifier 

 for reading off the rotation. The preparation holder can be rotated horizontally and 

 vertically thus rendering possible the focussing of the axial images to a nicety. The 

 apparatus has cross wires which can be adjusted symmetrically narrower and wider 

 by a screw. The apparatus gives a very large and beautiful image 



54.622. Tourmaline Tongs, Figure. Price according to beauty and purity of the tourma- 

 lines (M. P. II, 1, Fig. 680 [654]) 0. 15. 0, 1. 0. 0, 1. 5. .. 



54.623. --idem, Figure, with device for automatically securing the preparations 



(M. P. II, 2, Fig. 799 [II, 1, 758]) 



54.624. Tourmaline Tongs with 6 different preparations, Figure, with box ...... 



Preparations: sugar, amethyst, calc-spar (Iceland), smoky quartz, potassium-cyanide, aragonite. 



54.625. Tourmaline Plates, green, singly Each 0. 6. to 



s. d. 

 0.0 



10. 0.0 



11. 0.0 



15. 0. 

 1.10.0 



1.10.0 

 2.12.0 



0. 10. 



Cl. 321, 1617, 1618, 1621, 

 1619. 1620, 1622. 



