( 36^ ) 



naiit : y = |011|, well developed and yielding sliarj) reflexes ; )n = SMOj 

 also always present and better retlet'ting- : ir=z\\\'2\, narrow, some- 

 what dull and sometimes wanting altogether. 



In the orthodiagonal zone the forms: |1.0.18|, |J05| and |102| were 

 sometimes met with, in a very rudimentary form. The crystals are 

 elongated along the clino-axis. 

 Anf/uinr vaine.s: 

 c:<l =(001): (Oil)—* 



C: //^ = (001): (110)=* 

 ni: m = (110): (110)=* 

 m-.q =(110): (011) = 

 q:q = (Oil) : (Oil) = 

 C: to = (001): (112) = 

 m-.m =(112): (110) = 

 Probably, a not very distinct cleavage is [)resent along |001|. 

 The substance is optically biaxial ; the exact situation of the axial 

 plane could not, however, be traced microscopically. 



Topical parameters : / : xV -. to = 5,0(^70 : 3,4590 : 10,9290. 



lY. Caksium-salt : CsCOJJCh . HCO,CCl,. 



The analysis 28,90 7» Cs- calculated 28.98 7„. 



Sp. gr. a't 20° C. 2,143; molecular volume 214,18 »/„. 



The salt is very soluble in water. At first, small square plates 

 are deposited; later, on slow evaporation, splendid thicii very lustrous 

 plate-like crystals, which sometimes have a surface of several cm.^ 



It is characteristic, that they may be cleaved as completely as 

 mica, parallel jOOlj. The crystals are represented in fig. 4. 



Caesium-salt. 

 Fig. 4. 



MonocVmic-prismatic, pronounced pseudotelr agonal. 

 a:h:c = 1,0434 : 1 : 0,9706 

 ii = 88°42'. 

 Forms observed: c'^|001|, strongly developed and relleeting ; 



