273 



was found. On jlOlOj occasionally unsymmetrical coiTOsion-figures, 

 like trapezia, are observed. 



Angles: Observed: 



/?:/? =(1101): (1011)=* 76°55' 



f:/?=(0001):(loTl)= 45 59 



c.r = (0001) :(0 ill )= 45 58 



r.s =(0rU):(02"21)= 18 25 



5: m = (0221): (0110)= 25 31 



m:R= (OlTO) : (lOTl) = 68 54V2 



m:t = (OlTO) : (0221) = 25 43 



s:R =:(0221):(10Tl)= 51 14 



r:/? =(10Tl):(0ni)= 42 8 



/?:m = (10Tl):(lÖÏ0)= 44 5 



;r:m = (2241):(10T0)= 40 55., 



x.R = (2241) : (01 IT) = 77 58 



m:x = (OlIO) : (2241) = 40 55V3 



;r:7?=(2241):(10ïl)= 28 2 



x.r =(2241):(0ni)= 28 2 



c.x =(0001): (2241)= 60 48 



( x:x = (2241) : (2241) = 58 24 



Intergrowths of two crystals occur, with their trigonal axes inter- 

 secting under right angles, and one individual rotated about it 

 through ISO''. 



The crystals are distinctly dichroitic : on {1010| for vibrations 

 parallel to the direction of the c-axis, they are orange, for vibrations 

 perpendicular to the first, blood-red. 



Plates parallel to {OOOJ} show in convergent polarised light the 

 interference-image of an uniaxial crystal without circular polarisation : 

 the bars of tiie black cross are regularly extended to the centre of 

 the image. The character of the birefringence is negative for all 

 colours, and it is strong. For iYrt-light is ?io^ 1,6052. 71^ = 1,5804; 

 the birefringence is therefore 0,025. 



When the axial image is very much enlarged, it appears, on closer 

 examination, to be properly biaxial, with an extremely small apparent 

 angle of the axes, and with the axial-plane perpendicular to one of 

 the edges c : r. Although the rotatory power of the crystals is ob- 

 viously very weak, it is, however, rather probable that they represent 

 pseudo-symmetrical intergrow^ths of lamellae of lower symmetry. 



§ 6. III. Laevogykate Potassium-Rhodium-Oxat.ate {^IH^O). 



From the last mother-liquids, in which the more soluble strych- 

 nine-salt is accumulated, the laevogyrate salt, together with some 



