504 Prof. Maskelyne and Dr. Lang's Miner alogical Notes. 



1 1 . 2 2 1 = 39 appr. 37 40 calc. 



2 21.221=57,, 59 6 „ 



[221.221][110.TT0] =44 „ 44 37 „ 



[221.lSS][Il0.0Tl] =50 „ 51 6 „ 



The last two angles are angles between edges, and could be mea- 

 sured pretty accurately with the microscope. 



Fig. 2.— 100, 110, 101, 103, 123. 



Fig. 3.— 10 0, 010, 110, 12 3, 3 2 3. 



These forms were observed on small crystals from Medno 

 Roudiansky mine, near Nijni Tagilsk, Ural. They are, with 

 regard to the distinctness of the smaller planes, the best crystals 

 I had for measurement. I found on them the angles 



101.100= 



62 53 



61 



53 calc, 



103.100 = 



98 48 



98 



43 „ 



103.101 = 



36 58 



36 



51 „ 



103.110 = 



96 52 



96 



53 „ 



103(100)103 = 



17 31 



17 



26 H 



123.010 = 



74 54 



75 



8 „ 



123.123= 



29 33 



29 



44 „ 



123.110 = 



87 47 



87 



34 „ 



12 3.110= 



105 48 



105 



68 „ 



323.100= 



66 appr. 



65 



22 „ 



323.^23= 



27 1 



28 



44 „ 



323.110= 



62 „ 



60 



49 „ 



Crystals from a specimen from an unknown locality were similar 

 to fig. 2, only the planes 101 were wanting, and the planes 

 12 3 were more developed. The planes reflected the light very 

 well. I observed 



1 I 3 = 98 49 98 43 calc 

 I 3 123 = 30 appr. 29 44 „ 



The collection of the British Museum contains also specimens 

 from the now exhausted locality at Rheinbreitenbach. But the 

 crystals from this locality, although the largest of all, are not 

 good for measurement, as they penetrate each other very much, 

 and are moreover coated with foreign matter. They seem to be 

 combinations of 1 1 and 12 3, the prism 110 being not 

 much developed, as in fig. 3. 



