164 



NEW YORK STATE MUSEUM 



tions were given by extremely narrow faces and the images of the 

 signal although distinct were very weak. The average of the four 

 readings which identified the form is as follows : 



Letter 



Symbol 



Measured 



Calculated 



6:2, . .■ 



910:510 



8o° 31' 



8o° 44' 





F (380). This new prism was observed on only one of the series 

 of crystals measured. The reading from a narrow but sharply 

 defined plane gave: 



Letter 



Symbol 



Measured 



Calculated 



b:F 



010:380 



24 46' 



24 42' 





X 5 (215). This new pyramid was observed on one crystal of the 

 series measured. The observed plane, although, small, was sharp and 

 well defined, yielding measurements in two zones, which admit of 

 xts identification by zone equations as well as by the measured angles. 

 It was identified by the following observations : 



Zone 



po 1 : 102 j 

 1001:210] 



Angle 



011:215 

 001:215 



Measured 



47° 45' 

 34 57 



Calculated 



48 2' 

 34 505 



A crystal of type 3 is shown in figure 7. The same crystal which 

 furnished readings on the new pyramid (215), yielded a faint and 

 somewhat obscure reflection in the zone [on : 102] which corresponded 

 to the hitherto unrecorded pyramid (5.1. n) as follows: 



Letter 



Measured 



Calculated 

 (5-i.ii) 



d:? 



56° 56' 



55° 45' 







The form must be considered of doubtful establishment. 



