42 Bowles — P yromorphite from British Columbia, Can. 



and on the goniometer give no distinct signals. The bipyramid 

 ?/{2021| was found on three crystals only, and in each case 

 the faces were very indistinct. They are proportionally very 

 much smaller than the faces of the unit bipyramid. The 

 bipyramid ir {4041} was observed with very narrow edges on 

 one crystal only. As no distinct images could be obtained 

 from these faces, several readings were taken, and the results 

 averaged. 



The bipyramid e { 3034} is a new form. It was represented 

 on six of the crystals, and, though the faces are extremely 

 minute, the averages of a large number of readings approxi- 

 mate to the theoretical values so nearly that the form is estab- 

 lished with certainty. The average reading of four of the best 

 faces gives a value 32° 28' for the angle p, the calculated value 

 being 32° 31'. A form having this symbol is recorded for 

 apatite, which also belongs to the hexagonal-bipyramidal class. 

 The bipyramid of the second order, s {1121}, is the only form 

 recorded by Dana or Goldschmidt which finds no representa- 

 tion on these crystals. 



All forms observed by me, as well as those given by Dana, 

 together with their calculated and observed angles, are 

 indicated in the following table : 









Table of 



Angles. 















P 













Forms 



Ob- 





Calcu- 



Ob- 



Calcu 





Dana 



Bowles 



served 





lated 



served 



latec 



c 



{0001} 



{0001} 



0° 09' 





0° 



._ 





m 



{1010} 



jioloj 



90° 03' 





90° 



0° 



0° 







Vicinal 



89° 33' 





.- .. 



0° 



_. 



a 



{1120} 



{1120} 



90° 07' 





90° 



30° 04' 



30° 



X 



{1011} 



{1011} 



40° 37' 





40° 22' 



0° 13' 



0° 



y 



{2021 ^ 



{2021} 



59° 16' 





59° 32' 



0° 13' 



0° 



TT 



{4041} 



{4041} 



74° 07' 





73° 37' 



0° 06' 



0° 



s 



{1121} 





.- __ 





55° 49' 



.- .. 



30° 



e 





{3034} 



32° 28' 





32° 31' 



0° 07' 



0° 



Chemical Analysis. — As extremely pure crystals of both 

 the yellow and green varieties were at hand, it seemed advis- 

 able to make an analysis of each in order to obtain if possible 

 some adequate explanation for the variation in color. The 

 chemical analysis was, in general, based on the method outlined 

 by Medicus.* The results are as follows : 



* Chemische Analyse ; Kurze Anleitung zur Gewichtsanalyse, Dritte 

 Auflage, p. 91, 1897. 



