76 E. S. Dana — Chondrodite from the Tilly-Foster Iron Mine. 



Table V. 



Angles measured on e- = 2-j (201 and 201). 



Calculated. 



26° 57' 53' 



S 59 19 58 



■( 87 22 38 



j 59 14 



( 82 34 28 



60 30 

 76 32 







14 



j 64 2 9 

 { 69 51 3 



j 44 38 20 



{ 70 20 31 



j 45 45 24 



/ 56 42 18 



37 34 34 

 42 57 12 



26° 55' 



59 14 



44 34 



45 40 



45 50 



YII. 



59° 33' 

 (approx) 



76 26 

 64 



45 46 

 56 42 



IX. 



59° 30' 

 59 30 



76 15 

 63 57 



56 26 



42 43 

 42 32 



26° 51 



59 20 



82 34 



45 42 

 56 42 



42 51 



59° 20' 



76 35 



VI. 

 26° 59' 



XI. 



64° 0' 



negative (or lower) and 7\^ is both + and — , but where occurring 

 alone is generally negative; n'^ is generally, and m^ always, nega- 

 tive. Of the brachydomes it may be said that they are often holohe- 

 dral, but this is not always the case. The various figures on the two 

 plates will show the ti-ue relations better than words. It is to be said, 

 however, that when the brachydomes are ± they are still distinguished 

 from each other physically. Thus the -f- series may be largely devel- 

 oped and rough, destitute of any semblance to polish, when the negative 

 series is as lustrous as the pyramidal planes. When e^ (2-?=:20l) is only 

 once present it is uniformly positive. The macrodomes are always 

 holohedral on humite ; here this is sometimes the case, but there is a 

 good deal of irregularity (as will be seen in the figures), and this is 

 conspicuous in figiire V where i and ik occur together and also e«, ?/?, 

 and i. 



Hahit. — With regard to the general habit of the crystals, it is inter- 

 esting to note the wide variation which is shown. Figui-es 1, 2, 0, 9, 

 10, are intended to give some idea of the crystals as drawn symmet- 

 rically, and figures 7, 10, 14, 15, 16, 17, 18, 19, , of their actual 

 a2:)pearance. As will be seen, the figures are drawn with C(^-^, 010) in 

 front : this was necessary in order to give a true idea of their real 

 appearance. The prism ^-3 is so acute (49^°) that when directed 



