6 Field Columbian Museum — Geology, Vol. III. 



however, is considerably stouter in habit than that in Bella Roca. 

 The chief point of difference between the two irons, however, and 

 one which in the writer's view seems alone to warrant their separa- 

 tion, is that in Rodeo there is an entire lack of the inclusions of 

 troilite which form so striking and important a feature of the compo- 

 sition of Bella Roca. Although eight full-sized sections have been 

 made of Rodeo, no troilite has as yet been observed in it. In Bella 

 Roca, however, as is well known, troilite is an abundant and charac- 

 teristic constituent. The chemical analyses of the meteorites do not 

 show important differences, but this would not be expected as between 

 medium and fine octahedrites. Still the analyses show a relative 

 absence of sulphur and hence of troilite, and abundance of phos- 

 phorus and hence of schreibersite in Rodeo, while the opposite condi- 

 tion holds in Bella Roca. The analyses compare as follows, that of 

 Bella Roca being by Whitfield:* 



Fe Ni Co Cu P S C 



Bella Roca. . 91.48 7.92 0.22 0.21 0.21 0.06 = 100.10 



Rodeo 89.84 8.79 0.28 0.07 0.80 0.02 0.09 = 99.89 



In view, therefore, of the distance between the localities and the 

 difference in structure and composition, there seems to be sufficient 

 reason for regarding Rodeo as a distinct fall. 



*Am. Jour. Sci. 3, 37, p. 439. 



