80 THE SIDEROLITES AND PALLASITES. 



would be very interesting if chemical analyses should be made of the difler- 

 ent portions, in order to ascertain what changes in the ultimate chemical 

 composition have taken place. They should be made from material micro- 

 scopically examined, so that the specific gravity and chemical and miner- 

 alogical characters could be coordinated. The diminished specific gravity of 

 the more highly altered portions of this rock, as above determined, would 

 indicate that considerable changes had taken place in the chemical composi- 

 tion of the rock as a whole. Further, an examination should be made of 

 the least altered portions of this and all similar rocks, for the purpose of 

 ascertaining if they contain any of the elements so commonly found in 

 meteoric pallasites and siderolites. It is not impossible that, on boring, in 

 depth some of the iron might be found in the native state instead of being 

 entirely oxidized. 



Tins rock has been used as an iron ore, for an historical account of which 

 the reader is referred to previous papers of the writer.* 



Tlie additions and changes made in these descriptions to those already 

 published, have been caused by the preparation and examination of other 

 sections, thus making the work more complete. At the time the former 

 descriptions were written, the writer assigned this rock to the peridotites — 

 the most basic olivine rock of terrestrial origin then known. Although its 

 relation to the meteorites was recognized, yet, since the present study of the 

 meteorites themselves was not undertaken until February, 1882, the writer 

 may be pardoned for not earlier perceiving its distinctness from the peri- 

 dotites, properly so called. It is now regarded as a pallasite in which the 

 iron has been oxidized — probably at the time the rock was formed. The 

 writer holds that the rock is eruptive, although no proof beyond its micro- 

 scopic characters has been obtained ; and if its relations to the country rock 

 should be found to be non-eruptive ones, then this view would have to be 

 abandoned. 



If it is necessary to have a distinct name to indicate the pallasites above 

 described, in which the iron is oxidized, tlie writer would propose that of 

 Cumber landite, from the locality in which it occurs in Rhode Island, He 

 would have preferred that of Tuberfjitc, from the earlier described rock from 

 Taberg, Sweden, if that name had not already been in current use in min- 

 eralogy. 



In this direction a vast field exists in the study of iron-bearing rocks 



* Bull. Mus. CoiJij). Zoiil., ISSl, vii. 183-187; Proc. Bost. Soc. Nat. Hist., 18S1, xxi. 195-197. 



