ULTEA-BASIC INTRUSIVES. 



219 



these porphyries, in whicli, by the w?ij, the iron content is relatively low, 

 is unique, in that it is very strongly polar magnetic, and in this, as well as 

 its probable original mineralogical composition, may be compared with the 

 polar magnetic wehrlite from the Frankenstein, Hesse-Darinstadt, Germany.^ 

 The Gi-erman rock shows tremolite scattered through the serpentine result- 

 ing from the olivine. It is a coarse, evenly granular rock, differing in this 

 respect from the Crystal Falls rocks which are porphyritic. 



An analysis (No. 1)' of the polar magnetic serpentinized picrite- 

 porphyry, in Avhich great abundance of olivine was originally present, is 

 here given, and there is placed with it for comparison an analysis (No. 2) 

 of a very similar rock described by Darton and Kemp," from New York. 

 Both analyses were made by Dr. H. N. Stokes, United States Greological 

 Survey. In No. 1 Ba, Sr, Li, CI, 'S, and SO^ were not looked for. 

 Analyses of picrite-porpliyry. 



' Der raagnetstein von Frankenstein an der Bergstrasse, by Audreae und Konig: Abhandl. der 

 Seukenberg. naturf. Gesell., Frankfort a Main, 1888, pp. 59-79. 



Cf. Above article, p. 66, footnote, for references to other occurrences of tremolite associated 

 with serpentine. 



-Newly discovered dike at Dewitt, near Syracuse, New York, by N. H. Darton and J. F. Kemp: 

 Am. Jour. Sei., Vol. XLIX, 1895, p. 461. 



