THE BASIC MASSIVE ROCKS, ETC. 437 



was used to designate those in which hypersthene was supposed 

 to occur. 1 



When Naumann 2 wrote the chapter on rocks for the second 

 edition of his "Lehrbuch der Geognosie" he defined the gabbros 

 as characterized by the possession of labradorite or saussurite 

 and platy augite, and divided them into two varieties — the 

 gabbros, consisting of labradorite or saussurite, diallage and 

 smaragdite, and the hypersthenites, containing hypersthene as 

 the pyroxenic constituent, and sometimes a little secondary 

 hornblende. Naumann recognized the difficulty of distinguish- 

 ing between the gabbros and the diabases, even at this early 

 day, before it was known that augite could have imposed upon 

 it a parting as the result of pressure, for he says " Diese Familie 

 wiirde sich vielleicht mit der nachstfolgenden des Diabases 

 vereinigen lassen" (p. 573); and again, in a foot-note to diabase 

 "Wenn der feldspathige Bestandtheil der Gesteine dieser Familie 

 wirklich in alien Fallen Labrador ware, so wiirde es zweckmassig 

 sein, die Familie des Gabbro mit ihr zu vereinigen" (p. 578). 

 The norites described by Scheerer 3 and Esmark, were thought 

 probably to belong with the gabbros, but their true relations to 

 the group were not known. 



A few years later Kjerulf 4 discussed the results reached by 

 himself and other Norwegian geologists, and ended by dividing 

 the Norwegian rocks of the gabbro type into gabbros and 

 norites, the former consisting of labradorite, augite, hornblende, 

 and the latter of labradorite and diallage. 



j Von Rath: Geognostische Bemerkungen iiber das Berninagebirge (?) in Grau- 

 biindten. lb. IX., 1857, p. 246. 



Rammelsberg : Bemerkungen iiber den Gabbro von der Baste (Radauthal im 

 Harz). lb. XL, 1859, p. 101. 



Von Richthofen : Geognostische Bechreibung von Siid-Tyrol. i860, p. 146. 



2 Lehrbuch der Geognosie. B. I. i860, p. 573-577- 



q Geognostisch - Mineralogische Skizzen, gesammelt auf eines Reise an der Siid - 

 kiiste Norwegens. Neues Jahrb. f. Min., etc., 1862, p. 668. 



4 Zusammenstellung der bisherigen Ergebnisse der geologischen Untersuchung 

 Norwegens. Neues Jahrb. f. Min., etc., 1862, p. 144. 



