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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 distinguishing 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 würde sich vielleicht mit der nächstfolgenden des Diabases vereinigen lassen" (p. 573); and again, in a foot-note to diabase "Wenn der feldspathige Bestandtheil der Gesteine dieser Familie wirklich in allen Fällen Labrador wäre, so würde es zweckmässig 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.