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THE BASIC MASSIVE ROCKS, ETC.
435

province, which the writer desires to make as opportunities and time permit. The present plan proposes a series of papers appearing in this Journal at irregular intervals. The first follows this introduction. The second will embrace a sketch of previous work on the basic rocks of the region, and the succeeding ones will treat of the gabbros and coarse diabases in the Huronian and Keweenawan areas on both sides of the lake.

I. BRIEF HISTORY OF THE CLASSIFICATION OF THE GABBROS AND NEARLY RELATED ROCKS.

At about the same time the names Euphotide and Gabbro were applied, respectively by Haüy[1] in France and von Buch[2] in Germany, to rocks composed essentially of a foliated augite and a "compact feldspar." Haüy describes the Euphotides as consisting of a compact feldspar and diallage, for which combination he constructed the name from the two Greek words ἔν (blessed) and φῶς (light), in allusion to the green and white mottling in the hand-specimens from many localities. Von Buch's name, gabbro, was adopted from the Florentines[3] to cover a group of rocks that had been described at various times under a great number of different names, of which perhaps jade was the most common. Although gabbro was used by the Italians to designate what is now known as a diallagic serpentine, it has been accepted by nearly all geologists outside of France as the name to be applied to the group of rocks which von Buch so clearly and definitely separated from other allied rocks, and defined as made up of jade, feldspar and smaragdite.

Between the time of the appearance of von Buch's paper and the publication of the first microscopic description of gabbros by Rose in 1867,[4] many descriptions of these rocks appeared in

  1. ↑ Traité de Mineralogie, 2d Ed., IV., p. 535.
  2. ↑ Ueber den Gabbro, mit einigen Bemerkungen über den Begriff einer Gebirgsart.Geol. natur. f. Freund. zu Berlin, Mag. etc., 1810, IV., p. 128; 1816, VII., p. 234.
  3. ↑ Cf. T. S. Hunt: Contributions to the History of Euphotide and Saussurite.Am. Jour. Sci., 2d Series, Vol. XXVII., 1859, p. 336.
  4. ↑ G. Rose.—Ueber die Gabbroformation von Neurode in Schlesien. Erster Theil.Zeits. d. deuts. Geol. Ges. XIX., 1867, p. 270.
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