HISTORY OF CRYSTALLINE ROCKS. 13 
arrangement of the constituent elements which, alike by Wernerians and Huttonians, are 
regarded as evidences of deposition from water. This latter or explutonic view was clearly 
expressed by Poulett Scrope, sixty years since, in his “New Theory of the Earth,” published 
in 1825, wherein he imagines the granite to have formed the original surface of the globe, and 
supposes that movements in extruded portions of the mass compressed beneath overlying 
sediments gave to it the gneissic structure. He insists upon the friction of its elements 
“as they were urged forward in the direction of their plane surfaces towards the orifice of 
protrusion, along the expanding granite beneath, the laminæ being elongated and the 
crystals forced to arrange themselves in the direction of the movement.” This view was 
adopted, though without acknowledgement, by J. D. Dana in 1843, when he argued that 
the schistose structure of gneiss and mica-schist is not a satisfactory evidence of sedimen- 
tary origin, since erupted rocks may assume a laminated srrangement.' 
§ 16. The same notion has continued to find favor among geologists of the plutonist 
school up to the present time. Poulett Scrope himself, in rewriting his famous treatise on 
Volcanoes, after a lapse of thirty-seven years, restates his argument with great precision. 
He therein supposes that the primitive material of the globe, so far as known, was an 
aggregate consisting essentially of feldspar, quartz and mica, in a crystalline or granular 
condition. This material, which was impregnated with water and highly heated, possessed 
a certain plasticity, and when extruded by pressure took upon itself a stratiform structure, 
being “ bodily forced up the axial fissure of dislocation in crumpled zigzag folds or upright 
walls of vertical laminated rock.” To show to what extent this view had met the approval 
of other geologists, Scrope farther observed, “The late Mr. Sharpe and Mr. Darwin, as is 
well known, concurred in the opinion here given, that at least as respects the oldest or 
fundamental gneiss, its foliated structure is due not to original sedimentary deposition, 
but to the movement of the particles under great pressure, while the mass was in a con- 
dition of imperfect igneous fluidity. Prof. Naumann has still more recently advocated. the 
same view, which is, however, resisted by Lyell, Murchison, Geikie, and others.” ? 
§ 17. The same view has very recently been brought forward by Joh. Lehmann, who 
maintains, with Scrope, that the schistose structure in crystalline rocks is no evidence of 
aqueous deposition, but is imposed upon them by the process of extrusion. The Saxon 
granulites, according to Lehmann, were intrusive masses, which consolidated among sedi- 
mentary strata far below the surface, and being afterwards forced up by great pressure, took 
upon themselves a banded schistose arrangement, the adjacent strata, more or less impreg- 
nated by the granulitic material, appearing as micaceous gneisses and mica-schists® The 
whole granulitic series of Saxony may be described as made up of fine-grained binary 
gneisses and mica-schists, and has been by the present writer elsewhere referred to the 
younger gneissic or Montalban series of crystalline rocks. * 
§ 18. An example of the resuscitation of the views of Poulett Scrope in North America 


1 Scrope, Considerations on Volcanoes, etc.. 1825, p. 22. See also J. D. Dana, On the Analogies Between Modern 
Igneous Rocks and the so-called Primary Formations, 1843 ; Amer. Jour. Science, 1843, xly. 104-129, and Trans. Roy. 
Soc. Can., Vol. iii. Sec. iii. p. 13. : 
* Scrope on Voleanoes, 2nd ed., 1862, as revised in 1872, pp. 300-365. 
’ Joh. Lehmann: Untersuchungen über die Enstehung der Altkrystallinen Schiefergesteine, 1884. Not hav- 
ing been able to consult this work, I am indebted for a notice of its argument to a review in the Amer. Jour. Science, 
xxxiii. p. 39. * Trans. Roy. Soc. Can., Vol. i. Sec. iv. p. 194. 
