8 DR. THOMAS STEBRY HUNT ON THE 



tance iu this counectiou, and will be considered farther on, in the third part of this 

 paper. 



§ 16. The Huttouians early borrowed the notion of a granitic substratum from 

 Werner, and supposed the earth when lirst cooled to have had a surface of granite. Hvitton, 

 true to his thesis, avoided the question of the primal rock. His reasonings, according to 

 Playfair, "leave no doubt that the strata which now compose our continents are all formed 

 from strata more ancient than themselves," " while, as we have seen, the intruded granites 

 were looked upon as but fused and displaced portions of underlying strata. The granitic 

 character of the rocks which antedated aqueous disintegration was, however, a matter of 

 legitimate inference, and his disciple, Macculloch, supposed the earth when first cooled to 

 have been " a globe of granite." Later, in 1847, ÉJie de Beaumont, starting from the 

 hypothesis of a cooling liquid globe, imagined it " a ball of molten matter, on the surface 

 of which the first granites crystallized." '- 



§ IT. It should here be mentioned that Poulett Scrope, in 1825, put forth what he 

 called "A New Theory of the Earth," iu which he supposes " the mass of the globe, or at 

 least its external zone to a considerable depth, to have been originally (that is at or before 

 the moment in which it assixmed the i^osition it now holds in the jjlauetary system) of a 

 granitic composition, composed probably of the ordinary elements of granite, and having a 

 very large grain ; the regular crystallization having been favored by the circumstances 

 under which it previously took place, though, as to what these circumstances were, I do 

 not venture to hazard a supposition." He farther says, " If then we imagine a general 

 intumescence of an intensely heated bed of granite, forming the original surface of the 

 globe, to have been succeeded by a period in which the predominance was acquired by the 

 repressive force occasioned by the condensation of the waters on its surface, and the depo- 

 sition from them of various arenaceous and sedimental strata (the transition series), the 

 structure of the gneiss-formation is at once simply explained. This structure may have 

 been subsequently increased by the friction of the different laminœ against one another 

 as they were urged forward iu the direction of their plane surfaces, towards the orifice of 

 protrusion, along the expanding granite beneath ; the laminae being elongated, and the 

 crystals forced to arrange themselves in the direction of the movement." This implies an 

 exoplutonic origin of gneiss. 



Later in the same essay, however, Scrope supposes an intensely heated ocean, holding 

 in solution great amounts of silica, and having, at the same time, suspended in its waters, 

 feldspar, qiiartz and mica, derived from the di.'<integration of the underlying granite. 

 These suspended materials were deposited and consolidated into gneiss, and later the 

 dissolved silica, precipitating with some enclosed mica as the ocean cooled, gave rise to 

 mica-schists. In this last, we see the germ of the ther mo chaotic hypothesis, while iu 

 preceding statements of Scrope, we have outlined the early volcanic and metamorphic 

 hypothesis of Dana, to be noticed farther on." 



" Playfair's Biography of James Hutton, in Playfair's complète worlcs, 4 vols, Edinburgh, 1822 ; see vol. iv. 

 pp. 33-81. His Illustrations of the Huttonian Theorj' will there be fourni reprinted in vol. i. 



'- Sur les Emanations Volcaniques et Métallifères. Bull. Soc. Geol. de Fr. (2) iv. 



" Scrope, Considerations on Volcanoes, etc., 1825, pp. 225-228. The cosmogony of Scrope was fantastic in the 

 extreme ; he conjectured the solid granitic earth to have beeri detached from the sun as an irregular mass, and 

 compared it to an aerolite. 



