Mr Poulelt Scrope's Considerations on Volcanos. 359 



supposed to have been originally granitic, and that, on reaching its actual 

 orbit, perhaps before, a great proportion of the pressure was removed 

 which had previously preserved it in a state of crystallization, notwith- 

 standing its intense temperature, (perhaps as an integrant part of the sun, 

 from which the author is inclined to think it a projected fragment,) according 

 to the notion of Buffon and Laplace.* Violent superficial expansion was the 

 result of this diminished compression ; the dilatation decreasing towards 

 the interior, from the surface, which would be completely volatilized to 

 that point where the disaggregation of the granite was wholly checked by 

 the pressure of the zone of liquefied matter gravitating towards it. Where 

 the elastic fluid generated between the crystals of the rock, and which oc- 

 casions its liquefaction, was produced in sufficient abundance, that is, in 

 the outer and highly disintegrated zones, the superior specific gravity of 

 the crystals forced it to rise upwards, and thus a great quantity of aque- 

 ous vapour was urged towards the surface of the globe : as this vapour 

 rose into outer space, its continued rarefaction must have lowered its tem- 

 perature till a part was condensed into water, which fell back in torrents 

 upon the surface of the earth, giving rise to the primeval ocean, which, 

 however intensely heated below, would be retained in a fluid state by the 

 loss of temperature sustained from the vaporization of its surface, and the 

 pressure of the highly condensed atmosphere upon it. This ocean will 

 have contained, both in solution and suspension, the earthy substances 

 which proceeded from the volatilizationof the superficial grarite, or which 

 were carried upwards by the ascending vapour from the disintegrated 

 mass below. The dissolved matters were silex, carbonates and sulphates of 

 lime and magnesia, muriates of soda, and other mineral substances which 

 water at an intense temperature, and under such peculiar circumstances, 

 may be supposed capable of holding in solution. The suspended sub- 

 stances were all the lighter and finer particles of the upper beds where 

 the ebullition had been extreme, but, above all, their mica, which, from 

 the tenuity of its plate-shaped crystals, will have been most readily carried 

 up by the ascending fluid, and will have remained longest in suspension. 

 When the excess of vapour had effected its escape from the disintegrated 

 granite, the crystals of felspar, and those of quartz, which had remained 

 undissolved by the heated water, subsided first, together with the smal- 

 lest and least buoyant crystals of mica; and these crystals would naturally 

 arrange themselves so as to have their longest dimensions parallel to the 

 surface on which they were deposited. This mass, when subsequently 

 consolidated by pressure, formed the gneiss formation, which graduates 

 downwards into granite. Upon this, the larger plates of mica and quartz 

 grains would continue to be deposited, while, at the sann. time, a large 

 quantity of the silex, held in solution by the ocean, was precipitated as 

 the water cooled. Thus was produced, by degrees, the mica-schist forma- 

 tion, graduating downwards into gneiss. On some spots, and perhaps at a 



" The author, in a note, compares the globe at this time to an aerolite, in Which 

 tho superficial crust of vitrified matter bears some analogy to that which then per- 

 haps formed on the surface of our planet.. 



