Mr Poulett Scrope's Considerations on Volcanos. 357 



rocks, in which such changes, to a certain extent, indisputably take place 

 under similar circumstances, supports this conjecture ; and since all the 

 above varieties of rock are found in nature to graduate into one another, 

 it cannot be unreasonable to suppose all may have been elaborated from 

 the same raw material. 



The work would appear to have terminated naturally here, at least 

 the author is anxious to keep the part of which we have now given a sum- 

 mary, and in which he lias endeavoured to confine himself within the v 

 bounds of strict logical inference, (deducing from the evidence of the vol- 

 canic phenomena, a certain degree of knowledge as to the nature and 

 mode of operation of subterranean caloric, and applying this knowledge 

 to account as well for the detail of these phenomena, as for the inequali- 

 ties in the surface of the globe,) separate from the concluding chapter, 

 which contains theoretical matter of a more general and less substantial 

 character ; in short, an attempt to sketch the outline of what may be called 

 the History of the Globe. 



To this, indeed, the author was naturally led by the results of his pre- 

 vious investigations ; for having proved the existence of a vast subterranean 

 reservoir of caloric, the effect of which is still to occasion violent changes 

 in the superficial crust of the globe, and which appears to have formerly 

 produced similar changes of far greater magnitude, it is impossible not to 

 suppose the same cause to have had a large share in the original formation 

 and disposition of that crust. In fact, the elevating process, which, in the 

 foregoing chapter, is shown to have produced the present irregular dis- 

 position of the superficial rocks, presupposes a peculiar arrangement of 

 these beds, previous to their elevation above the sea level. 



The crust of the globe must then have been composed of concentric 

 coats, consisting of, 1st, The secondary and transition series of strata; 

 'idly, The series of laminar and schistose crystalline rocks, viz. gneiss, 

 mica-talc and chlorite, schists, &c. ; 3dly, and finally, the granitoidal 

 matter, confined at an intense heat by the compression of the overlying 

 strata. 



The origin of the sedimental and arenaceous deposits of the ocean, com- 

 posing the first series, discloses itself by the organic remains contained in 

 them, and their analogy to the actual deposits of our rivers, lakes, and 

 seas. The fragmentary rocks apparently owe the magnitude of the scale 

 on which they have been sometimes produced to the violent oscillatory 

 movements to which, as has been noticed above, the ocean must have been 

 subjected by any paroxysmal elevation of a large portion of its bottom. 

 Even where the elevation took effect only on strata already raised above 

 the sea-level, the effect on the waters of the globe would be still most 

 powerful ; for the radius of the globe being dilated on that point, a propor- 

 tional body of water must rush immediately towards the opposite, or an- 

 tipodal point, to preserve the equilibrium of the globe, and a series of vio- 

 lent oscillatory movements must take place general to the whole ocean, and 

 producing a permanent alteration in the relative levels of land and water 

 all over the earth ; these effects being proportioned to the mass of mat- 



