GEOLOGICAL CHANGES. 27 



distinguished from the underlying granite, the adjacent 

 parts of which may sometimes be detected as having been 

 placed there after the deposition of the aqueous rocks. Now 

 the lowest stratified rocks are sometimes found lying in 

 a nearly horizontal position, as they would be originally 

 formed ; but more generally they are tilted up in high in- 

 clinations, with the broken edges directed towards granitic 

 mountains ; indicating that the rise of these mountains from 

 below was the cause of the change of position in the stratified 

 rocks. Thus the earliest strata were in their turn exposed to 

 the wearing influences of sea and atmosphere, and the mate- 

 rials appropriated to form new rocks. And, precisely as 

 might be expected, these new rocks are laid down uncon- 

 formably to the old ; that is, their verges rest at an angle 

 against the sides of the senior formation. These new rocks 

 are again, in their turn, broken up and placed in high inclina- 

 tions by new and similar upbursts of igneous rock ; so as 

 to become liable, of course, to similar disintegration. Such 

 a repetition of wearings down and raisings up, implying fre- 

 quent changes of land and sea, has been in reality the history 

 of our globe since it took its present shape. A granitic crust, 

 containing vast and profound oceans, as is proved by the ex- 

 tent and thickness of the earliest strata, was the infant condi- 

 tion of the earth. Points of unconformableness in the over- 

 lying aqueous rocks, connected with protrusions of granites, 

 and other similar presentments of the internal igneous mass, 

 such as trap and basalt, mark the conclusions of subsequent 

 sections in this grand tale. Dates, such as chronologists 

 never dreamed of compared with which those of Egypt's 

 dynasties are as the latter to a child's reckoning of its birth- 

 days have thus been presented to the now living generation, 

 in connexion with the history of our planet. 



The aqueous rocks, taken in their details, are a vast num- 

 ber. Geologists, however, group them in formations or sys- 

 tems, partly with reference to their lithological characters and 

 the breaks in stratific arrangement above described, and partly 

 with regard to an entirely different class of particulars. It is 

 now time to say that, from an early portion of the sedimen- 



