THEORY OP THE EARTH. 43 



But these primitive masses have also suffered 

 other revolutions, posterior to the formation of the 

 secondary strata, and have perhaps given rise to, 

 or at least have partaken of, some portion of the 

 revolutions and changes which these latter strata 

 have experienced. There are actually considera- 

 ble portions of the primitive strata uncovered, al- 

 though placed in lower situations than many of 

 the secondary strata; and we cannot conceive how 

 it should have so happened, unless the primitive 

 strata, in these places, had forced themselves into 

 view, after the formation of those which are se- 

 condary. In some countries, we find numerous and 

 prodigiously large blocks of primitive substances 

 scattered over the surface of the secondary strata, 

 and separated by deep valleys from the peaks or 

 ridges whence these blocks must have been deriv- 

 ed. It is necessary, therefore, either that these 

 blocks must have been thrown into those situations 

 by means of eruptions, or that the valleys, which 

 otherwise must have stopped their course, did not 

 exist at the time of their being transported to their 

 present sites.*f 



Thus we have a collection of facts, a series of 

 epochs anterior to the present time, and of which 

 the successive steps may be ascertained with per- 



* The scientific journeys of Saussure and Deluc give a prodigious 

 number of instances of this nature. 

 f Note D. 



