bearing on theoretical Speculations. 191 



could have occurred without creating so violent a disturbance 

 in the level of the then existing sea, as to have caused an im- 

 mense diluvial wave to overwhelm much of the continents 

 previously emerged ? 



Having thus seen that the most elementary phsenomena of 

 geology necessarily involve the existence of such currents, 

 and that therefore they must be by the same necessity ad- 

 mitted in evei-y theory whatever which pretends to account for 

 these phenomena ; let us (as in the former part) proceed to 

 examine the case more in the detail. 



I. The conglomerate rocks and strata of gravel interposed 

 in several of our geological formations indicate several periods 

 of violent diluvial action, of which the last was more recent 

 than the deposition of all our regular strata, and appears to 

 form the precise limit of demarcation between the epochs of 

 the geological formations and the actual epoch ; and in every 

 instance the disposition and distribution of the water-worn 

 materials is such, as to be absolutely incompatible with the 

 theory of their fluvial origin. 



Observations. The British strata which have been most care- 

 fully examined present four principal accumulations of water- 

 worn detritus of preceding rocks, and the Continental series, as 

 far as known, appears to be analogous. These deposits are as- 

 sociated : 1. with the old red sandstone ; 2. with the lower beds 

 of the new red sandstone; 3. with the plastic clay above the 

 chalk ; and 4. they form the most superficial deposit covering 

 all the regular strata. We may examine these in order : 



1. Although we occasionally find beds of a conglomerate 

 texture associated with the grauwacke, yet these appear 

 neither very extensive nor well defined ; it being occasionally 

 difficult to distinguish between true pebbles derived from the 

 fragments of previous rocks, and nodules formed in the settle- 

 ment of a compound mass by the concretion of particular ma- 

 terials round particular centres, through an attraction of 

 aggregation : but in the old red sandstone we often find beds 

 of great extent composed of the conglomeration of indisputable 

 fragments derived from the earlier rocks, and rounded by at- 

 trition. The most common of these pebbles are quartz, derived 

 from the veins of that mineral abounding in all the transition 

 formations. We also find fragments of the harder and more 

 siliceous varieties of slate, jasper, greenstone, &c. It would 

 be interesting to compare more fully than has yet been done, 

 the fragments of this conglomerate with the earlier rocks, and 

 thus to trace them to their original habitats. As to the dis- 

 position of these accumulations of what must have once been 

 gravel, as they form extensive beds, they must have been 



spread 



