254 



Scientific Geology. 



So much of the topography of these rocks, by way of anticipation, 

 seemed necessary in order to explain the peculiar structure of the 

 conglomerate. The layers of the graywacke slate, and amphibolic 

 aggregate run north and south, and dip west, 60° to 70°. And this, 

 as already mentioned, is the direction in which the nodules and schis- 

 tose layers of the cement of the conglomerate are placed. But no 

 strata seams are to be seen corresponding to the dip and direction of 

 the slate. Yet the conglomerate is divided into horizontal layers, 

 from six to ten feet thick ; and also by seams running east and west, 

 perpendicular to the horizon, and parallel to one another, from 10 to 

 20 feet apart. These fissures divide the thick masses of conglomer- 

 ate so perfectly, that they seem as if cut through by the sword of 

 some Titan. The nodules through which the fissure passes, are di- 

 vided very neatly, and the parts present even surfaces, so as to give 

 the rock a quite peculiar aspect. At the southern extremity of the 

 eastern ramification of the range of hills above described, an im- 

 mense quantity of the conglomerate has been carried away by former 

 diluvial action, and the present bluff is terminated by a perpendicular 

 wall, exhibiting this bisection of the nodules in a most striking man- 

 ner. On account of the size, number, and parallel position of these 

 nodules, this singular instance of fracture is much more remarkable 

 than in the variety of conglomerate first described. 



No one can view this phenomenon without enquiring immediately 

 into its cause. And it is obvious at first thought, that this division of 

 , the strata must have taken place since their perfect consolidation : 

 otherwise the nodules, instead of breaking, would have been drawn 

 out of the paste. Nor could mere desiccation have produced such 

 an effect, for the same reason. Nor does any hypothesis afford to my 

 mind the least satisfaction, except that which supposes these fractures 

 to have resulted from a powerful force, acting at right angles to the 

 meridian, beneath the conglomerate, after its consolidation. And 

 when we find large deposites of granite in the vicinity, we have as- 

 certained the existence of a power adequate to such an effect : al- 

 though we might resort to the hypothesis of Elie de Beaumont, 

 which has of late excited so much interest, and which imputes most 

 of the fractures and dislocations of the earth's crust to the secular 

 refrigeration of its internal parts, whereby its outward envelope be- 

 comes too large and partially plicated. 



Another important fact in respect to the conglomerate under con- 

 sideration, is the occurrence in it of numerous veins of quartz. Some 



