AMERICAN GEOLOGY EATONTAN ERA, 1820-1829. 289 



the trap —a recognition here of the value of fossils for stratigraphic 

 purposes. 



The clay-slate of the South Mountains he regarded as belonging to 

 the transition class, since it dips .50 or 60 to the northwest, while 

 the sandstone dips at an angle of only lo or 15° to the north, clearly 

 indicating the former rock to be of greater antiquity than the latter. 

 Moreover the slate contained only marine fossils. It was regarded 

 also as having existed before the neighboring plutonic rocks had 

 emerged from the central region of the earth. 



The granite was regarded as being undoubtedly of greater age than 

 the clay-slate, since it contained '"no relics of organized beings." He 

 did not, however, consider it as belonging to the oldest primitive 

 rocks, since it showed at places a brecciated structure, contained black 

 mica, and was "lacking in the metalliferous compounds and minerals 

 which characterize the ancient formations." "It probably belongs," 

 he wrote, '"to the third or newest formation of Werner." 



Concerning the source of the trap and its relationship to the sand- 

 stone, he wrote: 



The sharp fragments of the breccia and the breaking up of the strata also shew 

 that the production of this rock or, rather, its nonconformable position on the sand- 

 stone strata, was effected suddenly. Whether it was ejected from the inaccessible 

 depths of the Basin of Minas, or was thrown directly up through the strata of sand- 

 stone, we can not determine; but the occurrence of the trap only on the borders of 

 the basin, which it almost surrounds, leads to the belief that this cavity was the 

 crater, if it may be so called, from which, in former times, the trap rocks issued. 

 The same remarks will apply to the whole North Mountain range, except that they 

 probably originated from the unfathomable deeps of the Bay of Fundy, which is 

 completely skirted on either side by trap rocks. 



It will be noted here that Jackson for the first time cut loose from 

 the Wernerian (Neptunian) doctrine. He realized this and stated that 

 the evidence found convinced him of its insufficiency, and he was 

 obliged to allow the superiority of the igneous theory as taught b} T 

 Hutton, Play fair, and Daubenv. 



Writing of the origin of the bed of hematite iron ore of the South 

 Mountain region and its relation to the granites, he said: 



Speculative geologists would doubtless regard the protrusion of the granite from 

 the central regions of our globe as the cause of the disruption of the strata of clay- 

 slate which was thus raised from the bottom of the sea, bearing with it the spoils 

 of the ocean. The layers would thus be broken, their edges thrown up at an angle, 

 and, by the contraction of the subordinate rocks, the superior strata being fixed, 

 or the protrusion having carried the rocks so far as to poise the strata in a per- 

 pendicular position, a chasm would be formed into which the ore of iron was after- 

 wards poured from above by a second submergence. From the similarity of fossils 

 we should think the bed of iron ore must have been immediately formed after the 

 disruption of the strata, 



In 183)-) a revised edition of the work was published in the Memoirs 

 of the American Academy of Arts and Sciences. This was referred to 



NAT MLS 1904 19 



