AMERICA IN GEOLOGY — DECADE OK 1830-1839. 327 



in a highly heated or molten state, whereby was effected a series of 

 changes similar to those known to be caused by* injections of trap into 

 similar strata. 



In his final report Rogers divided the rock formations of the northern 

 division of the State into, first, a group of primary rocks confined to the 

 islands and the vieinit} T of Trenton ; second, a group of older secondary 

 strata confined to the northwestern portions of Sussex and Warren 

 counties, and third, a group of middle secondary strata lying in the 

 broad belt of country between the southeastern foot of the Highlands 

 and the boundary connecting Trenton and New Brunswick. With 

 this third group he also connected the trap rocks of the region. 



The occurrence of graphite in the altered rocks near Sparta, remote 

 from igneous dikes, and its nonoccurrence in more than very trivial 

 quantities adjacent to the dikes, he looked upon as strongly implying 

 that it had been derived '' from the elements of the blue limestone 

 itself, which may easily be proved to contain an adequate quantity of 

 iron and carbon for the production of this mineral." 



The great thickness throughout which this limestone had undergone 

 crystallization, apparently from the heating agency of the dikes which 

 traversed it, and the law which he traced in the development of some 

 of the minerals, afforded, as he felt, unquestionably strong support to 

 the theory that gneiss and other primary strata had once been sedi- 

 mentary rocks, converted by an intense and widespread igneous action 

 into a universally crystalline state. 



The presence of carbonate of copper diffused throughout the fissures 

 of the shales indicated to his mind that a considerable portion of the 

 metalliferous material, particularly the carbonate, had entered the 

 strata in a gaseous or volatile condition and not in that of igneous 

 fusion. The iron and zinc deposits, on the other hand, were ''un- 

 equivocally genuine lodes or veins" filled with "matter injected while 

 in a fused or molten state 11 and not beds formed contemporaneously 

 with the surrounding rock. 



It may be recalled that in 1820 Professor Bakewell visited the Falls 



of Niagara, and on his return to England published in the London 



Magazine a short memoir, in which he endeavored to show that the 



falls were once at Queenstown. In the autumn of 1846 



Rogers's Views on . . . , . 



the Gorge at he again visited the falls and made the additional 



Niagara, 1835. ... 



observation that the river at one time probably flowed 

 through the ancient gravel-filled valley extending from the Whirlpool 

 to St. Davids'. In this subsequent research has shown he was emi- 

 nently correct. Nevertheless, his observations at the time were not 

 wholly accepted. 



In 1834 a Mr. Fairholme, writing in the London and Edinburgh 

 Philosophical Magazine, accepted BakewelTs views as expressed in 



