TABLE OF CONTEXTS. ix 



pehbles had been squeezed or pulled, shown to be only the result of his mis- 

 taking the enclosing matrix foi- the pebbles, 438. Dodgk, in 1881, gives 

 details of his observations near Boston, noticing the occurrence of felsite dikes in 

 the gi-anite, as had been before shown by Wadsworth and Diller, 439. Wads- 

 worth, in 1881, calls attention to more of Crosby's errors of obseivation, 439. 

 "Wadsworth, in 1883, points out the relations of the Roxbury conglomerate to 

 the argillite, 439. Dodge, in 1883, claims that there are two granites in the 

 Quincy district, but offers no evidence in support of this view, 439, 440. 

 Eirors of Shaler, Rogers, and Jackson, in regard to the argillite and granite 

 pointed out by Wadsworth, 440. 



VERMONT AND WESTERN MASSACHUSETTS. 



Small progress made by the earlier investigators toward unravelling the intricate 

 problems presented in this region, 440 ; a specimen from Hitchcock's Final Re- 

 port, 440. H. D. Rogers's division of the rocks below the " Cambrian or Older 

 Silurian " into azoic and hypozoie, 440, 441 ; this classification has no basis of 

 fact, 441 ; he says that it is absolutely impossible to determine " the true base of 

 the Palaeozoic system," 441. Importance to New England that the work of the 

 Canada Survey should be well done, 441. First published statement of the bear- 

 ing of the results of that survey on the solution of problems in New England 

 geology, by Hunt, in 1849, 441, 442 ; the whole of the Green Mountain rocks 

 said by him to belong to the Hudson River group, 441, 442. " With such a key 

 to the structure of the metamorphic rocks of New England, and of the great 

 Appalachian chain," Hunt thinks that "the difficulties that have long environed ' 

 the subject are in a great degree removed, 442 ; similar views expressed by 

 Hunt, in 1850, and Emmons's views of the age of the Taconic entirely rejected, 

 442 ; again, in 1854, Hunt refers the crystalline limestones of New England and 

 their continuation southwest to the Lower Silurian, 442, 443; in 1861, and 

 again in 1863, similar views were expressed, 443 ; in 1866, Hunt said that the 

 Quebec group "constituted the great metalliferous region of Ea.stern Canada, 

 Vermont, and Newfoundland" ; he also refers the cupriferous rocks of Lake 

 Superior to the same group, 443 ; in 1867, he repeated the same statement, con- 

 sidering the Quebec group as being the equivalent of the Landeilo, and further 

 remarkijig that this group formed the Notre Dame and Green Mountains, and 

 that it " played a very important rSle throughout the Appalachian chain," 443 ; 

 this all repeated again later in the same year, 444 ; the statement also repeated 

 that the White ilountains were of Devonian age, 444 ; again, in 1868, it is 

 asserted that there is no proof of the existence in Vermont of any strata older 

 than Potsdam, the gneiss of the Green Mountains being referred to the upper 

 portion of the Quebec group, 444 ; once more, in 1870, Hr.VT asserts the lower 

 Silurian age of the Green Mountains, 445. 



In 1870, Hunt's views undergo metamorphism, and he claims that the theories 

 which he had been advocating since 1863 were only his official ones, and that 

 his own views %vere quite different, 445 ; the rocks of the Green Mountains 

 begin to be called Huronian, the idea of the Devonian age of the ^^^lite Moun- 

 tains being abandoned, and the provisional name of Terranovan introduced for 

 them, 446, 447 ; Dana objects to these views for various reasons, and especially 

 on the ground that minerals are not fossils, and that there is no resison for 



