128 DE. THOMAS STERRY HUNT ON THE 



dam. It was iu 1846 that he declared the so-called Red Sand-rock of Vermont to belong to 

 the base of the Champlain series, and to overlie the Lower Taconic, but it was not till 

 1855 that this Sand-rock, with its succeeding Graywacke series, was described under the 

 name of Upper Taconic. 



§ 145. These conclusions as to the age of the Red Saud-rock of Vermont were opposed 

 by C B. Adams and by "W. B. Rogers. The former maintained in 1846, after the 

 announcement of Emmons, the opinion that this sand-rock was newer than the Champlain 

 division, and referred it to " the period of the Medina sandstone and the Clinton group," 

 while W. B. Rogers, in 1851, discvissing the same subject, conceived that the reddish 

 limestones which, near Burlington, Vermont, are associated with this sand-rock, were 

 probably " a peculiar development of the upper portion of the Medina group." As regards 

 the relations of this Red Sand-rock and its succeeding limestone to the granular quartz- 

 rock and granular lime-rock of the Lower Taconic, Adams maintained that " the Taconic 

 quartz-rock was probably but a metamorphic equivalent of the Red Sand-rock," and 

 ascribed the change to a supposed "igneous agency." He farther conceived that the 

 granular lime-rock "or Stockbridge limestone of the Taconic system is the eqiiivalent of 

 the calcareous rocks which overlie the Red Sand-rock, rather than that of the lower lime- 

 stones of the Champlain division, as has been commonly sixpposed." Allusion is here made 

 by Adams to the views of Mather and the brothers Rogers, who, as already seen, had 

 supposed this same limestone to be the equivalent of the Calciferous, Chazy and Trenton. 

 This opinion of Adams, which, in 1851, was, as we have shown, supported by W. B. 

 Rogers, was again maintained by the latter in 1860, when, after the reading of an essay 

 by C. H. Hitchcock before the Boston Society of Natural History, Rogers cited from his 

 paper of 1851 the conclusions above mentioned, and announced his opinion, "that there 

 is no foundation for what Mr. Emmons called his Taconic system — a mixture of Silurian 

 and Devonian — and that the Dorset limestone (the Stockbridge limestone of the Lower 

 Taconic) is newer than the Lower Silurian, and probably Upper Silurian or Devonian." ^ 



§ 146. The explanation of this new opinion as to the horizon of the Lower Taconic 

 limestone is made apparent by reference to the Report on the Geology of Vermont, then 

 in process of publication by the Messrs. Hitchcock. Therein Dr. Edward Hitchcock writes, 

 with regard to the limestone in question, then named by him Eolian limestone, and said 

 to be best displayed in Dorset Mountain : " We have found, mostly in strata from below 

 the middle of the limestones, fossils which, though obscure from metamorphism, are 

 clearly referable to genera characteristic of Devonian rocks, viz : Euomphalus, Stromato- 

 pora, Zaphrentis, Chaetetes and encrinal stems." " Nor is it at all improbable, as we shall 

 shortly show, that the Eolian limestone may be as recent as the Carboniferous rocks.^ " 

 Accompanying this will be found a notice of these organic forms as determined by Prof. 

 James Hall, who declared them to be of Upper Silurian and Devonian types. They are 

 compared by Hitchcock to those found to the east of the Green Mountains, in the valley 

 of Lake Memphramagog, the horizon of which is well known. 



§ Hi. We have already noticed the occurrence of outliers of Lower Helderberg lime- 

 stone on St. Helen's Island, near Montreal, and on Belceil Mountain, a few miles farther 



1 Proc. Boston Soc. Nat. History ; vii, 238. 



■' Geology of Vermont, 1861 ; pp. 421 and 418, 419. 



