Hunt.] 278 [January 2, 



ferred by Emmons. Portions of this quartzite are thinly bedded 

 and flexible, constituting what is known as itacolumite. It is re- 

 garded by the speaker as identical with the Primal white sandstone 

 of Pennsylvania, which with the Auroral limestone and its inter- 

 stratified and overlying unctuous schists, and the succeeding roofing 

 slates, constitute a distinct geological horizon. This series, having 

 an estimated thickness of about 5,000 feet, is found resting alike on 

 Laurentian, Huronian and Montalban, and is overlaid, probably un- 

 conformablv, by the Upper Taconic, which is the Quebec group of 

 Logan. The Lower Taconic is apparently identical with the lime- 

 stone series of St. John, New Brunswick, which is succeeded by the 

 Menevian slates, and to the Hastings limestones of Ontario, there 

 unconformably overlaid by the Trenton limestones. 1 



This Lower Taconic series, which is very distinct from the wholly 

 uncrystalline Upper Taconic, the speaker distinguishes by the name 

 of Taconian. It is, although in part detrital, essentially crystalline, 

 and its rocks, while distinct from all those of the previously named 

 crystalline groups, have certain lithological resemblances with each 

 of them. The magnesian limestones of the series sometimes contain 

 serpentine, and more often mica, which is frequently finely dissemi- 

 nated, while the associated schists are sometimes in large part made 

 up of a hydrous mica. Crystalline specular and magnetic iron ores 

 are found abundantly in this series, as well as large beds both of 

 carbonate of iron and of pyrites, from the oxydation of the one to 

 the other of which, in place, as has been shown by the speaker, there 

 have been derived the great masses of brown hematite ore, found so 

 abundantly along the outcrop of the Taconian series, from Vermont 

 to Alabama. The stratified clays often enclosing these ores, are the 

 results of the decay of the enclosing crystalline schists, which like 

 still older crystalline strata along the eastern border of the Appala- 

 chian valley, are in many cases decomposed to considerable depths. 



The direct evidences of organic life in the Taconian rocks are 

 certain markings named Scolithus, which are, however, distinct from 

 what has been called by the same name in the Potsdam sandstone of 

 New York and Wisconsin. These, apparently, are found both in the 

 quartzites and the limestones of the series, and the latter moreover 

 contain an obscure and undescribed linguloid shell, and possibly some 

 other organic forms. The question as to whether these rocks are to 



1 Proc. Bost. Soc. Nat. Hist., Vol. xvn, page 509. 



