142 GEOLOGY OF THE SECOND DISTRICT. 



which resulted sometimes in the complete overturning of the strata. At present, I am dis- 

 posed to regard the matter in a more simple point of view, viz. as nothing more than uplifts, 

 which, in consequence of the confined position of the rocks, have often produced local fold- 

 ings or plications of the strata. These foldings appear mostly in the valleys. 



Liability to mistake the limestones of this system for those which lie adjacent. 



Owing to the remarkable position of the Taconic rocks, there is some danger of confounding 

 the limestone on the one hand with those of the Primary, and on the other with the Transition 

 rocks. Within comparatively a narrow belt there are four limestones, whose characters are 

 so nearly alike that they are often mistaken for each other, or not distinguished at all : 1st, in 

 the ascending order, is the true Primary limestone with graphite, lying closely along the border 

 of the Stockbridge limestone ; 2d, the Stockbridge, which being often sparry, and of a fine 

 texture, is mistaken for the true sparry limestone, or if coarse, for primary ; 3d, the latter 

 ranges along in pro.ximity to a limestone which replaces in part the grey sandstone of the 

 Champlain group. 



These four limestones being destitute of fossils, and not being very diverse in character, 

 but no more variable than is usual, are easily misunderstood, unless we first bear in mind their 

 real existence, and note carefully their position. The limestone of the upper part of the 

 Champlain gi-oup is often quite siliceous, somewhat sparry, but is never regularly or evenly 

 bedded ; and if the mass below is revealed, it will be found to be a reddish or grey sandstone. 

 The sparry limestone is quite even-bedded, of a grey color, very sparry, and is underlaid 

 by a fine argillaceous slate. The Stockbridge limestone is gi-anular, white or clouded, and 

 occasionally sparry, and either lies in the magnesian slate, or sometimes the granular quartz 

 appears on one side ; it is, however, always found in connection with marble, and I beheve 

 neither of the other limestones furnish this material. The Primary limestone is always unstra- 

 tified, and is in connection with hornblende, gneiss, granite, or some rock which is unques- 

 tionably primitive. Bearing in mind, therefore, the existence of these four limestones, the 

 order in which they lie with regard to each other, and the associated rocks, most of the diffi- 

 culty of distinguishing them will vanish. It is not to be understood that those limestones form 

 all of these continuous masses ; the oldest and the most recent are extremely irregular in their 

 appearance, while the remaining two will be found more constant than most rocks. 



Difficulties in distinguishing the slates of the Taconic system. — Analogous to the hmestones 

 spoken of above, are the slates of these rocks, and there are four liable to be mistaken for 

 each other: 1. The true talcose slate, associated with gneiss, hornblende, steatite or serpen- 

 tine. 2. The magnesian slates, also talcose, and not improperly considered as a talcose slate ; 

 its associations and connections are with granular stratified limestones and granular quartz ; 

 no hornblende, serpentine or steatite appears in connection ; a fact which has, however, been 

 before slated. 3. A fine aluminous slate, beneath the sparry limestone. This slate appears 

 in close proximity with the shales and slates of the Hudson river, making the fourth mass as 



