Report of the State Geologist. 177 



there is a belt of silvery talcose slate, or magnesian slate, beyond 

 which the sparry limestone appears in a distinct range, which 

 may be located with some degree of precision, when it is stated 

 that the tunnel of the Great Western railroad passes through it, 

 which is not far from the line bounding ISTew York and Massachu- 

 setts. The members are regarded as the inferior rocks of the 

 Taconic system. Still west of them there is a wide belt of Taconic 

 slates, which contains many subordinate beds of limestone and 

 siliceous slate, and which frequently supports the outliers of the 

 lower members of the Xew York system. The Taconic system, as 

 a whole, may be regarded lithologically as an immense slate sys- 

 tem, with subordinate beds of sandstone and limestone, both of 

 which are more largely developed upon its eastern border adja- 

 cent to the Primary system." 



"The T^ew York system is colored like the former map, which 

 accompanies the volumes already distributed." 



N'otwithstanding the published discussions, controversial or 

 otherwise, regarding the Taconic system, which were carried on 

 during many years after this publication, no portion of the area 

 described in the map was ever carefully studied or mapped until 

 within recent years. Prof. Dana, Prof. Dwight, Mr. Ford and 

 Mr. Walcott have contributed to our accurate knowledge of this 

 region ; so that at the present time comparatively little remains 

 to be done to complete the work. 



During the later years also careful geological work has been 

 carried on in New Jersey and in Pennsylvania^, and the results 

 in the former are published in a carefully prepared geological 

 map, Avhile in the latter State the final map is in a forward state 

 towards publication. 



In the iinal discussions among the New York geologists pre- 

 paratory to the publication of the geological map and their final 

 reports, it was discovered that much remained to be done in 

 determining the relations between certain formations everywhere, 

 and more especially in the eastern part of the State. But as 

 only six months were allowed from the time of closing the field 

 work to the presentation of map and reports there was no time 

 or opportunity for review or revision. 



The proposition to recognize, upon the map, the Taconic system 

 proposed by Dr. Emmons, was rejected by Mr. Mather and 



