SCIENTIFIC SURVEY. 275 



into siliceous slate. At Graves' Coffee House in the east part of 

 Holden, considerable mica is present in the quartz rock, with a 

 dip of 88° S. 60° E. Beyond this hotel the rock is very much 

 contorted and a local variation in the dip is 75° N. 00° W. But 

 the real north-westerly dip is apparent near A. B. Farrington's 

 house, two miles west. Here we have an argillo-micaoeous rock 

 dipping 50° N. 40° W., and a few miles further the ledges are en- 

 tirely quartz rock as far as the middle of Holden, dipping 65° N. 

 40° W. Cleavage planes are also present in great abundance, dip- 

 ping 80° S. E. We regard all the rocks mentioned thus far, away 

 from the granite, as essentially one formation of quartz rock, and 

 forming an anticlinal axis. The rock in the centre of the axis is 

 somewhat micaceous, and more nearly resembles the rocks west of 

 Holden village. If this is the true order of things, then we have 

 found a quartz rock underlying the great mass of schists between 

 Holden and Dover. Hence if future researches shall reveal occa- 

 sional bauds of quartz rock among these schists, especially if they 

 have an anticlinal form, we shall have a safe criterion to inform us 

 respecting the number of foldings in the whole area. Upon the 

 section / and / show the position of the two sides of the quartz 

 anticlinal, while the first g shows the more micaceous axis. We 

 do not suppose this axis can be of precisely the same age with 

 the micaceous rocks to the westward, because it underlies them in 

 association with quartz. 



We suspect that this quartz rock is the continuation of the 

 quartz rock of the Taconic series in Belfast, described in a previous 

 part of the report. That was associated with schists just like this, 

 and we find on a comparison of various disconnected observations 

 made between the two places, that a quartz rock, more jor less ob- 

 scure, can be traced with its associate schists all the way from 

 Belfast to Holden. This is a discovery of some importance, as will 

 be seen hereafter. 



Argillo-mica Schist. 



We next come to the largest and widest-spread of any formation 

 in the State, — to a rock that would receive different names from 

 different geologists. It would be called clay slate, talcose schist 

 or mica schist, according as the observer happened to inspect dif- 

 ferent portions of it. Last year we ranked it all as clay state, 

 epecifying many localities where talcose and micaceous varieties 



