388 



THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



favorable localities, as well as that furnished by allied rocks in other lands 

 where they have been more thoroughly investigated, must at present be deci- 

 ■ (Geol. of New Hampshire, III, Part IV. p. 1 05.) 



sive. 



This rock was accepted by Dr. T. Stcrry Hurit as Norian in 1873 

 (Proc. Bust. Soc. Nat. Plist, 1873, XV. p. 310), but in 1878 he re- 

 mai'kcd : 



" The labradoritic rocks in the White Mountains, which had by Hitchcock 

 been referred to norite, are now found by him to be eruptive masses." (Azoic 

 llocks, p. 101.) 



In a paper by Prof. Hitchcock (Am. Jour. Sci., 1872, (3) III. pp. 43- 

 47), on the '^Norian Kocks in New HanipHhirc/' the following is ad- 

 vanced to show their sedimentary origin : 



" The first rock Rcen is a gneiss with nodular orthoclase, dipping by compass 

 about 80°, S. 70° W. The strata are indicated by folia of a dark hyperstlienic 

 mineral, often forming bunches or nodules. Jointed planes di[)ping about 25° 

 westerly might be mistaken for strata.* One might be so easily deceived, that 

 it seems as if thev must be the Tilanes described at the Cascades and on Mount 



Osceola by J. P. Lesley A few rods higher up the stream -, . . • the 



first ledge of the lal^radorite rock appears It is a perplexhig matter to 



determine the lines of stratidcation, as the outcrops are divided by two promi- 

 nent sets of jointed planes, either of which miglit be called layers of deposition, 

 the rock being essentially homogeneous. One set dip about 20° northeidy and 

 are the most numerous. The other di}) about 75°, W. 10° S. The latter cor- 

 respond better in position to the gneissic strata first seen than the ibrnier." 



In the Report for 1871, published in the summer of 1872, we have 

 the following statements regarding the same rocks : — 



"The first rock seen was called gneiss with nodular orthoclase, with its sup- 

 posed strata dipping by compass 80° S. 70° W the presumption arises 



that these so-called strata may be bands of mica whose planes do not corre- 

 spond with those of accumulation, but have been superinduced during the meta- 

 morphism of the rock. The jointed planes dipphig about 25° westerly would 

 be those of stratification, if the rock is stratified. These were pointed out by 

 J. P. Lesley. A few rods up Norway Brook appears the first ledge of the Ossi- 



pyte [the labradoriteor Norianrock] Considered as an isolated case it 



is difficult to determine the planes of stratification since two prominent sets of 

 jointed planes exist, either of which might be taken for strata. Oiu; set dip 

 about 20° northerly, and are the most numerous. The other dip about 75 

 W. 10° S. As the latter correspond better in position with the supposed 

 strata of nodular gneiss, it was thought they indicated the proper lines of 



* Same statement in Atlas of Now Ihunpshirc, 1877, p. 11. 



^-^,0 



