EASTERN MASSACHUSETTS. 415 



the rock has assumed something of the appearance of gneiss, and would by 



some be chissed in that group of rocks The uniform dip away from the 



Quincy Hills, shown b}' all the stratified beds on their flanks, may be regarded 

 as sufficient proof that their elevation came after the deposition of these beds." 

 (Proc. Bost. Soc. Nat. Hist., 1869-71, XIIL, pp. 172-178.) 



While to one not acquainted with the geological structure of the re- 

 gion described, Professor Shaler's paper may appear conclusive ; the 

 facts, that the granite presents exactly the same intrusive relations to 

 the argillite that he says it should have if eruptive ; that he mistook for 

 sandstones and quartzites the Quincy granite itself; that the fossils in 

 the argillite show that its dip is diametrically the opposite of the one he 

 has assumed ; that his supposed ripple-mai'ks were the not uncommon 

 wavy fracture of granite ; and finally that his assumed stratification 

 planes are joint or structure planes, — leave his conclusions without any 

 foundation.* 



Professor Shaler points to the relations between the argillite and con- 

 glomerate as exposed while the excavations were being made for the 

 construction of the Chestnut Hill Reservoir. There he found that the 

 argillites lay beneath with conglomerate overlying, then more argillite 

 and above this the conglomerate, indicating it as probable that the argil- 

 lites and conglomerates in the vicinity of Boston form the same series of 

 beds, which he considered to belong to the primordial era. (I. c, p. 176.) 



In 1870, Dr. Hunt, on account of the finding of Eozoon Canadense in 

 limestones at Newbury (erroneously said to be in the adjoining town, 

 Newburyport) and Chelmsford, regarded the associated rocks as being of 

 Laurentian age, saying : — 



" These specimens from Chelmsford, it should be said, have been examined 

 and satisfactorily identified by Dr. Dawson. The argument from mineralogi- 

 cal and lithological resemblances in favor of the Laurentian age of tlie lime- 

 stone in question is therefore now supported by the undoubted presence in 

 them of Eozoon Canadense" 



The rocks about Newbury, which it will be recollected were united 

 by Prof. C. H. Hitchcock to the Cape Ann and Quincy hornblendic 



* In the preceding paper of Professor Shaler the misnomer of " Cambridge slates" 

 was applied to tlie argillites so well exposed in Soiuerville, and which properly should 

 have been called by tlie name of that city instead of Cambridge. The truth is, that 

 the locality from which they were named was erroneously supposed to be in Cam- 

 bridge, when in fact it is in Somerville. This locality was again erroneously said to 

 be in Cambridge in Professor Shaler's "Question Guide to the Environs of Boston," 

 1875, p. 20. No exposure of the argillite is known to exist in Cambridge, although 



