TABLE OF CONTENTS. Vll 



C. H. Hitchcock demonstrates the iniportiince of mineral characters in the 

 classilication and identification of rocks, 393 ; tlie rocks of Ni,-\v liuinpsliiro 

 classified on that basis, 393 ; Hunt called on by C. H. Hitchcock to decide 

 which way the porithyritic gneisses dip, 394 ; Huntingtox points out facts 

 indicating that the Concord granite is intrusive, 394 ; C. H. Hitchcock states 

 his views in Final Report, Vol. II., in regard to the impoitiiuce of not "obscur- 

 ing observations" by "individual speculations," 394, 395; some results of 

 investigations made to ascertain how far C. H. Hitchcock was able to distin- 

 guish and properly name rocks, 395-397 ; authenticity of specimens examined 

 by us, 397 ; notice of our tabular view of the classifications presented at various 

 times by the New Hampshire Survej-, under C. H. Hitchcock, 397, 398. 



EASTERN MASSACHUSETTS. 



S. GoDOx's observations in 1807-8, 398 ; his division of the formations in the 

 vicinity of Boston, 398-400 ; Maclure's geological map, 400 ; error of HcxT 

 in describing Maclure's work, 400 ; J. F. and S. L, Daxa's contribution to the 

 geology and mineralogy of the region near Boston (1818), 401, 402 ; Eatox'.s 

 Index to the Geology of the Northern States, 402 ; Thomas Coopeii, 1822, 

 recognizes the volcanic character of some of the rocks near Boston, 403 ; Hitch- 

 cock'.s first publication (1824) in regard to geology of Eastern Massachusetts, 

 403 ; Hitchcock contributes to the geology of the same region in Eaton's Survey 

 of the Erie Canal, 403, 404. J. W. Webster, 1824-25, publishes Remarks on 

 the Geology of Boston and its Vicinity, 404. Hitchcock's Report, 1833, and 

 his theoretical views as set forth in that volume, 405-409 ; his final report, 

 1841, 409, 410 ; his theories set forth and commented on, 410. Puescott's 

 geological investigations in Essex County 839), 410. 



Hunt, in 1854, refers the limestones of Eastern Massachusetts to the Devonian, 411 ; 

 he states, in 1861, that he recognizes in New England or Southeastern Canada 

 "nothing lower than the Silurian," 411. Discovery of fossils near Boston, and 

 recognition of the locality from which they came, 411 ; various statements as to 

 the dip of the rocks from wlucli these fossils came, 411, 412 ; HuxT, in 1866, 

 on the limestones of Eastern ilassachusetts, considering it doubtful whether 

 they may not be Laurentian, 412 ; C. H. Hitchcock, 1867, considers the gneiss 

 and hornblende schist of Andover to "belong to the Eozoic ages," 412; his 

 reported facts doubted, 412. Huxt, in 1869, describes the granite of New Eng- 

 land as being a sedimentary rock, and containing traces of fossils ; in 1870 he 

 says that the granites of Cape Ann and Quincy are "probably intrusive" ; in 

 1873, that the granites of Rockport are '* distinctly eruptive," 413; necessary 

 physical conditions resulting from Hunt's theories, 413 ; Bickxell finds 

 Eozoon in limestone at Newbury, 413, 414 ; Hunt considers this proof of the 

 Laurentian age of these rocks, 414. 



Siialeu, in 1869, considers the stratified origin of the syenites of Eastern ^lassachu- 

 setts clearly proved, — the syenite being seen to pass into " unquestionably 

 sedimentary rock," 414 ; his geological observations shown to be incorrect, 414. 

 Hunt, in 1870, considers the finding of the Eozoon at Chelmsford, and its 

 identification by Dawson, as proof of the Laurentian age of the limestones of that 

 region, 415 ; Hunt, in 1870, refers the gneiss of Eastern Massachusetts to tlio 



