EASTERN MASSACHUSETTS. 411 



magnesian serpentine, or verd antique marble. The syenite was said 

 to pass into greenstone often by insensible shades. This paper locally is 

 of considerable value. The red felsite of Saugus was described as jasper. 

 In 1854 the limestones of Eastern Massachusetts were refeiTed to the 

 Devonian by Dr. Hunt, who remarks as follows : — 



" In the fourth class we include the crystalline limestone of eastern Massa- 

 chusetts, which occurs in a great number of places in the towns of Bolton, 

 Boxborough, Chelmsford, Carlisle, Littleton, Acton, Natick and Sherburne. 

 It appears according to Hitchcock, in interrupted lenticular masses, lying in 

 the gneissoid formation, or in the hornblendic slates, and occasionally present- 

 ing distinct marks of stratification. Stdl farther east at Stoneham and New- 

 bury, we find crystalline limestone, sometimes magnesian, in irregidar masses, 

 lying in a rock intermediate between syenite and hornblende slate. Serpen- 

 tine is found vnih that of Newbury ; and at Lynnfield, a band of serpentine 



has been traced two or three miles N. E. and S. W We have now to 



inquire as to the geological age of this great mass of crystalline rocks which is 

 so conspicuous in Eastern New England "When we consider the geo- 

 graphical position of the Upper Silurian rocks in the Connecticut valley on the 

 one hand, and the coal fields of southeastern Massachusetts on the other, we 

 can scarcely doubt that the intermediate gneissoid, and hornblendic rocks, with 

 their accompanying limestones, are the Devonian strata in an altered condi- 

 tion." (Am. Jour. Sci., 1854, (2) XYIII., pp. 198, 199.) 



As late as 1863 the same view of the age of these limestones was 

 held; while in 1861 Dr. Hunt especially stated, that we recognize 

 nothing in New England or southeastern Canada lower than the Sihc- 

 rian system." (Am. Jour. Sci., 1861, (2) XXXI., p. 403 ; 1863, XXXVI., 

 p. 225 ; Geology of Canada, '^63, p. 592.) 



lu 1856 the first definite knowledge of the actual geological position 

 of any of the rocks in the vicinity of Boston was obtained. Specimens 

 of a trilobite, belonging to the genus Paradoxides, and a characteristic 

 fossil of the Primordiid, or Potsdam group of the Lower Silurian, had 

 for many years been in the hands of scientific men in Boston ; but the 

 locality from which they had been obtained was not known. Finally, in 

 1856, the attention of geologists was called to these trilobites by the 

 proprietors of a quarry in the argillite at Braintree, and the first notice 

 of the occurrence of these fossils, and of their true locality, was given to 

 the public by Prof. W. B. Rogers. (Proc. Bost. Soc. Nat. Hist., 1856, 

 VL, pp. 27-30, 40, 41, 217; Am. Jour. Sci., 1856, (2) XXII., pp. 296- 

 298; Proc. Am. Acad., TIL, pp. 315-319.) 



Professor Rogers describes the argillite as being included between 

 large masses of igneous rock, or syenite, and a dipping N. 20° "W., at an 



