EASTERN MASSACHUSETTS. 



411 



magucslan serpcntliiOj or vcrd antique marblo. TIic syenite was said 

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

 of considerable value. The rod folsite of Saugus was described as jasper. 

 In 1854 the limestones of Eastern Massachusetts were referred to the 

 Devonian by Dr. ITunt, who remarks as follows : 



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

 chueetts, which occurs in a great number of places in the towns ^of Bulton, 

 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. Still farther east at Stoneham and New- 

 bury, we hud crystalline limestone, sometimes magnesian, in irregular masses, 

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

 tine is found with that of Newbury ; and at Lynn field, a band of serpentine 



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



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

 so conspicuous in Eastern New England When wc consider the geo- 

 graphical position of the U}»per Silurian rocks in tlie Connecticut valley on the 

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

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

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



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



As late as 18G3 the same view of the age of these limestones was 

 held; while in 18G1 Dr. Hunt especially stated, that we recognize 

 nothing in New England or southeastern Canada lower than the Siht' 

 rian system.:' (Am. Jour. Sci., ISOl, (2) XXXL, p. 403 ; 18G3, XXXVL, 

 p. 225 ; Geology of Canada, 18G3, p. 592.) 



In 185G the first dcfuiite 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 characteristio 

 fossil of the Primordial, 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 

 185G, the attention of geologists was called to these trilobitcs by the 

 proprietors of a ipiarry in the argillite at Braintreo, and the first notice 

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

 tlie public by Prof. W. B. llogers. (Proe. Post. Soc. Nat. Hist., 1856, 

 VL, pp. 27-30, 40, 41, 217; Am. Jour. Sci., 185G, (2) XXIL, pp. 29G- 

 298; Proc. Am. Acad., IIP. 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 



