Shaler.] 174 ■ [December 3, 



dence of their sedimentary character. If these syenites were of igneous 

 origin, if they had been poured out before the deposition of the adja- 

 cent stratified beds, or thrust through them in a state of fusion, we 

 should expect to find the usual marks of such actions. In the first of 

 these cases the later sedimentary deposits would be found lying uncon- 

 formably upon the syenite without any indication of transition; in the 

 second we should expect to find a clear line of contact between the 

 syenite and the sedimentary rocks, such as is always to be found 

 where an intrusive mass of trappean matter cuts more ancient rocks. 

 What we do find is that the imperfect bedding of the deeper portions 

 of the syenite becomes more and more clearly defined as we pass 

 towards the exterior of the mass, and gradually passes into unques- 

 tionably sedimentary rock. Every stage of this transition is not 

 clearly seen, but enough is visible to satisfy any one that it really 

 exists. 



The first rocks, of quite unquestionable stratified origin, lie di- 

 rectly to the north of the Quincy syenite hiils, and consist of 

 clearly bedded sandstones, approaching quartzites in their character. 

 These rocks have an unknown thickness, probably amounting to 

 several hundred feet. Their general dip is northerly, with a varia- 

 ble angle of inclination which may be roughly averaged at twenty de- 

 grees. Above them the section is hidden for a distance which would 

 give space for about three hundred feet of beds. Running the same 

 north course across the break, we come upon the lowest of the Brain- 

 tree series. This part of our section has a total thickness of about 

 two hundred feet; its dip corresponds with the general inclination ob- 

 servable in the supposed stratification of the syenite, as well as that 

 of the quartzites immediately above it. The whole of this Braintree 

 series is fossiliferous, although it is only in about one hundred feet of 

 the upper part that well preserved specimens of the characteristic 

 fossils are found. It is composed of beds which were evidently at 

 the time of their formation very uniform mud of a sea floor tolerably 

 remote from land; and although much changed by metamorphic action, 

 it is easily perceived that the whole set of beds contains no trace of 

 shore deposits. Immediately beyond the exposure of the Braintree 

 beds at Hay ward's Landing, a dislocation has brought the thin 

 bedded quartzites again to the surface. The alteration in these is so 

 great that the rock has assumed something of the appearance of gneiss, 

 and would by some be classed in that group of rocks. 



If there be no undiscovered faults in the section from the Quincy 



