370 GEOLOGY OF THE NARRAGANSETT BASIN. 



lying sandstone indicates also a southward pitch, and a westward dip on 

 the western side of Beacon Hill. In a field west of Miantonomy Hill, near 

 the railroad, coarse conglomerate dips 45° E., suggesting a synclinal 

 structure between the conglomerate exposed in the field and that on the 

 hill. This interpretation would demand an anticlinal structure west of the 

 first-named exposure, a synclinal structure coming in again at Coddington 

 Point and Coasters Harbor Island, where coarse conglomerate again 

 appears, that of Coasters Harbor Island bearing the closest resemblance to 

 that on Miantonomy Hill. 



This interpretation of the geological structure is again very free, and 

 is based upon two assumptions: That the conglomerate exposures on 

 Miantonomy Hill and those at Coasters Harbor Island, lithologically alike, 

 are also stratigraphically identical, and that the field exposures of con- 

 glomerate which dip eastward possibly belong to the same horizon. 



Possibility of two horizons of conglomerate at Miantonomy Hill. Wily, llOWeVei', should 



there not be two horizons of conglomerate, the exposures west of Mianto- 

 nomy Hill underlying the coarse conglomerate forming the summit of that 

 hill? The occurrence of coarse conglomerate low down in the Aquidneck 

 series — in fact, according to our interpretation, at its base, in the western 

 part of Bristol Neck — shows the possibility of coarse conglomerate lower 

 than that which forms the summit of the rock of Carboniferous age in the 

 Narragansett Basin. Possibly this exposure west of the hill is such a lower 

 horizou, although not near the base of the shale series. 



On the western side of the stream entering Eastons Pond from the 

 north, in the fields north of the first east-west road, is a conglomerate 

 exposure apparently dipping very low to the westward, so that the dip 

 would evidently carry also this conglomerate beneath the conglomerate 

 forming the summit of Miantonomy Hill. The exposure of conglomerate 

 north of Eastons Pond might therefore correspond to the section west of 

 Miantonomy Hill, the two forming a lower horizon of conglomerate, while 

 the Miantonomy Hill exposure formed the upper horizon. To which of 

 these two horizons would the Coasters Harbor Island conglomerate 

 belong! The writer interprets it as corresponding to the Purgatory 

 conglomerate. Its resemblance to the conglomerate near the summit of 

 Miantonomy Hill is so great as to be considered conclusive of identity, 

 notwithstanding the fact that conglomerates corresponding to these expo- 



