1884.] 3b [Bouv^. 



above it in our day, or even that upon the broken upturned 

 strata of the slate, conglomerate should be found resting in un- 

 conformable position notwithstanding the general condition is 

 that of the latter overlying conformably the former. Moreover, 

 it is altogether likely that whilst the slate was in process of for- 

 mation the boulders and pebbles of the elevated lands surround- 

 ing the basin area may have been carried into it by the wash of 

 the waves at their base, by descent of waters from the adjacent 

 hills or by igneous disturbances leading to the local production of 

 more or less conglomerate upon the slate near the borders of the 

 basin. 



As suggested in the beginning of this essay, it was to aid in the 

 solution of the question as to the relative age and position of the 

 rocks of the Boston basin that led my mind to dwell at all upon 

 its probable origin and history. The view I have presented 

 seems to me a reasonable one. If admitted in the main to be 

 correct it must set at rest all question as to which is, as a general 

 fact, the underlying rock, and it likewise determines the deposits 

 of both the conglomerate and slate to have been contemporan- 

 eous. 



I have no desire to keep from mind the objections that may be 

 brought to such a view. Ons may be that the quartzites of the 

 ancient formations, pebbles of which are common in the conglom- 

 erate, would not have been readily acted upon by the dis- 

 integrating action that affected other rocks. This cannot be 

 considered as certain until more is absolutely known than now, 

 not only of the actual character of the atmosphere but of the 

 menstruum that permeated the rocks during the period of the 

 great disintegration. That this menstruum may have been 

 strongly alkaline is not unlikely in view of the extensive decom- 

 position of feldspathic formations, and if so the quartzose strata 

 would suffer decay with the others. The so-called quartzite was 

 then without doubt simply a friable sandstone and possibly con- 

 tained a considerable admixture of other grains than those of 

 pure quartz, which would help to facilitate its destruction. 



That the tendency of a rock of this character to form concre 

 tions upon exposure to the elements and other agencies and thus 

 yield spheroidal forms is, I think, demonstrated by observations 

 of Dr. Wadsworth upon the St. Peters and Potsdam sandstones, 



