52 GEOLOGY OP THE NARRAGANSETT BASIN. 



is a section of what at first sight appears to be a mass of granite which has 

 decayed in place. This seemed to be the view which was enforced by the 

 observed facts when these beds were first seen by me, about twenty-five 

 years ago, and they had just been opened by prospectors who were led by 

 a small outcrop on the brook to seek for fire clays. Further exploration, 

 however, soon disclosed the fact that the mass exhibited traces of stratifica- 

 tion such as were not to be found in the neighboring unchanged granite. A 

 close study of the obscure divisional plane brought to light the existence 

 in them of many well-preserved specimens of plants which belong to the 

 Carboniferous time. This evidence indicates that the deposit was formed 

 during the period of the Coal Measures. The considerable thickness of this 

 section makes it clear that the conditions which led to its formation continued 

 for a long time. These conditions were substantially as follows: There was a 

 rapid importation of semidecayed granitic rock, such as would be afforded by 

 the decomposition of the crystalline materials which are to be found immedi- 

 ately to the east of the locality. The rateof this accumulation appears to have 

 been so speedy that there was no chance for a true soil layer to be formed 

 on the growing beds. The plant remains which occur were evidently not 

 grown on the sites they now occupy, but were fragments swept into their 

 positions from a distance. It appears likely that they had been to a greater 

 or less degree inclosed in ordinary ferruginous concretions before this 

 transportation. 



The interpretation of the conditions at Steep Brook during the time 

 when the forces which led to the deposition of the arkose were in action 

 seems, in a general way at least, to be not at all difficult. It is evident 

 that in the time preceding the deposition of the portion of the Carboniferous 

 strata on which the arkoses lie, the portion of the continent about the Narra- 

 gansett Basin had been long exposed to atmospheric decay without having 

 been subjected to the conditions which would remove the decomposed 

 material as rapidly as it was brought into the disintegrated form. Judging 

 by the conditions which have affected the fields that now afford or that 

 might produce the arkose deposits, we may assume that these levels of the 

 Coal Measures time had long been the seat of a considerable rainfall and 

 had maintained a coating of vegetation, such being the antecedent condi- 

 tions of any decomposition which would prepare the way for arkoses. 

 After the development of a sufficient depth of this rock decay, we have to 



