80 GEOLOGY OF THE ^"AERAGANSETT BASIJST. 



section in which they lie incHnes the observer to the opinion that they are 

 the equivalents of the uppermost at the mines on Aquidneck Island; but 

 this opinion has little evidence to support it. 



Many other deposits of coal have been occasionally exposed in various 

 parts of the field in which the carbonaceous strata occur. Some of these, 

 as, for instance, the beds at Bristol, have been made the objects of experi- 

 mental mining. The last-named deposit is, from its position, to be reckoned 

 in the group occurring in the northern part of Aquidneck, but the greater 

 part of these little-known occurrences can only be placed as below the 

 upper conglomerate. 



CONDITION OF BEDS. 



As none of the coal beds of this district have been worked for many 

 years, the accounts of the deposits can not be made anew. The writer has 

 seen the bed which was last worked at the Aquidneck mines, and also that 

 at Valley Falls, which to within a few years ago was mined for ^^ foundry 

 facings," and also that which was in a small way exploited at Cranston in 

 an unavailing effort to market it as fuel. From these observations and 

 the imperfect records which exist of the facts concerning the other deposits, 

 the following statements may be made as to the physical conditions of the 

 deposits. 



The coal beds of this area probably number a half dozen or more, of 

 which only those of the Aquidneck group have been proved to have much 

 continuity. Owing to a feature which, so far as observed, they all present, 

 the thickness of none of these beds can be accurately determined. This 

 feature is the pecuHar ^'rolling" to which the carbonaceous material has 

 been subjected in the dislocation of the beds of which it forms a part. In 

 practically all cases the beds above the coal have been by the process of 

 metamorphism brought into a very compact and rigid state. This change 

 appears to have taken place before or during the development of the folds 

 into which they have been cast. As the process of dislocation went on, the 

 irregular strains acting on the relatively Httle resisting coal caused it to 

 creep toward the points of least pressure. The result was that wherever 

 the bed has been followed in the direction of the dip for a considerable 

 distance the layer is found to widen and contract, so that in a variable length 



