FOKMATlOiSr OF AKKOSES. 51 



materials derived from crystalline rocks wliicb have been subjected to imich 

 decay in place, so that tliey lost their original cohesion before they were 

 subjected to trausj)ortation and were accunuilated in their present situations. 

 The essential characteristic of such deposits is that they contain considerable 

 quantities of crystalline materials in which the fragments have not been 

 reduced to sandy but retain, in good })Hrt at least, their original form. In 

 other words, the presence of arkose beds means an antecedent decay in 

 crystalline rocks, a decay taking place in such a manner as to loosen the 

 crystals from their attachments without going far enough to disintegrate 

 the bits. This action has been followed by the wearing away of the 

 softened mass and the more or less complete rearrangement of the 

 materials. 



In the present state of the study of arkose beds, pains has not been 

 taken to discriminate the materials into the two groups into which they may 

 naturally be divided. In certain cases, after the process of decay has 

 broken up the texture of the crystalline rock, and perhaps removed much 

 of its materials in the state of solution, the deposit remains essentially in 

 its original place, where it may be covered by subsequently accumulated 

 deposits. Even though recementation of the crystals takes place, the 

 accumulation will have more or less of the character to whicli we gave the 

 name of arkose. For convenience, we may class this group as unremoved 

 arkose. 



Although the (conditions which favor the formaticm of unremoved 

 arkoses must be of infrequent occurrence, instances of the kind are to be 

 observed in certain parts of New England, where the preglacial decay 

 reduced considerable quantities of the cr3^stalline rocks to a disintegrated 

 state, and where the beds thus softened were not removed by the glacial 

 wearing, but remain to the present day covered by sheets of stratified or 

 unstratified drift. The normal or transported arkoses can, in all cases, be 

 discriminated from those which liave remained in place, by' the evidences of 

 w^ater action afforded by more or less obvious stratification. 



The niost characteristic and readily interpretable deposits of arkose 

 exhibited witlnn the limits of the Xarragansett Basin, indeed one of the 

 most important accumulations of this nature ever described, occurs at Steep 

 Brook, the station just north of Fall River, Massachusetts. At this point, 

 Ivino^ a"*ainst the OTanitic rocks which form the western margin of the basin, 



