254 THE JOURNAL OF GEOLOGY. 



extreme case about twenty miles. The ice would be so long 

 passing over such distances that we could expect that the basal 

 water would restrict the enlargement of the tunnels sufficiently to 

 show a characteristic development of the gravels, such as narrow- 

 ness of the osars or gaps without gravels. While in such situa- 

 tions I nowhere find so extreme a development as in the coastal 

 region, yet there are numerous facts that are best interpreted by 

 the hypothesis that the basal waters of the slack water dams in 

 the subglacial tunnels did somewhat obstruct the enlargement 

 of the tunnels ; and thus far I have found none inconsistent with 

 that hypothesis. 



The critical reader will have noted that the belt of transition 

 of the coastal gravels of Maine is approximately parallel to the 

 ice front at one stage of the retreat of the ice. It is also some- 

 what parallel to the southern margin of the n^vL It has been 

 necessary to consider whether the coastal gravels were retreatal 

 phenomena, connected with some late stage of the ice sheet's 

 history, also what effect would be produced by the retreat north- 

 ward of the 7iJvi line, whether the discontinuous gravels were due 

 to the gradual rise of the sea, etc. The result has been to rele- 

 gate all the suggested agencies to a subordinate position with 

 respect to the two causes above named — a probable small 

 acceleration of ice flow near the coast and the limited enlarge- 

 ment of the subglacial tunnels over the area whose basal ice 



was submerged in the sea. 



George H. Stone. 



