NOMENCLATURE AND CONCLUSION. 57 



The whole series of beaches has been regarded as the work of one lake at 

 as many halts in the fall of its level. This is true in a wide sense, but there 

 were so many elements of change as the waters fell that it seems appro- 

 priate and necessary to consider the several stages as separate lakes and 

 £ive a special name to each. The waters changed their shape, size, and 

 level as they fell, and, what seems still more important, they changed the 

 place of their outlet several times. 



The need for the restricted use of the name lake Warren here proposed 

 is a natural result of the progress of discovery. With the finding of out- 

 lets and terminal moraines intimately related to the beaches, the moraines 

 marking the place of the ice-barrier that held the waters up, it becomes 

 a positive necessity to recognize the new facts, and this can be done best, 

 as it seems to the writer, by subdivision and restriction in nomenclature, 

 as is sometimes done in the biological sciences. The whole series of lakes 

 here described might be called the Warren lakes. This would be one 

 way of preserving Spencer's nomenclature; but, in the writer's opinion, 

 this use of the name would be unfortunate. A collective name ought 

 to have some geographic significance. The name Erie-Huron which is 

 used here serves this purpose admirably, and the name lake Warren may 

 then be applied in a more restricted way to that one of the several sepa- 

 rate lakes of the series which most closely corresponds to Spencer's 

 original idea. The Forest beach marks the widest extent of the Erie- 

 Huron glacial waters and was the last and most extensive lake of the 

 series. It seems more appropriate therefore to call this stage lake War- 

 ren than to apply this name to any of the higher, less extensive stages. 



Conclusion. 



The events of the glacial recession in the region of the thumb and the 

 Saginaw valley as revealed by the studies of the past season have been 

 presented above in the order of their occurrence so far as possible. It 

 seems hardly necessary, therefore, to restate them here. 



The larger part of the boundaries of the Erie-Huron glacial lakes had 

 been traced out by earlier observers before the observations here recorded 

 were made, but it happened that the thumb of Michigan, which was 

 critical ground for all the stages except the first or lake Maumee, remained 

 the last to be explored. If the relations of the moraines and beaches 

 and outlets are as given above, then outlets not certainly known before 

 have been found for three and possibly four of the stages, and these out- 

 lets are so related to the topography of the region and to the moraines 

 that in at least three cases there is no reasonable doubt as to the con- 

 temporary place of the ice-front. The continental ice-sheet was obvi- 



