20-4: Proceedings Port. Soc. Nat. Hist. 



foregoing- surface deposits were laid down, there took place a 

 period of submergence when the whole coast stood at a much 

 lower elevation than at present. Shaler' gives three features 

 as criteria of submergence: fl) the remains of marine ani- 

 mals in stratified drift ; (2 ) the existence of stratified deposits 

 of sands and gravels where their formation could not be at- 

 tributed to fresh water lakes; and (3) a topography above 

 high tide level due to marine action. Evidence along these 

 lines is present in the Penobscot Bay region, but since Shaler 

 himself states that the second is the only really acceptable 

 evidence, that alone will be considered. On Isle au Haut 

 beach gravels occur up to a height of 225 feet,^ but above 250 

 feet no wave-washed stones have been found. This would in- 

 dicate that the land was submerged to a depth of between 240 

 and 250 feet. In addition the till on the faces and angles 

 of the hills and on the smaller islands has been extensively 

 denuded, a phenomenon which must be referred to marine 

 action. The above facts show that upon the withdrawal of 

 the ice from the immediate vicinity the sea must have stood 

 some 240 feet above its present level, and consequently much 

 of the present land area was under water and the rest ex- 

 tremely isolated. Although this condition existed to some 

 extent along the rest of the coast it must have been particu- 

 larly marked in the Penobscot Bay region, because of the 

 extreme irregularity of the shore line at this point. Both 

 the submergence and the isolation would lead to a limitation 

 of the flora which could reach these areas while on its north- 

 ward migration after the Glacial epoch. 



From its submerged condition the land has risen by a 



1. Recent Changes of Level on the Coast of Maine. Mem. Bost. 



Soc. Nat. Hist., Vol. II, Part III, No. Ill, 1874. 



2. See Stone, G. H., Mon. U. S. Geol. Surv., Vol. 34, 1889, p. 48. 



