Hill: Penobscot Plants. 205 



series of uplifts, some longer than others, to its present ele- 

 vation — a movement which may still be in progress. The 

 present period of relative quiescence, however, seems to have 

 been much longer than any of the preceding halts in the 

 process, and there is considerable speculation as to whether 

 the coast line may not be stationary at the present time or 

 even slowly sinking again. Owing to the rocky nature of the 

 shores evidence on this point is extremely slight, and the 

 little that does exist is so controlled by local conditions as 

 to be worthless in a consideration of the general problem. 

 Indeed, conditions in one locality point toward the subsidence 

 theory, while in others exactly the opposite is the case. 



The post-glacial history of the region is as yet very brief. 

 Only a few deposits are present, chiefly beach sands and 

 gravels, swamp muck and peat. As the ocean is constantly 

 eroding the l)ed-rock and the till and clay, parts of this 

 weathered material are deposited at low elevations in 

 shallow indentations as sand or gravel beaches or as mud 

 flats. On the outer islands where the shores are rocky the 

 beaches are formed, and inland, where the surficial deposits 

 are within reach of the waves, mud flats are the rule. Sandy 

 beaches are rare enough to be curiosities, occurring only along 

 the shores of a very shallow bay on the southern side of 

 Swans Island. 



As has been stated previously, the swamp muck and peat 

 have developed in the poorly drained depressions on level sur- 

 faces. Here their work of converting the ponds and swamps 

 into dry land is constantly going on. 



Climate 



It is not to be expected that climatic factors, which are 

 operative only in broad areas, could render conditions in the 



