284 GLACIAL GEAVELS OF MAINE. 



BOWLDER FIELDS AND TRAINS. 



Many details as to the till are here omitted, as not bearing on the sub- 

 ject of the glacial gravels. One phenomenon must, however, be noted — 

 the bowlder fields. In a certain sense the whole of the granitic regions 

 might be considered as bowlder fields. But the fields referred to are dif- 

 ferent. They lie in regions of coarse slates. The whole surface is so cov- 

 ered by slabs, up to 6 or 8 feet long, that one can travel a half mile by 

 stepping from bowlder to bowlder. The only soil is found 2 to 5 feet below 

 the surface. The babbling of invisible streams is heard as they make their 

 way among the bowlders. Raspberry bushes peer up through the rifts 

 between them. One of these bowlder fields is found about a mile south of 

 Tomah station of the Maine Central Railroad. This is situated near the 

 junction of two large glacial rivers, and the finer parts of the till may have 

 been washed away by the waters. I observed a still larger bowlder field 

 in T. 7, R. 4, Aroostook County. It is situated 2 miles from any known 

 osar, and its cause is obscure. 



In the wilderness between Aurora and Deblois a train of huge g-ranite 

 bowlders, which is parallel with the g'lacial scratches of the region, is inter- 

 sected obliquely b}'' the Katahdin osar. The bowlders are piled one above 

 another so as to form a ridg'e, and some of them overlie the gravel. The 

 bowlder trains bear a relation to outcrops of granite rocks, but are not lateral 

 to valleys. The appearances indicate that they were not medial or lateral 

 surface moraines, but either distinctly subglacial or stranded basal matter, 

 so that in their ridge-like development they are drumlins of coarser material 

 than the ordinary. 



WAS THERE MORE THAN ONE GLACIATION OF MAINE ? 



The observations of "White, Winchell, Upham, Chamberlin, Salisbury, 

 McGee, and others in the Upper Mississippi Valley prove that there were at 

 least two principal advances of the ice, separated by a rather long interval. 

 It has since been a special object of search to Eastern geologists to find 

 similar advances in the Northeast. At one time it appeared probable that 

 I had found traces of two tills that might belong to diiferent periods. The 

 dam of the Penobscot River where it flows out of kSouth Twin Lake had 

 broken a short time before my visit to the place. The water had escaped 



