GEOLOGY OF MONA DNO CK MO UNTA IN I 3 



that these residuals are the result of two factors, erodibility and 

 location. In the case of Monadnock the second factor was 

 probably quite as important as the first. 



It must be noticed that this residuary peak does not stand 

 alone. The one farthest south in Massachusetts, and closely 

 related to this one, is Asnebumskit, in the town of Paxton, rising 

 about 400 feet above the peneplain or plateau of southern New 

 England. It is situated about a mile east of the divide between 

 the Connecticut and the Atlantic watersheds, and at the begin- 

 ning of that of the Blackstone. In preglacial times it was, very 

 likely, on the divide between the two main watersheds. This 

 monadnock is made up of a rusty, fribrolite schist,- not to be dis- 

 tinguished from that in hundreds of square miles of the surround- 

 ing plateau. Next to the north is Wachusett, with two minor 

 points associated with it, rising nearly 1,000" feet above the 

 plateau, and situated in the town of Princeton. This is on the 

 divide between the Ware and Nashua Rivers. It is composed of 

 granite and the same rusty, fibrolitic mica schist, the former 

 making up by far the larger part. There is nothing about these 

 rocks to indicate that they are any more resisting than are similar 

 granites and schists in the surrounding plateau. Watatic, situated 

 in the town of Ashburnham and rising about 700 feet above the 

 plateau, is another monadnock situated on this divide. With 

 the rocks of this mountain I am unacquainted. Then, crossing the 

 state line into New Hampshire, we find Monadnock also on the 

 same divide. There are more, though smaller, residuary peaks 

 east and west of this ; and to the north still others, even rivaling 

 Monadnock. This is just what might be expected, even in a 

 region made up of rocks of uniform resistance — incomplete pene- 

 planation up toward the sources of the main streams, while it is 

 almost complete farther to the south towards the mouths of these 

 streams. My conclusion from the study of the rocks is that 

 these monadnocks, situated along on the divide from central 

 Massachusetts into southern New Hampshire, owe their survival 

 to their position rather than to the rocks of which they are 

 composed; for in a region made up of rocks of uniform resistance 

 and subjected to peneplanation there would be some points up 



