148 



ceous be'ds with the argillite of the Nashua Valley. If this is 

 done, then it is clear that the conglomerate portion of the Bel- 

 lingham series is the stratigraphic equivalent of the Harvard 

 conglomerate ; the conglomerate in both cases coming between 

 the mica slate below and the argillite above, and not being well 

 marked off from either. As in Harvard, so in Bellingham, 

 the most of the conglomerate has suffered more or less exten- 

 sive alteration ; and this brings us back to the main point, viz., 

 to the bearing of these altered rocks, in the last-named town 

 especially, on the origin of the underlying schists and gneiss. 

 In this connection, the interest attaches chiefly, though not 

 entirely, to the conglomerate. 



The metamorphic process here is substantially the same as 

 that which has been so fully described and illustrated by Prof. 

 Edward Hitchcock, 1 in connection with the conglomerates of 

 Plymouth and Wallingford, Vermont, and Newport, R.I. ; 

 also by Mr. George L. Vose, 2 as characterizing the conglom- 

 erate in the vicinity of Rangely Lake, in Maine ; and, later, 

 by Mr. L. S. Burbank, 3 in his researches on the Harvard con- 

 glomerate. It consists essentially, in every case, in the flat- 

 tening or drawing out of the pebbles into thin, lenticular layers, 

 which interlace and give rise to a distinctly schistose structure. 

 The deformation of the pebbles, in Bellingham at least, is an 

 undeniable fact ; and no one who has seen the rock will hesi- 

 tate to admit it. In this locality, however, it is quite evident 

 that the metamorphism has been mainly a drawing-out or 

 stretching, rather than a flattening process ; it is as if the peb- 

 bles had experienced an endwise pull, instead of compression 

 by a force exerted in one direction only. The typical form of the 

 distorted pebble is not a lenticular layer, but a spindle-shaped 

 rod, which is sometimes nearly cylindrical or prismatic, and 

 usually presents transverse sections of similar shape in all 

 parts of its length. The pebbles are all elongated in the same 



i Am. Jour. Sci. (2), xxxi., 372. 

 'Memoirs Bost. Soc. Nat. Hist., I., 482. 

 «Proc. Bost. Soc. Nat. Hist., xvm., 224. 



