THE LYMAN SCHISTS OF NEW HAMPSHIRE 379 



2. Locally it contains angular blocks and sometimes isolated 

 pebbles. 



3. It grades into the fine variety of Lyman conglomerate schist. 



4. It has obscure bedding (layers differing in texture) in some 

 places. 



5. There are all gradations in size between its largest and small- 

 est particles. 



6. There is a relatively small proportion of small grains as 

 compared with the porphyry schist. 



This Parker Hill white schist certainly was never a normal 

 clastic in the ordinary sense of the term. It might be called an 

 arkose schist on account of its having abundant clastic feldspar. 

 However, its more or less intimate association with effusive rocks, 

 the presence in it of the constitutents of the porphyry schists, both 

 as small particles (quartz and albite grains, etc.) and as larger 

 fragments (some whitish like the Lyman schists and some dark 

 like the Parker Hill dark schist), and the observed gradations 

 between it and the fine Lyman conglomerate schist which is com- 

 posed chiefly of sheared pebbles of felsitic nature — these facts 

 induce me to classify the rock as a metamorphosed tuff. 



Conglomerate schist of the Young's Pond locality. — There is no 

 doubt that this "schoolhouse conglomerate" looks very much like 

 a glacial deposit, as stated by Hitchcock 1 and recently by Sayles; 

 but if the accepted criteria for till ever did exist here, they have 

 been entirely destroyed by metamorphism. For this reason it is 

 futile to look for signs of glacial abrasion on an underlying rock 

 pavement. The weakness of the evidence for glacial origin was 

 fully appreciated by Mr. Sayles, and I may add. that evidence 

 against such glacial origin is almost, if not quite, as inconclusive. 

 However, one should bear in mind that great variation in size of 

 constituent fragments and absence of bedding are characters shared 

 by talus, landslide debris, pyroclastic materials, and not infre- 

 quently even by river-laid alluvial cone deposits. Is it not more 

 probable that the "schoolhouse conglomerate," being closely asso- 

 ciated with an effusive rock (quartz-plagioclase porphyry schist), 



1 C. H. Hitchcock, "New Studies in the Ammonoosuc District of New Hampshire," 

 Bull. Geol. Soc. Am., XV (1904), 472, and Geology of New Hampshire (1877), II, 302. 



