120 
CONTRIBUTIONS TO THE GEOLOGY OF MAINE. 
[bull. 165. 
CASTLE HILL TUFFS. 
The most favorable place for the study of these rocks is in the open 
fields and along the roadside about one mile west of Castle Hill Hotel, 
where they are found well exposed, in close connection with the andes- 
ites, on lots 31 and 32 (see map, fig. 6). 
Normal type. — While the southern Castle Hill tuffs differ consider- 
ably from one another in external and microscopic appearance, they 
are essentially alike and will be roughly classed together as the normal 
type. 
The outcrops of this type occur as low knobs or swells of land, always 
quite limited in extent and never forming marked topographic features. 
ET\^T3 
Fig. 6, 
Normal tuff. 
-Map of Castle Hill area. 
Siiicified tuff. 
As might be expected in rocks of this class, the exposed surfaces show 
much alteration to a loose, porous rock, easily crumbled between the 
fingers and having the appearance of partly consolidated sand. 
Embedded in the tuff are many fragments of igneous rock, consisting 
mainly of rhyolite, vesicular andesite, and ashy or pumiceous frag- 
ments averaging about a quarter of an inch in longest diameter, but 
pieces are found as large as 6 by 10 inches. Corals and brachiopods are 
also found sparingly distributed in the coarser tuffs. On that part of 
the ridge known as Richardson Hill a conglomeratic facies is found in 
addition to the normal type. 
