176 BULLETIN OF THE 



sedimentary origin will be noticed ; although they are quite numerous, 

 they are comparatively small. Mr. Crosby was the first to notice the 

 stratification of these rocks, and pointed out the locality at Dungeon 

 Rock, Lynn, where the material is fine, and apparently all derived from 

 the felsites. Another similar locality in which the stratification is well 

 marked occurs along the water-pipe between the reservoir and the water- 

 works, Lynn. In these areas it is almost impossible to tell, upon a 

 weathered surface, that the rock is fragmental. These exposures were 

 accidentally brought to light by quite extensive excavations, and it is 

 possible that some of what is now regarded as felsite may be a recom- 

 posed rock, so like felsite (from which it was made) in its external 

 appearance as not to be distinguished from it by the unaided eye. The 

 area of porodites and conglomerates of Vinegar Hill and Pirates' Glen 

 is probably the largest area of these rocks in this region. In the same 

 locality there are several small patches of granite mixed with the frag- 

 mental rocks which are in places distinctly stratified. 



One of the most interesting exposures of the stratified porodites is 

 upon a high hill, a short distance south from Saugus, and near the east 

 side of the road leading to Sweetser's Corner. The greater portion of 

 the hill is felsite, but upon its northern slope occurs the most beautiful 

 coarse tufix of this region. It is tilted so as to be standing nearly or 

 quite vertical, with a strike N. 70° E. At this place the thickness, 

 measured directly across the strike, is about 150 feet, and may be greater, 

 but for want of exposures the excess beyond 150 feet cannot be deter- 

 mined. This is the only locality we have found to furnish an opportu- 

 nity to determine the thickness of the fragmental rocks. 



An exceptional conglomerate occurs a short distance west of the 

 Saugus station, near the railroad. Its peculiarity consists in its associa- 

 tion with the granite, and that it is composed almost wholly of granitic 

 debris. Some of the pebbles are large and well rounded, and the mass 

 seems to lie directly upon the rocks from which it was derived. An 

 unsuccessful attempt has been made to use this material for the bases 

 of gravestones. 



Between Cliftondale station and the Newbury port turnpike there is 

 quite a large area of conglomerate containing a considerable proportion 

 of quartzite pebbles. A smaller area of finer material occurs near the 

 end of Granite Street, by the spring, about a third of a mile north of 

 Maplewood. 



A most interesting and varied locality in which the stratification is 

 well marked may be found about a third of a mile southeast of Swain's 



