152 CONTRIBUTIONS TO THE GEOLOGY OF MAINE. [bull. 165. 
down the river, between the two large kersantite dikes, is a consider- 
able area occupied by an impure, partly crystalline limestone with 
lead color and conchoidal fracture. It gives the appearance of having 
been brecciated on a fine scale and recemented. The microscope shows 
its composition to be in the main calcite, quartz, and grossularite. A 
short distance below this outcrop the immediate effects of the dike 
intrusions disappear. 
The rocks adjoining the Mapleton granite are metamorphosed 
within a radius of about a mile to the southwest. The bedding 
of the original siliceous material is retained and can be easily traced 
for a considerable distance. The rock itself, however, has been 
converted into a tough, dense hornstone with conchoidal and splint- 
ery fracture. It is usually black, but at times it takes on a mottled 
gray color. In weathering a distinct white zone is produced, which 
is sharply marked off from the inside, as is common in felsitic 
rocks. The facts obtained from a microscopic examination show its 
metamorphic character and substantiate the observations made in the 
field. The sort of metamorphism here expressed and the general field 
relations lead to the conclusion that these hornstones are the unre- 
moved remnant of the granite cover which on Munson's farm has 
entirely disappeared. 
Drews Lake area. — The metamorphic rocks about Ludlow have not 
been studied in detail, but a few general observations may be made. 
Throughout the township of New Limerick metamorphic action has 
produced a hard schist marked by bands usually less than an inch 
wide which indicate the original bedding of the rock. The strike is 
several degrees more easterly than in the case of the less altered rocks 
to the north and east, and the dip is practically vertical. The banded 
appearance is produced, in the outcrops examined, by four layers: (1) 
a very hard, dark-blue, impure limestone, which sometimes attains a 
thickness of several feet; (2) a whitish siliceous limestone; (3) a hard- 
ened, black, micaceous slate; (4) a reddish layer of extremely fine, 
micaceous sandstone. This last layer is not very common. At Drews 
Lake more excessive local metamorphism has produced garnetiferous 
schists, and in one case a bed of saccharoidal limestone containing 
crystals of pyrite. The intrusion of many smaller dikes and the 
metamorphism caused by sharp folding of the calcareous strata still 
further complicate the structure in this region, and it is planned to 
devote more attention to it at another time. 
RHYOLITES. 
The rhyolites exhibited at Haystack, although covering so small a 
territory, exhibit great variation in composition and structure. 
