116 
CONTRIBUTIONS TO THE GEOLOGY OF MAINE. 
[BULL. 165. 
tion of any observer because of the chunks of bright-red jasper 
included in it. It is at present impossible to locate these dikes accu- 
rately or to trace their boundaries, for the entire mountain side is 
overgrown with dense underbrush, which has grown up after burn- 
ing and cutting off the large trees, and which makes the discovery of 
outcrops a matter of chance. The other outcrops of diabase are easily 
found, and present no peculiarities in their method of occurrence. 
TESCHENITES. 
The massive dikes of this rock form the most conspicuous geologic 
feature of the southwest part of Mapleton Township (see fig. 5). 
Few continuous outcrops are seen, but the many small exposures 
Fig. 5. — Map of part of Mapleton Township, showing teschenite area. 
indicate a series of dikes in close proximity, extending about 1J miles, 
with a combined width of dikes and intervening slates of three-fourths 
of a mile. The places most favorable for study are on lots 100 and 
107, but lots 106 and 108 furnish good outcrops, and the southeast 
half of lot 99 is practically composed of a hill of this material. One 
mile east of Mapleton post-office a road leaves the section line and 
turns south, in order to avoid passing over a hill, and the blasting and 
digging required in cutting this road have given an excellent geologic 
section for a distance of about a quarter of a mile across the strike of 
the sedimentaries and the direction of the teschenite dikes. The 
exposures show the country rock in this vicinity to be an arenaceous 
shale baked, at the contact with the dike, into a gray siliceous slate. 
The dike itself outcrops along the road for 400 feet, with great varia- 
tion in appearance. All these rocks have been well preserved by the 
