134 CONTRIBUTIONS TO THE GEOLOGY OF MAINE. [bull.k 
arc exposed along the stream for about a quarter of a mile and sho^ 
sandstones interbedded with slates, both having a uniform positio 
with strike N. 80° E., dip W. < 50°. The sandstone is dark graj 
fine grained, and uniform in texture, never approaching a conglomei 
ate. Where fresh it presents a crystalline appearance much lik 
quartzite. This is more particularly applicable to the Edmunds Hi] 
sandstone. 
Interbedded with these gray sandstones are thin beds of soft, yel 
lowish, micaceous shales, which are often nodular and flaky, with irreg- 
ular bedding. Embedded in this shaly layer on the side next th« 
sandstone is a solid mat of fossils — mostly brachiopods and lamelli 
branchs — together with many plant impressions and occasionally car 
bonized remnants of vegetable forms. With the fossils, or embeddec 
alone in the edge of the sandstone, are pebbles of slate and of limestone 
at times 2 inches or more in length. These facts indicate that the 
Chapman sandstone was formed on a beach which was probably washec 
by tides or currents and overhung by cliffs composed of calcareous 
materials. 
Under the microscope the rock is seen to contain quartz, feldspar, 
and fragments of sedimentary material. The quartz constitutes three- 
fourths of the slide and occurs as rounded and angular grains, rarely 
interlocking and embayed, and often with dust inclusions. Feldspar 
crystals are few and usually are not well preserved. The rock frag- 
ments present are nearly all long, oval pieces of slate, and no 
undoubted igneous material was found. There are a few grains of 
garnet and zircon, and much stringy micaceous and chloritoid mate- 
rial, which, mixed with quartz and calcite, forms the cement. 
MARS HILL CONGLOMERATE. 
Mars Hill is the most prominent landmark on the international 
boundary. All about the mountain and up to its very base the ordi- 
nary slated limestones of the region form a rolling plain about 500 feet 
above sea level. Above this the mountain rises to a total height of 
1,695 feet above tide, as measured by the aneroid, and covers an area 
about 2i miles long and half a mile wide. It is densely forested except 
at two localities on the southwest corner and a partly cleared area at 
the north end. This makes a final determination of structure and 
composition impossible at present. 
The mountain seems to have been first visited for geologic purposes 
in 1838, when Mr. Hodge, of Dr. Jackson's party, found here and there 
"outcropping ledges which proved on examination to be grauwacke, 
exactly like that on Sugar Loaf Mountain, and like that rock belong- 
ing to the regular Anthracite Coal Measures." * Hitchcock 2 refers to 
1 Jackson, Second Ann. Rept. Geol. Public Lands, 1838, p. 46. 
2 Agriculture and Geology of Maine, 1861, p. 386. 
