STR UCTURE OF THE MO UNT WA SUING TON MA SS. 727 



hedra) over a centimetre in diameter, and staurolites (usually 

 inclined-cross twins) a centimetre or more in length. Tourma- 

 line occurs only in minute crystals, much less widely distributed 

 than any of the other metamorphic minerals "except ottrelite. 

 Some of the localities where macroscopic garnets and staurolites 

 were found in the rock have been indicated on the map — small 

 black circles and crosses standing for the two minerals respec- 

 tive^. 



(c) Egremont Limestone. — This horizon as developed in the 

 valley near the base of the mountain, is a white to gray crystal- 

 line limestone, which is often quite pure but for small scales of 

 colorless mica and grains of pyrite. Locally it contains thin 

 quartzitic or schistose layers. Generally it passes upward into 

 the Everett Schist of the flanks of the mountain through a graph- 

 itic layer of variable thickness, and a similar graphitic rock is 

 also to be found at its lower contact with the Riga Schist. As 

 met with in the summit plains, the limestone appears under two 

 modifications which grade insensibly into one another. They 

 are (1) a very micaceous limestone or calcareous mica schist; 

 and (2) a graphite schist, often, though not always, calcareous. 

 The first mentioned modification is to be found only in the cen- 

 tral portions of the northern summit plain, where the larger 

 streams have cut through the thick drift deposits. It is richest 

 in calcite at two localities, one of which is in the bed of Wright 

 Brook about midway between its confluence with Ashley Hill 

 Brook and the north and south road to the east, and the other is 

 in the bed of City Brook. This rock also occurs in the small 

 brook near the house of H. F. Keith, in the bed of Huckleberry 

 Brook, and at several localities on the Ashley Hill road between 

 Huckleberry and Wright Brooks. It always contains a silvery 

 mica, graphite and pyrite. 



In the northern summit plain graphitic schist (here generally 

 calcareous) forms a border separating the micaceous limestone 

 from the Everett Schist which surrounds it. According as it 

 occurs nearer the limestone, it is the more calcareous. In the 

 lower course of Wright Brook it contains layers of calcite over a 



