728 THE JOURNAL OF GEOLOGY. 



centimetre in thickness, while on the road encircling the west 

 flank of Mt. Everett it hardly effervesces at all with acid. At 

 localities south of the central plain the rock only rarely exhibits 

 effervescence with acid. The graphite schist differs from the 

 limestone not only in the large proportion of graphite and the 

 correspondingly small amount of calcite which compose it, but 

 its least calcareous varieties contain also much feldspar and quartz. 

 Garnets and tourmaline have each been found in one specimen, 

 the first near the lower, and the second near the upper schist con- 

 tact. 



(d) Everett Schist.- — The rock of this horizon is not in all 

 cases to be easily distinguished from the Riga Schist. Like that 

 rock it is porphyritic from lenticular feldspar grains, but these 

 feldspars are much more abundant and more constant, and the 

 base is generally more chloritic or sericitic. Ottrelite is found 

 sparingly at some localities. The most striking lithological dif- 

 ference from the Riga Schist, however, exists in the entire absence 

 of macroscopic garnets and staurolites from this horizon, not an 

 individual of either species having been found within the entire 

 length and breadth of the area of this horizon exposed, though 

 they have been carefully sought at each locality. The beds 

 seem to become more sericitic along the northwestern foot of the 

 mountain. A phase of the rock which is more characteristic of 

 the southeastern portions of the area is very chloritic with mag- 

 netite octahedra sometimes as large a pea. Chloritic phases of 

 the rock also appear in the extreme northern areas. 



Explanation of Map, Areal Geology. T — The eastern and south- 

 ern portions of the map are based on the Sheffield and Cornwall 

 sheets of the topographical map of Massachusetts and Connecti- 

 cut by the U. S Geological Survey, and the portion of the map 

 lying in New York State is compiled from older road maps. The 

 manner in which the Egremont Limestone crosses the mountain 

 separating the Everett and Riga Schist horizons, may well be 

 emphasized by special description. On the eastern side the 

 course of the calcareous horizon as it gains the summit plain is 



'See Plate III. 



