724 THE JOURNAL OF GEOLOGY. 



reous horizon occupying the central Mt. Washington plateau, and 

 the locating of its boundaries (cf. map). Observations were 

 then made a little to the north of Salisbury village which showed 

 conclusively that the schist of that vicinity is below the limestone, 

 the structure of the mountain at that latitude being essentially 

 an anticlinal. On examining next the northern extremity of the 

 mountain, observations were quite as conclusive in proving that 

 the schist of Jug End is above the valley limestone, and that the 

 section across the -range at this latitude is essentially what Pro- 

 fessor Dana has described. This knowledge that we have to do 

 with two horizons of schist, the one lower and the other higher 

 than the limestone of the Egremont valley, was soon followed by 

 the discovery of lithological differences between the different 

 beds, which have furnished the key to the structure. Topograph- 

 ical features soon suggested a course across the mountain through 

 which the limestone might pass and separate the upper schist of 

 the northern portion from the lower schist of the southern por- 

 tion. Through this path the calcareous horizon of the Egremont 

 valley, considerably modified it is true, has been carefully traced. 

 A large number of observations have been gathered from all parts 

 of the mountain mass. Each of the numerous peaks has been 

 ascended and as many data as practicable have been collected. At 

 this time the southern portion of the mountain had not been 

 carefully studied. Later in studying the area lying to the east 

 and southeast of the mass of Mt. Washington, it was found that 

 the limestone of that section is divisible into two beds separated 

 by a schist, which is lithologically identical with the lower of the 

 two horizons of schist in Mt. Washington. The evidence sup- 

 porting this and the manner in which the areal relations are illu- 

 sive in the indications which they afford regarding stratigraphy, 

 will be set forth in a later paper. The lower of the two lime- 

 stone horizons was found to extend westward and disappear under 

 the schist of the south end of Mt. Washington. The schist over- 

 lying it,. which so resembled the lower of the Mt. Washington 

 schists, was also traced along the northern border of the lime- 

 stone into the southern portion of Mt. Washington. The areal 



