STR UCTURE OF THE MO UNT WA SHING TON MA SS. 725 



relations in the vicinity of the mountain are set forth on 

 Plate III. 



Horizons Represented. — The Mt. Washington series thus con- 

 sists, not of two members as supposed by Dana, but of four, two 

 of which are calcareous. The calcareous beds alternate with the 

 schists, which have been shown to possess marked lithological 

 differences. The sequence of these beds is as follows : (a) a cal- 

 careous horizon which I designate the Canaan Dolomite from its 

 typical development at Canaan ; (b) the lower schist bed, which 

 I call the Riga Schist from Mt. Riga peak where it is perhaps 

 most typically developed ; (c) a calcareous horizon, which I 

 designate the Egremont Limestone from its wide extent in the 

 Egremont valley (this limestone is much modified in all locali- 

 ties above the valley floor) ; and (d) the upper schist horizon, 

 to which I give the name Everett Schist since it assumes its max- 

 imum thickness within the area at Mt. Everett. It will be noticed 

 that this sequence corresponds with that which Dale has deter- 

 mined for the Greylock mass in northern Berkshire county. 1 

 Below are given in parallel columns for comparison the series of 

 Mt. Washington and Greylock : 

 Mt. Washington Series. Greylock Series (Da/e). 



1. Canaan Dolomite. 1. Stockbridge Limestone. 



2. Riga Schist. 2. Berkshire Schist. 



3. Egremont Limestone. 3. Bellows Pipe Limestone. 



4. Everett Schist. 4. Greylock Schist. 



These beds are probably Ordovician though the lower portion 

 of the Canaan Dolomite may, like the Stockbridge Limestone, be 

 Cambrian. 2 No fossils have as yet been found in the vicinity and 

 it is hoped that further search may reveal them. Walcott 3 has 



'The Greylock Synclinorium, by T. Nelson Dale. Amer. Geologist, July, 1891, 

 pp. 1-7. Also given in detail in a forthcoming monograph of the U. S. Geological 

 Survey, by Professor Raphael Pumpelly. 



2 On the Lower Cambrian Age of the Stockbridge Limestone, by J. Eliot Wolff, 

 Bull. Geol. Soc. Am., vol. ii. 1891. See also Dale, ibid., vol. iii, pp. 514-519. 



3 The Taconic System of Emmons, and the use of the Name Taconic in Geolog- 

 ical Nomenclature, byCHAS. D. Walcott, Am. Jour. Sci., vol. xxxv, pp. 237-242, 399- 

 401, March and May, 1888. (With map). 



