11 
LITERATURE. 1 7 
"k a series of miniature anticlinoria and synclinoria, often with pitch- 
ing axes and generally with a north-northeast trend, and also, in 
^art, to irregular accumulations of drift. An exceptional case of 
differential erosion was observed in Poultney, where a basic dike 
forms the bottom of a small canyon, 50 to 100 feet deep, cut in 
slate. The hard dike rock has been eroded more rapidly than the 
softer slate. a 
In 1900 the writer described a small pyramidal mass of conglom- 
erate lying on the more erodible schists of the Taconic Range in 
Oastleton, Vt., and called Bird Mountain. Its form was attributed 
to its synclinal structure, relative hardness, vertical jointing, and 
erosion. In the same paper a schist cliff on Mount Herrick, in Ira, 
Vt., was noted, in which erosion could be seen at work undermining a 
forest. 6 
In 1002 the writer described some contacts between the pre- 
Cambrian and Cambrian on the Green Mountain Range, in which the 
strike of the pre-Cambrian gneisses indicated that the original trend 
of the pre-Cambrian folds, and consequently of the pre-Cambrian 
topography, may have been at right angles to that of the present 
range. 
In the same year H. F. Cleland described the recent denudation of 
the steep east face of Mount Grey lock/' 
The works listed below contain the most important expositions of 
the general physiographic principles involved in the following 
discussion. 
Works containing expositions of general physiographic principles. 
Dana (J. D. ). On denudation in the Pacific, [and] On the degradation of the 
rocks of New South Wales and formation of valleys. [Extracts from report 
on geology for Wilkes U. S. Explor. Exp. Philadelphia, 1840.] 
In Am. Jour. Sci., 2d ser.. vol. 0, pp. 48-02. 289-204. New Haven, 1850. 
Lesley (J. P.). Topography as a science. 
In Manual of coal and its topography, illustrated by original drawings, chiefly 
of facts in the geology of the Appalachian region of the United States of 
North America, pp. 121-187. Philadelphia, 1856. 
Rogers (H. D.). Orography and scenery; features of erosion in anticlinal 
belts; features of erosion in synclinal belts; features of local erosion; addi- 
tional illustrations. 
In Geology of Pennsylvania, vol. 1. pp. 4-30; vol. 2 (pt. 2), pp. 021-041, 1023- 
1024. Philadelphia. 1858. 
" The slate belt of eastern New York and western Vermont : Nineteenth Ann. Rept. 
T. S. Geol. Survey, pt. 3, 1800, pp. 175. 222. 207. pis. xii. xiii. 
ft A study of Bird Mountain, Vermont: Twentieth Ann. Rept. U. S. Geol. Survey, pt. 2, 
1000, pp. 15, 16, 10. 23. 
c Structural details in the Green Mountain region and in eastern New York (second 
paper) : Bull. U. S. Geol. Survey No. 105, 1002, p. 20. 
d The landslides of Mount Greylock and Briggsville, Massachusetts : Jour. Geol., vol. 10, 
1902, pp. 513-517. 
Bull. 272—05 m 2 
