18 TACONIC PHYSIOGRAPHY. 
Powell (J. W.). On the physical features of the valley of the Colorado. 
In Exploration of the Colorado River of the West and its tributaries, explored 
in 18(59, 1870, 1871, and 1872, under the direction of the Secretary of the 
Smithsonian Institution, pp. 149-214. Washington, 1875. 
Gilbekt (G. K.). Land sculpture. 
In Report on the geology of the Henry Mountains, pp. 99-150. Washington, > 
1877. 
Dutton (C. E. ). Tertiary history of the Grand Canyon district. 
In Monograph U. S. Geol. Survey, vol. 2. With atlas. Washington, 1882. 
Lowl (F.). tther Thalbildung. Prague, 1884. 
Richthofen (F. von). Einfliisse auf die Erosion welche in der Lagerung unci 
Beschaffenheit des Gesteins beruhen ; die tektonische Thaler ; Sculptur- 
thaler : Faltungsgebirge ; Abraisionsgebirge. 
In Fiihrer fur Forschungsreisende. pp. 158-177, G39-045, 645-051, 660-009,' 
009-070. Berlin, 1880. Second edition, 1901. 
Noe (G. de la) and Margerie (E. de). Des causes determinant le trace des^ 
cours d'eau. 
In Les formes du terrain, pp. 113-178. Paris, 1888. Service geographique de 
l'armee. 
Penck (A.). Die Thaler; die Thallandschaften : die Faltungsgebirge. 
In Morphologie der Erdobertiache, pt. 2, pp. 58-141, 142-203, 370-408. Stuttii 
gart, 1894. 
II 
D 
fl 
Readers unfamiliar with the subject of physiography are referred 
to the following elementary works: 
Elementary works <>it physiography. 
Merrill (G. P.). The principles of rock weathering. 
In Journal of Geology, vol. 4, pp. 702-724, 850-871. Chicago. 1896. 
Geikie (.1.). Land forms in regions of highly folded and disturbed strata.: 
In Earth sculpture, or the origin of land forms, pp. 73-119. London, 1898. 
Davis (W. M.). Physical geography. Boston, 1898. 
See, especially, chapters 7, 9, and 10. 
Gilbert (G. K.) and Brigham (A. P.). An introduction to physical geography. 
New York, 1902. 
IjANB form. 
In the northwestern part of the area represented on the map (PL 
I), at an elevation of 101 feet above sea level, lies the southern end of 
Lake Champlain, and 32 miles south-southwest of it is a portion of the 
Hudson which, between the mouth of the Batten Kill and Troy, falls 
from the 100-foot to below 7 the 20- foot level. The highest points in 
the area are Mounts Greylock, 3,505 feet; Glastenbury, on the Greem 
Mountain Range, 3,764 feet; Equinox, 3,816 feet, and Dorset, 3,804 
feet. The map shows the forms of the surface in white and four 
tints, corresponding to elevations below 800, between 800 and 1,500, 
1,500 and 2,000, 2,000 and 2,500, and 2,500 and 3,816 feet. 
Green Mountain Range. — That portion of the Green Mountain 
Range which extends northward from the southeast corner of the 
