G. K. Gilbert—The Colorado Plateau Province. Re 
Mountain building by displacement; Mountain building by 
eruption; Stratigraphy; and Erosion; and will be discussed 
under these heads, in the order indicated.* 
Their entire phenomena may be comprehended, measured, de- 
daiineatedi The course of many a fault can be 
the axis. There is in nature 
a third type, which involves 
a dip in only one direction. ; 
This is the monoclinal fold. It is a double flexure, connecting 
Strata at one level with the same strata at another level. In 
figure 1, the curvature between aa and 6) is a monoclinal fold. 
* The writer travelled, during three summers, with field parties of the Survey 
in charge of Lieut. M. Wheeler of the U. S. Engineers, and during « fourth 
with a field party of the Survey in charge of Major J. W. Powell. His reports to 
Lieut. Wheeler are published in the third volume of the re of “Explorations 
and Surveys west of the 100th ian.’ own observations, the c 
m which he has derived the material are: 1. The ob- 
Servations of Major J. W. P. publi his the “ Exploration of 
. W. in hi rt on 
the Colorado River of the West and its sues” and. in part unpublished. 2 
3. The observations of Mr. E. E. Howell andof the late Mr. A. R. Marvine, 
published in vol. iii, of Lieut. Wheeler’s Reports, and in part unpublished. 4. The 
observations of Dr. J. S. Newberry, published in Ives’ ‘‘ Explorations of the Colo- 
rado,” and in part unpublished. 5. The writings of Mr. Clarence King, “ Fortieth 
Farallel Survey,” vol. ii. 6. Mr. T. B. Comstock’s report in the U. 8. Engineers 
Lieut. Wheeler, published in the U. 8. Engineer report for 1875. 
