ABSTRACT OF THE MONOGRAPH. 
3 
monocline on the other. The Paria Plateau is situated at a lower level 
than the others. East of the latter we come upon the margins of the 
Mesozoic formations, which wall the Grand Canon district upon the eastern 
side and present their broken edges towards it in the Echo Clilfs. 
Chapter II gives an account of the Terraces and the strata which they 
disclose. It also points out the extension of those strata westward and 
southwestward into the sierra country of southern Nevada, where they 
assume a littoral character around the Mesozoic mainland, whence their 
materials were derived. This mainland occupied what is now the site of 
the Great Basin of Nevada and western Utah. The extensions of the 
Mesozoic system along the eastern side of the Grand Canon district are 
also pointed out. They reach far south into the heart of Arizona and 
beyond the limits of observation. The edges of the Mesozoic system are 
found encompassing about two-thirds of the periphery of the district. The 
remaining part of the circuit now appears to have been the locus of a shore- 
line. The peculiarities of the cliflPs of the terraces are also described and 
the drainage system is explained. 
Chapter III is mainly devoted to a description of the Vermilion Clilfs 
which bound the Triassic terrace. It is written in effusive style, and is an 
attempt to portray the magnificent scenery which this colossal wall presents. 
Its grandeur culminates in the Valley of the Virgen, which is not only of 
great proportions, but is remarkable and even unrivaled for the beauty and 
coloring of its rock temples. There is added to this chapter a description 
of the lowest or Permian terrace. 
Chapter IV is devoted to the inference that the Permian, Mesozoic, 
and Tertiary formations, now ending cliff-wise in the terraces, once ex- 
tended over the entire expanse of the Carboniferous platform of the Grand 
Canon district. During Tertiary time they were denuded, and the total 
thickness of strata thus swept away, though varying somewhat and per- 
haps notably in different places, averaged probably about 9,000 feet. The 
evidences upon which this conclusion rests are discussed at some length 
and carefully criticised, and the conclusion is believed to be well sustained 
by the evidence. 
The argument for the conclusions reached is mainly derived from the 
