66 GUIDEBOOK OF THE WESTERN UNITED STATES. 
down in the sea, and as these rocks are widely distributed through 
the United States and Canada the sea must have covered most of 
the continent, or at least a wide area extending from north to south. 
It certainly extended eastward into Iowa and westward as far as 
the Wasatch Mountains. The Rocky Mountains were not then in 
existence, for this region was occupied by a shallow sea in which 
animal life swarmed, much as it does in the warm, shallow seas of 
to-day, and many of these forms were covered with mud and almost 
perfectly preserved. 
About three-quarters of a mile beybritl milepost 132 Turkey Creek 
enters the valley from the north (right). Up this creek there are 
extensive sandstone quarries from which much stone 
has been taken for constructing buildings at Pueblo. 
The quarries are connected with Pueblo by a branch 
railroad. At Swallows the Denver & Rio Grande 
Western crosses to the north side of Arkansas River and about a mile 
farther on it passes under the Santa Fe, which a short distance be- 
yond crosses to the south side of the stream. 
West of milepost 142 the railroad crosses Beaver Creek, a large 
stream that joins the Arkansas from the north, and a little farther 
on is the station of Beaver. A short distance to the northwest is 
Beaver Park, which is noted for its apples, cherries, 
and small fruits. The land is irrigated from Beaver 
Creek, which derives its supply of water from the 
mountains on the north. At Beaver most of the 
formations already described or mentioned have disappeared, and 
the Pierre shale lies at the surface. The Niobrara formation rises 
again farther west, and at the towns of Cement and 
Portland it is used extensively in the manufacture 
of Portland cement.*° The first cement mill to be 
seen is that of the United States Portland Cement 
Co. on the north (right) of the railroad, and a mile 
farther on, at Portland, the Colorado Portland Cement Co. has an 
extensive plant on the south side of the track. 
A short distance beyond milepost 147 the Denver & Rio Grande 
Western crosses the Arkansas and remains on its south side for 8 
miles. West of Portland the rocks dip gently toward the west, 
Swallows. 
Elevation 4,887 feet. 
Denver 135 miles. 
Beaver. 
Elevation 4,996 feet. 
Denver 143 miles. 
Portland. 
Rlevation 5,051 feet. 
Population 473. 
Denver 146 miles, 
* Portland cement is an artificial ; materials, provided the mixture has 
product consisting of 60 to 65 per cent 
of lime, 20 to 25 per cent of silica, and 
5 to 12 per cent of oxide of iron and 
alumina, and it has the useful property 
of hardening or “ setting” under water. 
It is obvious that Portland cement may 
manufactured from a variety of raw 
the chemical composition noted above. 
The most successful plants, however, 
are those which obtain all the neces- 
raw materials from the same 
quarry. Thus, limestone is needed for 
the lime and a sandy shale for the 
silica, iron, and alumina, but com- 
