54 
TRANSACTIONS OF THE TEXAS ACADEMY OF SCIENCE. 
in their journey to the gulf. These are therefore the largest rivers, their 
valleys are the most extensive, and their soils the richest in the State. 
The “ red rises” of these rivers, from the rains which fall in the area of 
their headwaters, add a considerable amount of most fertile soil to their 
bottom lands yearly. 
Red River in the eastern part of its course has in its first bottom deep 
red sandy or waxy soils, heavily timbered with cottonwood, elm, ash, 
walnut, pecan, etc. Bej'ond this the second bottoms of sandy loam ex¬ 
tend back to the bluffs. These bottoms are from one to two miles wide, 
and are succeeded by high rolling uplands. 
The Brazos in its course gulfward crosses the various formations almost 
at right angles to their strike, and encountering beds of very unequal 
hardness, is turned this way and that until its course is exceedingly tor¬ 
tuous. In places its valley is of considerable width, with bluff hillsides 
bordering it on either side, while at others the hills draw nearer and 
nearer together until the valley and the channel are nearly coextensive. 
In passing through the Grand Prairie the valley has a width of from 
five to eight miles, timbered with oak, pecan, etc. On reaching the 
softer materials of the Black Prairie the valley widens, and the first bot¬ 
tom occasionally attains a width of two miles, while the second bottom 
spreads five miles on either side of it. 
In the Tertiary plain its bottom lands are also wide, with a growth of 
large timber, oak, elm, ash, pecan, etc. In this area occurs a feature 
that is repeated in the Coast Prairies. In Robertson county the Brazos 
valley not only includes the river itself but that of the Little Brazos as 
well. In other words the latter occupies a portion of a former channel 
of the river. The same is true of Cane} r creek, in Brazoria county. 
Of all our alluvial soils those of this river are considered the most 
valuable, both for fertility and endurance. It is the largest body in the 
State, and will compare favorably with the richest alluvial land in the 
world. The valley has a length of about 300 miles and its average width 
in this distance is four miles or more. In the upper portion the soil of 
the first bottom is a red or chocolate loam and that of the second bottom 
a dark sandy loam. The principal soil throughout its whole length is this 
red or chocolate loam, which occurs in belts from one-half mile to a mile 
or more in width. On account of its perfect drainage and great fertility 
it is most highly regarded. In the southern portion of the valley cane- 
brakes, a dense timber growth and bowers of grape vines almost cover 
the land, and it shows no diminution of fertility after being under culti¬ 
vation for fifty years. The black peach soil, so called from its abundant 
growth of wild peach, is also easily tilled and is especially adapted for 
sugar cane. 
The Colorado river, between the mouth of the Concho and Austin, has 
