HAYES AN 
KENNEDY 
^ D ] DRAINAGE AND TIMBER. 15 
post- Columbia. The pre- Columbia (and probably even pre-Lafayette) 
group includes the Sabine, Neches, Trinity, Brazos, Colorado, Gua- 
dalupe, and Nueces, all of which appear to have been in existence 
during Lafayette time. The younger, or post-Columbia, rivers are 
the Vermilion, Nementou, Calcasieu, San Jacinto, Buffalo, Clear, 
Oyster, San Bernard, Caney, Lavaca, Aransas, San Fernando, and 
Olmos. 
A glance at the map of the region (PL I) will show the reasons for 
this division. It will be noticed that all the rivers included in the 
■ older group pass completely across the Coastal Plain, heading upon 
the older formations of the interior, while the streams of the second 
or younger class are confined wholly to the plain itself, heading within 
it, or in the strong springs which rise from the Fayette sands at its 
northern border. 
Notwithstanding the large number of rivers which occur in the 
Coastal Plain, much of its surface is poorly drained. Water stands 
in many small lakes or ponds throughout the year, and over consid- 
erable areas the surface is largely under water during the wet season. 
The drainage of the country, particularly throughout the lower or 
coast portion, develops some peculiar anomalies. For instance, Mud 
Bayou, near High Island, begins within a mile of the Gulf shore, but 
follows a series of meanders north and west, and finally enters Gal- 
veston Bay about 2 miles north of the Gulf. 
TIMBER. 
Regarding the timber of the Coastal Plain it may be broadly stated 
that the cypress is confined to the eastern end, or to the swamps 
occurring within the immediate drainage area of the Mississippi 
River, very few of these trees occurring west of the Sabine River. 
The magnolia (M. grandiflora) is found in a belt stretching in a gen- 
eral southwestern direction through the parishes of Sabine and Ver- 
non, Louisiana, and the counties of Newton, Jasper, Hardin, Liberty, 
and San Jacinto, Texas, terminating in a few straggling trees in the 
neighborhood of Houston. The western end of the great southern 
belt of pine is reached near the Brazos River. West of the Brazos 
the tree growth is mostly represented by oaks and mesquite, the lat- 
ter gradually becoming the only timber to be found. 
GEOLOGY OF THE GULF COASTAL PLAIN. 
SUBDIVISIONS. 
Although in its main physiographic and geologic features the Gulf 
Coastal Plain is a unit, its eastern and western portions differ in some 
important particulars. The natural line of demarcation between the 
two divisions is the Guadalupe River. The most striking differences 
are climatic, but the character of the geologic formations also changes 
at this line. 
