14 OIL FIELDS OF TEXAS-LOUISIANA COASTAL PLAIN, [bull. 212. 
Galveston counties, Tex., there are pronounced elevations, of a few 
hundred acres in extent, rising to heights of from -10 to 50 feet above 
the level of the coast marshes. 
Bordering the marsh along its northern edge is a second belt, largely 
prairie land, whose surface rises gradually toward the northwest, at 
an average rate of from 10 inches to a foot per mile. 
A few small prominences appear within this belt, as at Spindle top 
and Fairchild Hill, in Jefferson County; at Sour Lake, Dayton, Bar- 
ber Hill, Kiser Mound, near Columbia, and Damon Mound, in Brazoria 
County; and the Sun Mounds, in Waller County. These, however, 
do not present any great elevations, Damon Mound, probably the 
highest, having a maximum of 83 feet above the plain, or probably 
not more than 140 feet above the Gulf. 
The third or inner belt of country belonging to the Coastal Plain 
rises comparatively rapidly from the second, and has a more broken 
and generally timbered surface, with numerous small rounded hills. 
The general elevation of this belt does not appear to exceed 175 to 
200 feet above sea level. 
DRAINAGE. 
In the eastern part of the region throughout Louisiana the rivers 
are deep and sluggish. The few streams of any magnitude are the 
Vermilion Bayou, Bayou Nenienfou, and Calcasieu River. Each of 
these streams is narrow, deep, and clear, has scarcely any appreciable 
current, tends to expand into a broad, shallow lake, and enters the 
Gulf through a shallow bay. Vermilion River flows into Vermilion 
Bay. The Nementou shortly after the junction of Bayou Nezpique 
and des Cannes expands into the broad, shallow Grand Lake, with a 
depth of little over 3 feet, and again contracts only to enter the Gulf 
through a wide month. The Calcasieu forms a series of shallow 
lakes such as Calcasieu, Black, and West Lake, extending all the 
way from Lake Charles to the>coast. These Louisiana rivers all have 
the peculiar characteristics of drowned or submerged streams. 
Throughout the Coastal Plain in southeast Texas the streams are 
similar in character to those in Louisiana. The Sabine and Neches 
unite to form Sabine Lake; the Trinity debouches into the eastern 
end of Galveston Bay; the Colorado reaches the Gulf through Mata- 
gorda Bay, and the Nueces Hows into Corpus Christi Lay. Of all the 
rivers in this area the Brazos alone enters the Gulf directly and with- 
out the intervention of any lagoon or bay. 
West of the Nueces the coast drainage fails almost absolutely, as 
the whole stretch of coast line to the Rio Grande contains only two 
small creeks, the San Fernando and the Olmos, and these unite to 
form Copano Bay, near the head of Laguna de la Madre. 
These streams of the Gulf Coastal Plain may be divided into two 
groups — an older, pre-Pleistocene or pre-Columbia, and a younger, 
