144 OIL FIELDS OF TEXAS-LOUISIANA COASTAL PLAIN, [bull.212. 
and also in Spindletop, has never been satisfactorily explained. For 
a variety of reasons it does not seem possible that they can be the result 
of evaporation of sea water in natural salt pans, which is supposed to 
be the origin of most deposits of rock salt. It may therefore be 
necessary to refer their origin to supersaturated solutions coming from 
the lower strata through fissures opened along a fault line. If such 
fissures were open to the surface, as Hill suggests, any petroleum 
brought up from the lower beds by the ascending waters would 
escape. If the vent were subsequently sealed up by the deposition 
of impervious beds, the fissure might remain open and afford a means 
for the oil to be collected and brought up by the slow circulation of 
water under the influence of convection currents. It is suggested, 
as a possible explanation of the difference between Spindletop and 
Sour Lake on the one hand and Damon Mound and the Louisiana 
Salt Islands on the other, that the former vents were effectually 
sealed up after the salt had been deposited, while the latter have always 
remained open; the oil, which subsequently followed the same course 
taken by the salt solution, was in the former checked before reach- 
ing the surface, while in the latter it reached the surface and practi- 
cally all escaped. 
STRUCTURAL CONDITIONS. 
It is suggested above that the location of the oil pools in the Gulf 
Coastal Plain is determined by certain structural features, namely, 
dislocations of the strata in the form either of faults or of anticlinal 
flexures. A study of the distribution of the localities at which gas, oil, 
and salt are known to occur in the Coastal Plain affords some support 
to this theory and also suggests the districts where prospecting may 
be carried on with the best chances of success. It will be observed 
from the accompanying map (PI. VII) that the known deposits of these 
associated substances occur along northeast-southwest lines. Five 
such lines of deposits are shown, all but one being determined by 
at least three points. The westernmost line contains Saratoga, Day- 
ton, and Damon; the second contains Sour Lake, Barber Hill, Kiser 
Hill or Columbia, and Big Hill, Matagorda County; the third con- 
tains Spindletop, Big Hill, Jefferson County, High Island, and prob- 
ably Bryan Heights; the fourth contains Sulphur, Vinton, and Sabine 
Pass; and the fifth, Spring Hill and Hackberry. Other points in 
Louisiana do not appear to observe this linear arrangement, although 
further investigation of this region may extend the system to include 
these as well as the famous Salt Islands. 
It is of interest to note that these lines are almost exactly parallel 
to the most prominent structural feature in the entire Texas region, 
namely, the Balcones fault, which has been described by Hill as pass- 
ing through the center of the State. Further confirmation of the sig- 
nificance of these lines is afforded by the work of Veatch in the salines 
