444 GEOLOGY OF NORTHWESTERN TEXAS. 



who would be able to tell the geological formation through which the drill 

 was passing by the material brought up by the augur, otherwise the desired 

 practical results might not be obtained. 



What is here said of Dallas would apply with equal force to any other lo- 

 cality in the Cretaceous area except as to depth. At Dallas the Cretaceous 

 is about one thousand feet thick, while at Waco it is two thousand and at 

 Fort Worth probably about eight hundred. 



The following is a list of wells, their locality and depth, where natural 

 gas has been found in the Carboniferous strata in Texas. 



Locality. 



Gordon 



Thurber 



Canyon 



Dalton 



Trickham , 



Waldrip 



San Angelo 



Fish Creek, Young County. 

 Belknap , 



No. 

 wells. 



Depth. 



310 feet. 

 480 feet. 

 500 feet. 

 384 feet. 

 100 feet. 



80 feet. 



80 feet. 

 120 feet. 

 800 feet. 



SALT. 



Common salt or chloride of sodium contains sixty per cent of chlorine and 

 forty per cent of sodium. The common article is very seldom free from 

 other minerals, such as calcium and magnesium. The material from which 

 salt is manufactured occurs as rock salt and saline water either in springs, 

 lakes, or wells. 



The origin of the material is much the same as gypsum, i. e., it is a pre- 

 cipitate from an enclosed sea. At present salt lakes and superficial accumu- 

 lations of salt occur in various parts of the world, and these have furnished 

 data for reasoning as to the saliferous deposits of earlier times. Salt lakes 

 are derived from salt springs and the remaining portion of water cut off from 

 the open sea, and when the evaporation of water occurs by the action of the 

 sun and winds only fresh water is taken up by the process of evaporation. 

 Now as water can only contain a certain amount of salt in solution, when 

 the process of evaporation has gone on until the water has decreased so that 

 it is completely saturated with salts, then as farther evaporation goes on the 

 salt will be precipitated to the bottom, and in time beds of rock salt are the 

 result. It often happens that during the process of evaporation water will 

 flow into the lakes either from the ocean or from inland sources, and the pro- 

 cess of the precipitation will be delayed for awhile, and beds of sand or clay 

 will be deposited on top of the salt already precipitated, and after awhile salt 

 will be again precipitated on the top of the clay or sand beds. As the result 

 we find beds of salt interstratified with beds of clay and sandstone. 



