EXDLicii.] ECONOMIC GEOLOGY PETROLEUM. 151 



From these analyses it appears that we have in solution mainly two 

 minerals : Halite (salt) and Thcnandite (sodium suljihate). A third one 

 is the Trona. Dr. Heizmaun mentions, in addition to these, lime and 

 magnesia. 



The predominance of sodium sulphate is an interesting feature, and 

 has a diiect bearing ui)on the genesis of these compounds. We are 

 aware of tlie fact that many of the shales and marls from which the 

 alkali is derived contain minute crystals or small seams of pyrite. Upon 

 the decomposition of both shales or marls and the i)yrite, the liberated 

 sulphur of the latter combines as sulphimc acid with the soda, or, in 

 some instances, magnesia, which has been set free from the shales. 

 Thus the substance which is found in the greatest quantities is formed. 

 Although magnesiiuu sulphate appears to occur but sparingly in the 

 region through Avhicli we traveled, it has been found elsewhere in large 

 deposits, which occupy positions analogous to those in which we observe 

 our " alkali Hats." 



petroleum:. 



Two localities were Aisited in our district where springs of petroleum 

 occiu". One spring is located on the Little Po])o-Agie. It is quite exten- 

 sive, and in the course of years has emitted a large quantity of oil. The 

 other one is situated near Camp Brown, and issues together with water. 

 No means Avere at hand either to test the oil on the spot or to carry it 

 with us. Therefore the only examination that could be made consisted 

 in the simple trial of burning it. Taking some of the hardened mate- 

 rial, we found that it burned with a bright tlame, and that nearly all of 

 it was consumed. I am not prepared to say that the composition of 

 this oil is identical with that occiuTiug in Pennsylvania, for instance, but 

 I am of the opinion that by distillation a product might be obtained 

 which vfould answer for the pui'i)0ses of illumination. In the course of 

 time these springs may prove to be valuable, as their location rendeis 

 them accessible to that portion of our district which offers the most 

 varied and the greatest inducements to settlers. 



