276 THE IRON ORE DISTRICT OF EAST TEXAS. 



"A consideration of the above figures shows in the first place that the 

 crude petroleum of Nacogdoches is practically free from naptha, which dis- 

 tills off below 250° F. Four pounds of this oil carried to a temperature fifty 

 degrees higher yielded only a few drops of a light oil, amounting to 0.04 per 

 cent of the total amount taken. In the Pennsylvania crude petroleum the 

 illuminating oil comes oft' between 250°. and 500° F., and 'it on an average 

 amounts to about fifty-five per cent. The Nacogdoches petroleum between 

 the same degrees of temperature yields only a little over seven per cent. 

 Three-fourths of the oil does not boil until a temperature above the boiling 

 point of mercury is reached. Above 400° F. and even lower the distillate is 

 not pure white, but is somewhat colored. This color deepens on exposure to 

 to the atmosphere. The distillate exhibits a beautiful fluorescence. Attempts 

 were made to render the distillates colorless by refining them with oil of 

 vitriol, etc., as is done with the ordinary petroleum, but the results obtained 

 were not satisfactory. Some of the crude oil was subjected to distillation 

 until but a small residue was left in the retort. This residue had the con- 

 sistency of thick pitch, and was of black color. 



"The density of the petroleum at 62.6° F., is 0.9179, compared with water 

 as unity. The density of Pennsylvania petroleum is usually about 0.794- 

 0.840. The coefficient of cubical expansion, as determined by Mr. Fitzhugh, 

 is 0.02568. Its weight, its high boiling point, its non-solidification by cold, 

 and its property of not gumming make it a splendid lubricating material. 

 The practical tests that have been applied to it confirm this opinion." 



GREENSAND MARLS. 



In the bed of the road from Nacogdoches to Melrose, about four miles north- 

 west of the latter, is an exposure of five feet of indurated greensand shell 

 marl, under which is four feet of very friable greensand shell marl. Under 

 this is a shaly marl two feet, with a middle parting of very hard indurated 

 green clay, two inches. Underlying this is a bed of altered greensand marl, 

 three feet. 



On Aaron's Hill, just west of the town of Nacogdoches, is an exposure of 

 greensand shell marl twenty feet thick. A lower portion of the same bed is 

 exposed at the crossing of Bayou Lamana, in the same road, on the west side 

 of the town of Nacogdoches. 



In the road bed on the hill just south of the brick yard, in the southern 

 limits of the town of Nacogdoches, is an exposure of several feet of green- 

 sand marl with fossil casts. (See Fig. 24.) South of Melrose, in the oil 

 regions along the valley of Bayou Visitadoi and its tributaries, is a large 

 deposit of oil bearing greensand marl. (See Map of the Oil Regions.) 



At the falls on the headwaters of Caney Branch, about one mile northeast 



