58 KANSAS ACADEMY OF SCIENCE. 



Hancock county, Ohio, and other places, the work done by means of natural gas is 

 enormous, and is increasing. This gas, like petroleum or rock oil, comes from the 

 bowels of the earth. It may be properly named rock gas. It is obtained from drilled 

 wells, some of which are over three thousand feet in depth. The strata which yield 

 the gas are more or less porous, like those which yield the rock oil. They are 

 mostly sandstones, and as the oil beds are known as " oil sands," so those which yield 

 gas are known as "gas sands." The porous sandstones, some of which are coarse- 

 grained, are not the sources but only the reservoirs of the fluids they contain. The 

 source is the decomposition of organic matter — mainly vegetable — with which cer- 

 tain other formations are charged to a greater or less extent. These other formations 

 are the dark-colored shales, and the so-called "black slate," and the seams of coal, 

 which under the conditions of their deposit and existence, including the enormous 

 pressure of hundreds or thousands of feet of superincumbent rocks, give out their 

 fluids — water, oil, and gas — to the porous beds above or below them. Gas and oil 

 are, as would be expected, often in a porous rock above the shale-bed source. Water 

 is always as low as it can get. The water mostly associated with oil and gas is salt 

 water. Oil wells usually have some gas; gas and brine wells have some oil. 



The term "gas sand" is used so commonly that it has become the equivalent of 

 the more general term "gas rock," and as such has been used where the containing 

 bed is not sandstone but limestone. In Ohio the Trenton limestone of the Lower 

 Silurian age has at a depth of 1,200 feet yielded gas and oil. If the rock is porous 

 and has an impervious covering of clay-shale or clay, it will hold these fluids. The 

 writer has treated a small piece of compact Permian limestone thus: It was dried 

 about to what it would be by outdoor exposure in dry weather. After carefully 

 weighing it, it was immersed for twenty-four hours in coal oil — the ordinary lamp 

 oil of commerce. Taken out, it was allowed to drain for an hour, and the wetness 

 was all wiped off. It was then carefully re-weighed. The result was as follows: 

 Weight before immersion, 103.5 drams. 

 Weight after immersion, 104.5 drams. 



This shows a quantity of oil absorbed in one day under ordinary atmospheric 

 pressure, amounting to nearly one per cent, of the total weight of the stone. The 

 writer has seen both sandstones and limestones much more highly charged with oil 

 than this. When an impervious covering is over such porous rock, and hundreds or 

 thousands of feet of superincumbent rock formations give their enormous pressure 

 to force the gas or oil into the rock pores as fast as it is formed in nature's labora- 

 tory, such porous rocks become vast storehouses of these valuable fuels. As we have 

 said, the two fluids are usually found together, though one or the other may prepon- 

 derate to such a degree as to cause the other to be but slightly regarded. But we 

 shall now speak more definitely of rock gas. 



The geological horizons at which rock gas has been found in Pennsylvania, West 

 Virginia and Ohio are in the Lower Coal Measures, and thence downward to the Lower 

 Silurian. The upper horizons are below the Pittsburgh Coal; an important inter- 

 mediate horizon is the Berea Grit, in the Waverley Series, and the lowest is the 

 Trenton Limestone. 



The force of the gas when the drill of the prospecter has tapped the porous res- 

 ervoir is sometimes such as to throw out the heavy tools used, and when ignited, to 

 send a flame forty feet high. The pressures measured, and estimated where meas- 

 urement was impossible, show the equivalents of from fifteen to fifty atmospheres. 

 These great pressures have caused much waste of gas, much leakage from pipe joints, 

 and consequent danger from explosions. On the other hand, the great pressures 

 have made it possible to pipe the gas to great distances, and the danger has stimu- 

 lated invention, so that perfectly tight joints are now made. Pittsburgh receives 



