PHILLIPS. — COMPOSITION OF NATURAL GAS. 83 



pressure to which it is there subjected, it is probable that when a drill 

 taps the gas-beariug rock, causing relief of pressure, the more volatile 

 among the constituents of the liquefied gas would escape in relatively 

 laro-er proportion at the outset. The process occurring would be of the 

 nature of fractional distillation, and would tend to the production of a 

 gas especially rich in the most volatile constituent ; but the most volatile 

 constituent of natural gas is nitrogen, since all of the hydrocarbons and 

 carbon dioxide would be more readily liquefied than nitrogen. The first 

 yield of a gas well should therefore contain a higher proportion, relatively, 

 of nitrogen, and this nitrogen should gradually diminish as the liquefied 

 gas continued to evaporate. There would result after a time a gaseous 

 mixture containing less and less of nitrogen, and when the reduction of 

 pressure had progressed so far as to permit of the conversion of the 

 least volatile of the constituents into gas, the proportion of nitrogen in 

 the escaping gas would become constant, because the process would then 

 be one of outflow of a gas mixture, and not of volatilization of an 

 extremely low boiling liquid whose constituents have different boiling 

 points. 



If natural gas occurs liquefied in the rocks, we should expect to find that 

 the newly drilled wells yield at first a gas relatively richer in nitrogen. 

 The rock pressure in the Pennsylvania natural gas fields has in rare 

 instances attained to 1,000 pounds per square inch. Some cases are 

 reported in Northern New York State where rock pressures of 1,500 and 

 2,000 pounds have been measured. Such pressures are probably the 

 highest ever observed in any natural gas field, but such pressures would 

 be insufficient to liquefy natural gas. Should further determinations of 

 nitrogen furnish evidence that a gradual diminution of the percentage 

 of nitrogen is in progress, support would be given to the view that 

 natural gas occurs in liquefied form in the rocks. The great productive- 

 ness of many single wells is, upon this supposition, more readily ex- 

 plained, for in the interstices of the rock might be stored a much larger 

 quantity of gas if in liquefied form. The study of the composition of 

 natural gas will have much to do with determining this point. 



