138 DISCUSSION. [Feb. 5, 



With regard to the very full statement which we have had from 

 Prof. Mabery, I need only say that he has accomplished an immense 

 amount of work; and nobody except those who undertake fractional 

 distillation will understand anything of the enormous difficulty that 

 he has had in this work and the amount of labor he has put upon 

 it ; the results which he has already attained and published are, 

 in my opinion, far beyond the combined work of the several inves- 

 tigators who have previously published results on Pennsylvania oil 

 and American petroleum without specifying its origin, as in the 

 case of the two or three European investigators. 



Mr. Joseph Wharton : I should like to ask whether any gentle- 

 man here can throw any light as to the physical condition of natural 

 gas at the low depth at which it is found ; whether it exists as gas at 

 the depth of 2000 to 3000 feet, or whether it is condensed into a 

 liquid form at that depth. Is there any one here who has knowledge 

 upon that point ? 



Prof. Mabery: It seems probable that the gas should be lique- 

 fied under the great pressure to which it is subjected. That the 

 pressure is enormous we know. It depends somewhat, doubtless, 

 upon the structure that exists in those lower strata. Some very inter- 

 esting experiments have been made in studying those strata, and I 

 think it is probable from what is known that natural gas has existed 

 in the liquid form. 



Mr. Wharton : Does any one know what the critical point of 

 natural gas is ? 



Prof. Mabery : I should say it would depend largely on the 

 critical point of marsh gas. Liquefaction of this gas takes place 

 under 180 atmospheres at 11° degrees Centigrade. 



Mr. Wharton : Has there been any experiment as to artificial 

 liquefaction of natural gas ? 



Prof. Mabery : Yes; all those gases have been liquefied. 

 Prof. Peckham : The sulphur in petroleum may be derived from 

 two different sources : where there is a very small percentage, a 

 fraction of one per cent., it may be that the sulphur was a constitu- 

 ent of the original material from which the petroleum was produced ; 

 but where the sulphur content has arisen to several per cent., as is 

 often the case in the more dense liquid and solid bitumens, I think 

 the sulphur has been produced by a reaction between the material 

 of the bitumen itself, and salts — sulphates — in natural waters. It 

 seems hardly possible that from any source — any animal or vegeta- 



