1897.] PETROLEUM AND NATURAL GAS. 99 



has received a more definite statement. Engler distilled 490 

 kilos, of menhaden oil at a temperature beginning at 320° C. 

 under a pressure of ten atmospheres, and increasing to 400° 

 under a pressure of four atmospheres. He obtained about sixty 

 per cent, of an oil distillate of 0.815 specific gravity. Thirty- 

 seven per cent, of the distillate was taken out by shaking with 

 sulphuric acid, indicating unsaturated hydrocarbons, while the 

 remainder yielded, on fractional distillation, pentane, hexane, 

 normal and secondary hexane, normal octane and nonane. A 

 burning oil fraction was separated, and in his latest experiments 

 solid paraffine was also obtained from the heavier portions. Prof. 

 Engler gave a resume of his experimental results at the World's 

 Fair Congress of Chemists, in Chicago, in August, 1893, and I had 

 the pleasure of hearing it and examining his specimens at that time. 

 In consequence of this work of Engler, which he extended later to 

 lard oil as well as to menhaden oil, and to artificial tri-oleines as 

 well, the belief in the animal origin of petroleum has become quite 

 the prevalent one. 



Let us, however, take up for a moment the idea of the joint ani- 

 mal and vegetable source. This joint origin was advocated first of 

 all by Prof. J. P. Lesley, the Director of the Second Geological 

 Survey of Pennsylvania, and an honored Vice-President of this 

 Society. He believes that ''it is in some way connected with the 

 vastly abundant accumulations of Paleozoic sea weeds, the marks of 

 which are so infinitely numerous in the rocks, and with the infini- 

 tude of coralloid sea animals, the skeletons of which make up a 

 large part of the limestone formations which lie several thousand 

 feet beneath the Venango oil-sand group. ' ' The same view was held 

 by the late C. A. Ashburner, of the Pennsylvania Geological Survey. 



Prof. Edward Orton, of the Ohio Survey, summarizes his views 

 in the following postulates: (i) Petroleum is derived from organic 

 matter; (2) Petroleum of the Pennsylvania type is derived from 

 the organic matter of the bituminous shales and is probably of vege- 

 table origin ; (3) Petroleum of the Canada type is derived from 

 limestones and is probably of animal origin. 



Prof. Peckham, in his report on Petroleum for the Census of 

 1880, also makes a distinction in the origin of different classes of 

 petroleums. He divides all bitumens into four classes : 



I. Those bitumens that form asphaltum and do not contain par- 

 affine. 



