530 



NA TURE 



[September 29, 1892 



duction of ammonia from peat alonq; with gas according to his 

 method will probably pay for gasifying the fuel and materially 

 facilitate the utilization of peat. 



Much to my surprise and regret this work remains the sole 

 practical outcome of our efforts in the direction of peat utiliza- 

 tion during the fuel famine of 1872, so far as Ireland is concerned. 

 Manufacturers now know how they can economically use peat 

 for high temperature operations, and Dr. Bindon Stoney, F. K. S. , 

 has suggested that peat should be gasified at the bogs and 

 carried to convenient centres of industrial activity. This could 

 undoubtedly be done, especially if instead of ' producer ' gas a 

 fuel were manufactured approaching water-gas in composition, 

 and such a gas of good calorific power can be manufactured 

 from peat. Thus, as in the case of coal, peat could be male 

 economically to provide light and heat energy as well for 

 domestic use as for manufacturing purposes. Would that we 

 could apply even a small portion of the energy stored up in peat 

 to stimulate those who should be most active in utilizing in the 

 best and most economical way the abundant material almost at 

 their doors ! 



If, then, there are many and great advantages in converting 

 our bulky solid fuels into gas and distributing them in that form 

 for heating purposes or supplying power by means of gas engines, 

 it is clear that such advantages must be confined for the most 

 part to towns or special manufacturing centres unless the gases 

 are condensed to the liquid form, and so rendered portable to 

 considerable distances ; but nature has already done a great part 

 of this work for us in providing the wonderful material we call 

 petroleum. I do not think ' wonderful ' is too strong an adjec- 

 tive to apply to this material, whether we consider its nature, 

 speculate as to its probable origin, or attempt to measure its 

 value in the world's work ; and in this, the concluding section of 

 my address, I propose to sketch in broad outline the main points 

 of public interest which relate to this, the most important of our 

 liquid fuels. . . . 



The views of geologists as to the nature of the general process 

 by which petroleum is formed are elaborately discussed in the 

 eighth report of the United States Geological Survey, and the 

 conclusions are there carefully summarized (page 506). In sub- 

 stance they are as follow : —That petroleum is derived from 

 organic matter by a process of slow distillation at comparatively 

 low temperatu»es : that the organic matter was not in all cases 

 of vegetable origin, but was in some instances derived from 

 animal substances in contact with limestone ; and, finally, that 

 the stock of petroleum in the rocks is practically complete. It 

 follows, of course, that the supply is exhaustible, but geologists 

 do not even guess at its duration. 



In contrast with all this is Mendeleeffs view that petroleum 

 is not a product from organic material, but is chiefly formed By 

 the action of water at high temperatures on carbide of iron, 

 which he supposes to exist in abundance within or below the 

 earth's crust. The cracks and fissures caused by the upheaval 

 of mountain chains permit water to reach the heated carbide at 

 great depths, and carbides of hydrogen result in accordance 

 with the general equation — 



3 Fe,„C„ -f 4 WH2O = wFegO^ + C^n^^,n. 



The hydrocarbides then distil up and condense within the cooler 

 sedimentary strata. The occurrence of petroleum in active 

 volcanic areas, as in Sicily and Japan, is held to accord with 

 this hypothesis, which latter is also consistent with the remark- 

 able fact that rock oil is usually found in the vicinity of moun- 

 tains. But my chief reason for referring to this attractive 

 hypothesis is that it permits us to suppose the hydrocarbides are 

 still being formed within the earth's shell, especially beneath 

 the geologically modern mountain chains, and that the supply 

 of petroleum is practically inexhaustible. Whether that view 

 can be sustained we must leave further evidence to decide, and 

 now return after this digression to the consideration of the 

 material itself. 



The porous strata saturated with petroleum often lie at con- 

 siderable depths below the surface soil of the district, and 

 the oil is in many cases prevented from rising by a bed 

 or shell of almost impervious material. In boring for the 

 oil this enclosing shell is penetrated and the result often is 

 the ejection of a column of liquid rising as a fountain of 

 several hundred feet into the air. This violent expulsion of 

 petroleum is due in great part to the pressure of pent up gases, 

 and the crude liquid always contains some of these gases in I 

 solution. In some instances gas only issues, and a so-called j 

 NO. I 196, VOL. 46] 



'gas well' is obtained, from which are emitted enormous 

 volumes of marsh-gas and its lower homologues, as well as 

 hydrogen. Some of these American, gas wells afford from lo to 

 14 million cubic feet per day, delivered at a pressure of as 

 much as 400 pounds to the inch. Such gas is a fuel of high 

 value and, as you know, has been largely utilized for industrial 

 and domestic purposes at such great industrial centres as 

 Pittsburg. 



One million cubic feet of the natural gas obtained from the 

 Trenton limestone at Findlay, Ohio, are said to do the same 

 amount of work in heating as about 60 tons of Pittsburg coal. 

 Some of these gas wells have been exhausted, but others have 

 continued in full productiveness for several years. Although 

 this natural gas is compressed and transported in cylinders to 

 considerable distances, it evidently must remain of almost 

 exclusively local value ; not so the liquid petroleum which 

 issues along with it or in its immediate neighbourhood. This is 

 the most portable of all fuels obtainable in nature, and therefore 

 is the most convenient means by which light and heat can be 

 transmitted to all parts of the world — hence it is of greater 

 practical interest to us than the natural gas. 



You are aware that the hydrocarbides of which the American 

 petroleum consists chiefly belong to the saturated group 

 CnHgn + 2. whereas those of Russian petroleum are mainly 

 benzenoid hydrocarbides of the general formula Q„\i^,„ isomeric 

 with the olefines, but really hydrogenized aromatic compounds 

 cf the naphthene series. Petroleum from both sources affords 

 some of the lower homologues of marsh-gas, hence in the pro- 

 cess of refining crude petroleum by distillation the first products 

 consist largely of butane, pentane, and hexane, which are 

 separated and condensed by pressure, the product being used for 

 refrigerating purposes, owing to its high volatility. Between 80° 

 and 1 20° American petroleum affords a spirit of specific gravity 

 about o°'75, and above 130° the illuminating oils are obtained, 

 whose gravities vary about 0"8, while the residue which 

 is not vaporized at 300° includes the heavier lubricating oils, 

 which are also admirably suited for use as fuel, and are cheaper 

 than those generally used for lighting purposes. During this 

 process of refining by simple distillation there is always more or 

 less decomposition ia progress, hydrocarbides of high molecular 

 weight being resolved into simpler ones at a comparatively high 

 temperature ; and when crude petroleum or its constituents are 

 rapidly heated, this resolution can be carried so far as to convert 

 a large proportion of the oil into permanent gas, valuable alike 

 for illuminating and heating purposes. Thus petroleum is a 

 fuel which can be permanently gasified with facility, and is no 

 doubt wholly converted into gas just prior to combustion in our 

 common lamps. 



Several methods are employed for the conversion of oil into 

 rich gas, and storing the latter for distribution through tubes in 

 the ordinary way. In one class of such processes the oil alone 

 is rapidly heated to a temperature of from 800° to 1000° in iron 

 retorts, as in the methods of Pintsch and Keith, thoroughly de- 

 scribed by Dr. Armstrong in vol. iii. of our Journal. The yield 

 of gas seldom exceeds 130 cubic feet per gallon, as liquid hydro- 

 carbides of low boiling points are condensed chiefly during the 

 compression of the gas into cylinders for use in railway carriages. 

 The gas is rich in carbon compounds, including methane, 

 ethylene, and crotonylene, and its illuminating power, even 

 after compression, is seldom less than forty-five candles. I may 

 add that Mr. Ivison Macadam has given in vol. vi. of our 

 Journal (p. 199) a valuable series of observations on the gas- 

 producing power of various oils treated by a process very 

 similar in plan to that of Pintsch. 



Another mode of converting petroleum into gas includes the 

 use of steam, as in the process of Messrs. Rogers, of Watford, 

 who inject the oil into red-hot retorts by means of steam, the 

 latter appearing to facilitate the permanent change of the 

 petroleum without the formation of much carbon monoxide. 

 The gas so produced is said to amount to about 140 feet per 

 gallon of heavy oil used, and has, according to Mr. Rowan 

 (this Journal, vol. vii), the following composition : — 



Per cent. 



Hydrogen 3i'6i 



Marsh-gas 46"I7 



Illuminants i6'29 



Carbonic oxide o'i4 



Nitrogen 5 "06 



Oxygen 073 



