Sept. 19, 1889] 



NATURE 



513 



run into the tender or into the oil-bunkers of a ship. As a 

 working agent in heat-engines it is employed in two ways. 

 First as vapour, generated from the lic^u'd petroleum contained 

 in a boiler, very much in the same way as the vapour of water is 

 used in an engine with surface condenser, the fuel for producing 

 the vapour being also petroleum. Very signal success has been 

 obtained by Mr. Yarrow and others in this mode of using mineral 

 oil, especially for marine purposes and for engines of sma'l 

 power ; there seems to be no doubt that by using a highly vola- 

 tile spirit in the boiler a given amount of fuel will produce 

 double the power obtainable by other means, and at the same 

 time the machinery will be lighter and will occupy less space than 

 if steam were the agent used. The other method is to inject a 

 very fine spray of hot oil, associated with ilie proper quantity of 

 air, into the cylinder of an ordinary gas-engine, and ignite it 

 there by means of an electric spark or other suitable means. 

 Attempts to use oil in this way date back many years, but it was 

 not till 1888 that Messrs. Priestman Brothers exhibited at the 

 Nottingham Show of the Royal Agricultural Socit ty an engine 

 which worked successfully with oil, the flashing-point of which 

 was higher than 75° F., and was therefore within the category 

 of safe oils. The engine exhibited was very like an ordinary 

 Otto gas-engine, and worked in exactly the same cycle. A pump 

 at the side of the engine forced air into a su all receiver at a few 

 pounds' pressure to the square inch. The compressed air, 

 acting by means of a small injector, carried with it the oil in 

 the form of fine spray, which issued into a jacketed chamber 

 heated by the exhaust, in which the oil was vaporized. The 

 mingled air and oil was thus raised to a temperature of about 

 300°, and was then drawn, with more air, into the cylinder, 

 where, after being compressed by the return stroke of the piston, 

 it was exploded by an electric spark, and at the end of the 

 cycle the products of combustion were discharged into the air 

 after encircling the spray chamber and parting with most of 

 their heat to the injected oil. The results of careful experi- 

 ments made by Sir William Thomson and by myself on different 

 occasions were, that 1 73 pound of petroleum was consumed per 

 brake-horse power per hour ; but the combunion was by no 

 means perfect, for a sheet of paper held over the exhaust-pipe 

 was soon thickly spattered with spots of oil. 



At the Windsor Show of the Royal Agricultural Society 

 this year, Messrs. Priestman again exhibited improved forms of 

 their engine ; the consumption of oil fell to i '25 pound per 

 brake-horse power per hour, and a sheet of paper held over the 

 2xhaust remained perfectly clean. They also showed a portable 

 engine of very compact construction, and quite adapted to agri- 

 cultural use ; the ordinary water cart, which has, in any case, to 

 attend a portable steam-engine, being adapted to supply the 

 water necessary to keep the working cylinder of the engine cool. 

 I, It is hardly necessary to state that the use of petroleum for 

 nrnace purposes of all kinds is increasing very rapidly, and the 

 iemand has naturally reacted on the supply in promoting im- 

 proved means of transport ; and Newcastle, again, has led 

 he van in this matter, for Sir William Armstrong, Mitchell, and 

 "o., Messrs. Palmer, and others have sent out a fleet of steamers 

 :onstructed to carry ihe oil in bulk with perfect safety, both as 

 egards the stowage of a cargo so eminently shifting, and with 

 espect to risk from fire and from explosion. 



The enormous consumption of petroleum and of natural gases 

 rcquently raises the question as to the probability of the proxi- 

 nate exhaustion of the supply ; and, without doubt, many fear 

 o adopt the use of oil, from a feeling that if such use once 

 )e_comes general the demand will exceed the production, the 

 )rice will rise indefinitely, and old methods of illumination, and 

 Id forms of fuel, will have to be reverted to From this point 

 f view it is most interesting to inquire what are the probabilities 

 if a continuous supply ; and such an investigation leads at once 

 o the question, " What is the origin of petroleum?" In the 

 ear 1877, Prof. Mendeleeff undertook to answer this question ; 

 nd as his theory appears to be very little known, and has 

 ever been fully set forth in the English language, I trust you 

 all forgive me for laying a matter so interesting before you. 

 )r. Mendeleeff commences his essay by the statement that most 

 ersons assume, without any special reason — excepting, perhaps, 

 ;s cheniical composition — that naphtha, like coal, has a vege- 

 ible origin. He combats this hypothesis, and points out, in 

 le first place, that naphtha must have been formed in the 

 epths of the earth. It could not have been produced on the 

 irface, because it would have evaporated ; nor over a sea 

 ottom, because it would have floated up and been dissipated 



by the same means. In the next place, he shows that naphtha 

 must have been formed beneath the very site on which it is 

 found ; that it cannot have come from a distance, like so many 

 other geological deposits, and for the reasons given above — 

 namely, that it could not be water-borne, and could not 

 have flowed along the surface, while in the superficial sands in 

 which it is generally found no one has ever discovered the 

 ])resence of organized matter in suiTiciently large masses to have 

 served as a source for the enormous quantity of oil and gas yielded 

 in some districts ; and hence it is most probable that raphtha 

 has risen from much greater depths under the influence of its 

 own gaseous pressure, or floated up upon the surface of water, 

 with which it is so frequently associated. 



The oil-bearing strata in Europe belong chiefly to the Tertiary 

 or later geological epochs ; so that it is conceivable that in these 

 strata, or in those immediately below them, carboniferous 

 deposits may exist and may be the sources of the oil ; but in 

 America and in Canada the oil-bearing sands are found in the 

 Devonian and Silurian formations, which are either destitute of 

 organic remains, or contain them in insignificant quantities. 

 Yet if the immense masses of hydrocarbons have been produced 

 by chemical changes in carboniferous beds, equally large masses 

 of solid carboniferous remains must still exist ; but of this there 

 is absolutely no evidence, while cases occur in Pennsylvania 

 where oil is obtained from the Devonian rocks underlying com- 

 pact clay beds, on which rest coal-bearing strata. Had the oil 

 been derived from the coal, it certainly would not have made its 

 way downwards ; much less would it have penetrated an im- 

 permeable stratum of clay. The conclusion arrived at is, that it 

 is impossible to ascribe the formation of naphtha to chemical 

 changes produced by heat and pressure in ancient organized 

 remains. 



One of the first indices to the solution of the question lies in 

 the situation of the oil-bearing regions. They always occur in 

 the neighbourhood of, and run parallel to, mountain ranges, — 

 as, for example, in Pennsylvania, along the Alleghanies ; in 

 Russia, along the Caucasus. The crests of the ranges, formed 

 originally of horizontal strata which had been forced up by 

 internal pressure, must have been cracked and dislocated, the 

 fissures widening outwards, while similar cracks must have been 

 formed at the bases of the ranges ; but the fissures would widen 

 downwards, and would form channels and cavities into which 

 naphtha, formed in the depths to which the fissures descended, 

 would rise and manifest itself, especially in localities where 

 the surface had been sufficiently lowered by denudation or 

 otherwise. 



It is in the lowest depths of these fissures that we must seek 

 the laboratories in which the oil is formed ; and once produced, 

 it must inevitably rise to the surface, whether forced up by its 

 own pent-up gases or vapours, or floated up by associated water. 

 In some instances the oil penetrating or soaking through the 

 surface layers loses its more volatile constituents by evaporation, 

 and, in consequence, deposits of pitch, of carboniferous shales, 

 and asphalte take place ; in other cases, the oil, impregnating 

 sands at a lower level, is often found under great pressure, and 

 associated with forms of itself in a permanently gaseous state. 

 This oil may be distributed widely according to the nature of 

 the formations or the disturbances to which they have been sub- 

 jected ; but the presence of petroleum is not in any way connected 

 with the geological age of the oil-bearing strata : it is simply the 

 result of physical condition and of surface structure. 



According to the views of Laplace, the planetary system has 

 been formed from incandescent matter torn from the solar 

 equatorial regions. In the first instance this matter formed a 

 ring analogous to those which we now see surrounding Saturn, 

 and consisted of all kinds of substances at a high temperature, 

 and from this mass a sphere of vapours, of larger diameter than 

 the earth now has, was gradually separated. The various, 

 vapours and gases which, diffused through each other, formed 

 at first an atmosphere round an imaginary centre, gradually 

 assumed the form of a liquid globe, and exerted pressures incom- 

 parably higher than those which we experience now at the base 

 of our present atmosphere. According to Dalton's laws, gases,, 

 when diffused through each other, behave as if they were 

 s eparate ; hence the lighter gases would preponderate in the 

 outer regions of the vaporous globe, while the heavier ones 

 would accumulate to a larger extent at the central portion, and 

 at the same time the gases circulating from the centre to the 

 circumference would expand, perform work, would cool in 

 consequence, and at some period would assume the liquid or 



