July 1, 1898.] 



KNOWLEDGE. 



153 



place until the bulk of the lighter oila and "natural" 

 kerosene have been distilled oS, as it is the hea\aer and 

 less valuable constituents of the crude petroleum which it 

 is desired to decompose in order that the maximum of 

 kerosene may be obtained. The distillate is agitated with 

 sulphuric acid followed by a treatment with caustic soda 

 lye, and it is finally washed by agitation with water, from 

 which it is drawn off after settlement. The exact action 

 of the chemical treatment is not known, but it appears to 

 consist mainly in the removal of the tarry matters, the 

 aromatic hydrocarbons, and the sulphur compounds, all of 

 which injure the quality as well as mar the appearance of 

 the oil. 



The nature of the products obtained at different distil- 

 leries varies according to the market for which they are 

 intended. The oil allowed to be burnt in lamps in England, 

 for instance, must not " flash" — that is, giveoff inflammable 

 vapour in a closnl vessel — at a temperature below seventy- 

 three degrees Fahren., while in some countries the standard 

 is higher and in others lower. The principal products 

 recognized in the trade are : — (1) The lightest, i.e., the 

 most volatile constituents, known as petroleum spirit or 

 naphtha, which is sometimes again divided up into rhigo- 

 lene or cymogene, gasoUne, benzoline, benzine, etc. (2) 

 Kerosene for burning in lamps. This, the most important 

 of the products of petroleum, constitutes about seventy per 

 cent, of the yield from the oil of the United States and 

 about half as much from that of Kussia — a feature which 

 has had much to do with the greater success of the 

 Americans. (3) Oil somewhat heavier than kerosene, 

 but still capable of burning in suitably constructed lamps. 

 (41 Lubricating oil, which, on account of its feebler 

 action on metals and its less tendency to clog machinery, 

 as compared with the animal and vegetable oils formerly 

 exclusively used, has now practically displaced the latter 

 in the markets of the world. (5) Paraffin wax. (6) 

 Vaseline. And (7) residuum, or waste, now used on an 

 enormous scale as liquid fuel. Anthracene and other 

 compounds from which dye-stuffs may be obtained have 

 also been separated from the residuum, but the cost has 

 so far proved prohibitive. 



The uses to which these various products have been put 

 are very numerous. The earliest use of petroleum was, as 

 already stated, for medicinal purposes — an application now 

 mainly confined to vaseline and the softer paraffin waxes, 

 which are largely used in preference to lard in the manu- 

 facture of pomatum, etc. It is stated that vaseline, as well 

 as much of the heavier petroleum oil, is used instead of 

 butter in the manufacture of pastry on a large scale, but 

 it is doubtful whether it possesses any value whatever as 

 a food. 



The lightest of the petroleum spirits are used as local 

 anassthetics, those of lesser volatUity being largely employed 

 as solvents for waterproofing materials, varnishes, and as 

 cleansing agents for the removal of grease spots ; also in 

 the processes of " dry cleaning " for fabrics. It is, of 

 course, as a lighting agent that petroleum is most used, 

 the distillates known as kerosene being employed for that 

 purpose, and the bulk of the candles now in use are 

 prepared from the paraffin wax obtained from petroleum. 



The use of the heavier oils as lubricants has already 

 been referred to, but it may be mentioned that the Russian 

 oil holds the field as the best for this purpose, although 

 its kerosene has not so good a name as that of America, 

 mainly on account of the fact that the lamps (especially 

 those in use in England) are especially designed for burning 

 the American oil, which does not require so good an air 

 supply for its combustion as does the Russian. 



For use as fuel, the Russian residuum is preferred to 



that of America on account of its greater fluidity. Under 

 the name " astatki," or " masut," it is largely employed 

 as fuel for stationary and locomotive engines, marine 

 boilers, furnaces, etc., a jet of the sprayed residuum blown 

 into the furnace by a blast of air or steam from a nozzle 

 being the usual method of applying it. On account of the 

 ease, with which this residuum may be stored, and, above 

 all, of the almost total absence of smoke and dirt during 

 its combustion and the little attention and stoking which 

 is required, it is probable that in the near future its use on 

 board ship will be greatly augmented. 



Finally, the use of petroleum distillates for enriching 

 coal gas, either by merely passing the gas through the 

 highly volatile gasoline, or by decomposing the heavier 

 oil into illuminating gas, which is mixed with the coal gas, 

 must be mentioned, together with the large and increasing 

 use for " petroleum engines," in which vaporized or gasified 

 petroleum spirit, or even kerosene, is exploded with air as 

 in the gas engines, which some practical men consider will 

 ultimately be replaced by those using petroleum. 



ON THE ECLIPSE THEORY OF VARIABLE 

 STARS. 



By Lieut. -Colonel E. E. Maek^ick, k.r.a.s. 



THE theory that the variations in light of such stars 

 as Algol are due to the presence of a dark or opaque 

 companion star, which periodically passes between 

 us and the bright star, is generally accepted as 

 satisfactorily accounting for the observed changes 

 in brightness. Vogel's almost classical determination of 

 the elements of the system of Algol, uniting as it does 

 the visual and spectroscopic observations, seems to have 

 clinched the theory, and it has crystallized into a recog- 

 nized fact in the text-book and lantern-slide worlds. It is 

 with no idea of controverting this theory that this paper is 

 written, but simply to examine some of the conditions 

 which are attached to it, and study them from different 

 points of view. 



For this purpose five different systems, each of two 

 bodies revolving round their centre of gravity, are pro- 

 pounded. The two bodies are denominated A and B 

 respectively, and the following table gives the particulars 

 of each : — 



With these data, the diminution in the light of A by the 

 central transit of B was calculated for every one-tenth 

 of diameter of A that B advances on its course, supposing 

 B to move from right to left. Thus in Fig. 1 the area of 

 the hme D E F G was calculated when the advancing limb 

 of B had arrived respectively at 1, 2, 3, etc. Fig. 1 shows 

 the occulting satellite (System I.) arrived at point 3. In 

 this particiJar case the area of the lune is 14 31, the 

 distance G E («) being :->. Taking the light of globe A to 

 be represented by unity, the Hght cut off" is -182 ; the 

 remaining light is SIS. Assume the " magnitude " of A 

 when quite unobscured as 1-0 ; then the resulting mag- 



