April 6, 1905] 



NA rURE 



S.^i 



makes no pretence of doing, as, of course, its dis- 

 tinguished authors would at once admit. But mass, 

 as we have seen, is not conventionally defined with 

 reference to gravity, but by means of inertia, or 

 momentum at unit velocity. As a moving electric 

 charge can be shown to possess this momentum, it is 

 a strictly correct use of words to say that the electron 

 theory explains the property of mass. 

 . Dr. Hampson argues, in the second place, that 

 electricity is a form of energy, and that it cannot there- 

 fore be identified with matter. 



" When an electrical machine ... is used to charge 

 ,1 Levden jar . . . there is no change in the quantity 

 iif material substance with which operations were 

 --tarted ; it is the mechanical energy driving the 

 niachinerv that has been converted into electricitv '" 

 (p. S7). 



The misconception here lies in confusing the separa- 

 tion of positive and negative electricity with the 

 creation of either. Take the case of a Leyden jar. 

 The coatings of the jar, according to modern views, 

 initially both contain a number of chemical atoms, all 

 with their normal complement of constituent electrons. 

 The operation of charging consists in the removal 

 of some of these electrons from the outer coating, 

 say, and their transference to the inner one. This 

 leaves the outer coat with a defect of electrons, and 

 therefore positively charged, while the inner one 

 acquires an excess of them, and consequently becomes 

 negatively charged. The transference involves the 

 expenditure of energy on the electrons, but no alter- 

 ation in their number, and therefore no change in 

 the amount of matter concerned. 



We are sorry to have had to dwell principally on 

 the parts of the book with which we disagree, as 

 these are but a small portion of the whole, and do 

 not detract from the usefulness of the rest. 



R. J. S. 



OIL FUEL. 

 Oil Fuel: Its Supply, Composition and Application. 



By S. H. North. Pp. viii+152. (London: Chas. 



Griffin and Co., Ltd., 1905.) Price 55. net. 

 jyrR. SYDNEY H. NORTH has utilised the store 

 of data collected whilst he was editor of the 

 Petroleum Review to supply a most valuable addition 

 to Griffin's scientific text-books in his work on " Oil 

 Fuel " and to give his readers a concise and valuable 

 record of the developments in the use of liquid fuel 

 for the generation of power. 



In the first chapter of the book he deals with the 

 distribution and sources of supply of petroleum, and 

 points out that the chief sources are now so geo- 

 graphically situated as to place the United Kingdom 

 at a disadvantage in case of war, should the use of 

 liquid fuel be largely adopted in the Naval Service, 

 a fact which accentuates the importance of develop- 

 ing such fields as those of Canada and Burmah, and 

 also of opening up new areas where possible in British 

 Possessions. 



In concluding this portion of the work, the author 

 expresses his opinion that recent developments and 

 extensions of oil-bearing areas are now progressing 

 NO. 1849, VOL. 71] 



so rapidiv that it is quite within the bounds of 

 possibilitv that the liquid-fuel question may in the 

 near future be placed above the control of price and 

 geographical position. 



In dealing with the economic aspect of liquid fuel 

 it is pointed out that although the enormous 

 advantages accruing from its use were early 

 recognised, the prohibitive price prevented any great 

 advance in its use, but that with the increase in out- 

 put its utilisation now comes within the range of 

 practical possibility, and that the advantages in 

 winning, transporting, and storing and using the 

 oil, especially for marine purposes, are so great that 

 the supply of the liquid fuel is now the only factor 

 checking its universal introduction. 



In considering the absolute economy as a fuel, the 

 author very properly leaves out the extravagant 

 claims made by some of the early experimentalists,, 

 and only gives the best authenticated values, which 

 vary from 12.5 to 16 lb. of water evaporated per lb. 

 of liquid fuel. Variations in the use of oil as a fuel 

 are of course largely dependent upon the method by 

 which the oil is burnt, and too little stress is put upon 

 the importance of the space factor, which is a most 

 essential one, as, given plenty of combustion space in 

 the boiler, the smokeless burning of liquid fuel is a 

 perfectly simple problem, which, however, increases 

 enormously in difficulty as the available space becomes 

 more and more cramped. 



The chapter on the chemical composition of fuel 

 oils gi\-es an excellent summary of analytical results, 

 and this ends with a table showing the composition, 

 calorific value and evaporative power of different 

 descriptions of British coal. This, however, is liable 

 to lead to misconception, as the value expressed in 

 lb. of water evaporated per lb. of fuel is calculated,, 

 and not that obtained in practice, so that the reader 

 who finds that by this table i lb. of Welsh coal will 

 evaporate 14-98 lb. of water will be a little puzzled 

 to see where the large economy comes in, when i lb. 

 of oil only evaporates from 12.5' to 16 lb. of water. 

 .As a matter of fact, all recent work points to the 

 relative evaporative results under the best conditions, 

 being 9 lb. of water per lb. of coal, or 15 lb. of water 

 per lb. of oil, whilst the theoretical results give 

 14.98 lb. of water for coal, and 20 to 21 lb. for oil. 



Tlie section dealing with the conditions of com- 

 bustion in oil furnaces is a useful reproduction of the 

 views expressed by Messrs. Ord, Paul, and Lewes, 

 and the author does not venture on any generalisation 

 of his own. 



Turning from consideration of the oil itself to the 

 methods of burning it, the author gives a ver)' useful 

 historical summary of the early experiments down to 

 the year 1883, when Mr. James Holden, whose name 

 will always be Inseparably connected with the subject 

 of liquid fuel, introduced his method of consuming the 

 oil on the Great Eastern Railway. 



A chapter is then devoted to modern burners 

 and methods, and steam, air, and mechanical 

 injectors are discussed. The author very properly 

 concludes that 



" for the successful use of liquid fuel it appears 

 to be a sine qua )wii that auxiliary apparatus. 



