FUELS 395 



be mentioned. These include the study of the gases dissolved or occluded in metals and 

 removed by heating or even melting in vacuo, of the behaviour of metals in high vacua, 

 especially in the light of the theory of an amorphous inter-crystalline cement in metals, 

 of the magnetic properties of alloys, both of iron and of copper-aluminium-manganese, 

 and of the electrical resistance of alloys and its variations with temperature. 



For these and allied researches reference should be made to the original publications, 

 many of which exist only in foreign languages. In English, many original papers, and 

 abstracts of many others, including most of the more important foreign ones, will be found 

 in the Journal of the Iron and Steel Institute, the Journal of the Institute of Metals, the Pro- 

 ceedings of the Faraday Society and of the Institution of Mechanical Engineers, and in the 

 pages of Science Abstracts, devoted to physical chemistry. In French the Revue de Metal- 

 lurgie, and in German Stahl u. Risen, Metallurgie, and the Internationale Zeitschrift fur Melal- 

 lographie, may be consulted, as well as the more recent text-books upon this subject. 



(VV. ROSENHAIN.) 



SOLID, LIQUID AND GASEOUS FUELS 1 



i. Solid Fuel. 



Coal. In the middle of the ipth century a large amount of scientific work was done 

 concerning the composition of coal, and the view was held by many observers that the 

 N w views var i a tions in the properties of coals were dependent as much upon the 

 oa the com- character of the vegetable matter from which they had been formed as 

 position of upon the conditions of formation. These views however were more or less 

 lost sight of until the last couple of years, when they have again been brought 

 to the front, and are now shown to give a far more satisfactory explanation of many 

 obscure points with regard to the thermal vahie and chemical decomposition of coal than 

 was possible before. In 1911 M. J. Burgess and R. V. Wheeler published the results of 

 a series of experiments on the distillation of coal at various temperatures, which led 

 them to conclude that coal contained two types of compounds of different degrees of 

 ease of decomposition, the one a degraded product of cellulose, the other derived from 

 the gums and resins of the coal plants, and that the character of the coal is determined 

 by the proportion in which these two types exist in coal. 



V. Lewes puts forward the general theory of the formation and composition of coal 

 as follows. Carbon is practically non-existent in the primary rocks constituting the 

 crust of the globe; hence all the free carbon and compounds containing carbon that we 

 now find have been produced by secondary actions from carbon dioxide in the atmos- 

 phere, the amount present showing that the atmosphere in times prior to the carbon- 

 iferous period consisted of a high percentage of carbon dioxide, nitrogen, oxygen, and 

 water vapour. Human life under these conditions was impossible, but as the crust of 

 the cooling globe reached a sufficiently low temperature, a vegetable life of a low order 

 started and grew with a luxuriance and rapidity that could never again be equalled, 

 owing to the conditions of moist heat and plentiful carbon dioxide. As the vegetation 

 grew it absorbed the carbon dioxide and moisture, and under the influence of the sun's 

 rays built up the plant structure and evolved oxygen, thus in the course of geological 

 ages creating an atmosphere fitted for lower forms of animal life, which gradually be- 

 came of a higher order as the necessary oxygen increased in percentage. Owing to the 

 paucity and dilution of oxygen in the earlier periods, decay, as we now know it, could 

 take place only to a very limited extent, and this, with the rapidly growing flora of the 

 carboniferous period, gave rise to the enormous vegetable deposits and drifts from which 

 eventually all fuel was formed. 



All the plants of which there are fossilised records in our Coal Measures consisted of 

 sedges and reeds, tree ferns, club mosses or lycopodia, and trees akin to the pine; but in 

 these prehistoric days the conditions of growth were such that the plants grew with a 

 succulent freedom and rapidity since unknown, and this later rendered their tissues an 

 easy prey to fermentation an action which left only the more resistant unchanged. 

 The work of Morris, Carruthers, Fleming and Huxley has shown that the bituminous 



1 See. E. B. xi, 274 et seq. 



