348 SECTIONAL TRANSACTIONS.— G. 



that appropriate apparatus, such as resistances, condensers, and inductances are 

 included in the circuit. 



Since in a circuit consisting of a tube containing liquid resistance may be repre- 

 sented to some extent by fluid friction, inductance by mass, and capacity by storage, 

 it follows that, if such a tube can be provided with apparatus which will allow of 

 the free escape of liquid when a certain pressure is reached, and with a continuation 

 of that escape at a lower pressure afterwards, the condition of the electrical discharge 

 circuit may be imitated. 



Such an arrangement entails the use of a valve, which will open at a predetermined 

 pressure and remain open until a lower pressure has been reached. This is not easy 

 to provide by mechanical means. It may, however, be arranged by making use of 

 the phenomena of surface tension. If a siphon tube is made of gradually increasing 

 diameter, the potential energy of the meniscus increases as the diameter increases, 

 and consequently there will be a tendency 7 for the meniscus to contract against the 

 gravitational force of the liquid in the tube. If, therefore, the amount of liquid in 

 the tube increases, the meniscus expands until a certain limit is reached, when it 

 allows liquid to escape. This arrangement forms a very perfect automatic valve for 

 the purpose of a model to imitate the electric discharge. Such a model has been 

 made and will be shown. It is possible to imitate the production of electric oscillations 

 by the Duddell arc, the behaviour of the neon lamp when fed from a constant pressure 

 circuit with a resistance in series and condenser in shunt, and the behaviour of certain 

 phases of the Poulsen arc, as confirmed by photographs taken of cathode ray 

 oscillograms. 



Friday, September 2. 



Papers on Coal : — 



(«) Dr. C. H. Lander. — Our available Coal Supplies and their 

 Utilisation. 



(b) Prof. J. W. Cobb. — The Utilisation of our Coal Supplies. 



The author considers what are the factors at present limiting the applications of 

 carbonisation or similar processes to the great bulk of our coal supplies, and what 

 is being done or may be done to remove those limitations. Such processes entail a 

 thermal and monetary expenditure. If they are to be justified it must be by the 

 enhancement in value of the products sufficient to cover the cost. 



The high thermal efficiency of carbonisation is pointed out, and the enhanced 

 value of the heat unit in gas as compared with that in coal. The expenditure for 

 installing and working plants for carbonisation is high compared with the appliances 

 for the direct burning of coal, because the rate of combustion of coal in air is so very 

 much more rapid than the reactions involved either in carbonisation or gasification. 

 Hence the amount of work which is being done to speed up the working of processes 

 in one way and another. 



In carbonisation, apart from new designs of plant, studies are being made of the 

 influence of temperature of working, size of coal, the effect of blending and carbonisa- 

 tion of very fine particles. These are discussed, and also the results obtained, when 

 the behaviour of coal is modified by the introduction of small quantities of inorganic 

 constituents, such as iron oxide, lime and soda. Greatly enhanced rates of gasification 

 are so obtained with steam or carbon dioxide on the laboratory scale — reactions which 

 underlie the processes of making water gas and producer gas on the industrial scale. 



(c) Prof. R. V. Wheeler.— The Chemistry of Coal. 



The materials, all forms of plant structures, that may have contributed to the 

 composition of coal, are numerous and diverse in character. Except for certain specific 

 substances, too small in amount to require consideration here, these materials are, 

 however, substantially the same in chemical nature, though varying widely in form 

 and in the relative quantities present, whatever the type of plant life to which they 

 belong. The relative amounts of the different plant materials that ultimately form 

 coal may be considerably altered by the conditions of their accumulation in the 

 coal-forming beds. There trill, for example, be a tendency for the heavier woody 

 matter, containing much lignin and cellulose, to be segregated from the lighter 



