34 



NATURE 



\_May Qf, 1878 



energy in disturbances evidently of equatorial origin 

 when they reach the Pacific coast of the United States 

 and the coast of Spain. Unless the direction of the zone 

 of high pressure along the south margin on which they 

 move forms an angle of more than forty-five degrees with 

 the equator, the storm has a tendency to pass through it, 

 and in doing so expends much of its energy. 



Jerome J. Collins 

 {To be continued.) 



GAS AS FUEL 



ATTEMPTS have been made from time to time to 

 use gas as a means for heating ; these attempts 

 hare more frequently failed than succeeded, chiefly by 

 reason of the mechanical difficulties to be overcome. 



It is pretty generally agreed that, on account of the 

 ease with which the supply of a gaseous fuel can be regu- 

 lated, the completeness with which such a fuel can be 

 burned, the comparative readiness with which cleanliness 

 can be maintained while using this fuel, and by reason 

 of its high heating power, and for other reasons, gaseous 

 fuel is to be much preferred to fuel in the solid form. 



The most perfect gas for heating purposes would be 

 that, the constituents of which should be all combustible, 

 should be possessed of high thermal powers, and should 

 produce, on burning, compounds of small specific heat. 

 No gas which has yet been produced for use as fuel com- 

 pletely fulfils these conditions. 



Common coal-gas contains such non-combustible bodies 

 as carbondioxide and nitrogen, and among the pro- 

 ducts of its combustion is water, a body of large specific 

 heat, and also requiring a considerable amount of heat 

 to convert it into vapour. The complete combustion of 

 coal gas also necessitates a comparatively large supply of 

 air, and this, again, involves special mechanical appliances. 

 Nevertheless, coal-gas has been proved to be, for cer- 

 tain purposes, a cheaper, more effective, and more easily 

 managed fuel than coal, wood, or other forms of solid 

 heat-giving material. 



That steam is decomposed by hot carbon with the 

 production of a gaseous mixture of considerable heating 

 powers, has long been known, and several attempts have 

 been made to utilise the products of this decomposition. 

 These attempts have met with no great success on 

 account of the cost of the plant required to work the 

 manufacture and of the difficulties of the process. 

 Long-continued experiments have, however, been 

 carried on, and it would appear from a paper recently 

 communicated to the Society of Arts by Mr. S. W. 

 Davies, that these experiments have been crowned with 

 a very fair measure of success. 



The great difficulty was a mechanical one : it has 

 been very simply overcome. Superheated steam is pro- 

 duced in a coil placed within a cylinder and is driven by 

 its own tension in the form of a jet into the lower part 

 of an anthracite fire. The jet of steam carries with it 

 air sufficient to actively maintain the combustion of the 

 anthracite ; the gases issue at the top of the apparatus and 

 pass into the mains. The fire is fed from the top by an 

 arrangement which allows of the process being con- 

 tinuous. Water is forced into the coil under a pressure 

 varying from 15 lbs. to 40 lbs. on the square inch. The 

 whole apparatus is compact and simple. 



The products of the decomposition of steam by hot 

 carbon are mainly hydrogen and carbon monoxide; 

 traces of marsh gas are also formed. Could these gases 

 be produced free from admixed non-combustible bodies 

 we should have a gas of very high heating powers. But 

 the temperature of the glowing carbon must be main- 

 tained by the introduction of oxygen, that is, in practice, 

 by the introduction of air. The problem how to intro- 

 duce air sufficient to keep up vigorous combustion, and at 

 the same time to maintain the decomposition of the 

 steam, appears to have been satisfactorily solved ; but 

 the introduction of air means a lowering of the heating 

 power of the gas produced, inasmuch as four volumes of 

 nitrogen are brought in along with every volume of 

 oxygen supplied. By passing the gas through a series o 

 vessels containing hot carbon the nitrogen may be very 

 much diminished in amount, and the heating power of 

 the gas proportionally increased. 



The gas produced by the decomposition of steam by 

 hot carbon always contains traces of carbon dioxide 

 which is non-combustible ; the amount of this compound 

 may, however, be reduced to 3 or 4 per cent, by regulating 

 the depth of the layer of hot carbon through which the 

 gases pass, and by maintaining the temperature of that 

 carbon at a high point. But the maintenance of a high 

 temperature throughout a mass of carbon can be accom- 

 plished, under the conditions of the manufacture, only 

 by introducing a rapid current of air, which again means 

 a dilution of the gas produced. 



If, therefore, means could be found forefeeding the 

 anthracite fire with oxygen, a gas of very high heating 

 power might be produced. A supply of oxygen at a 

 cheap rate is a great desideratum; the gas exists in 

 practically unlimited quantity in the atmosphere, but an 

 easy and successful method for separating it from the 

 nitrogen with which it is there mixed is still only hoped 

 for by the chemical manufacturer. Were a supply of 

 oxygen forthcoming, mechanical difficulties would present 

 themselves before it could be utilised in the production 

 of "water gas." The introduction of too small an 

 amount of oxygen would mean the non-decomposition of 

 the whole of the steam and the cessation of the combus- 

 tion of the anthracite; the introduction of too much 

 oxygen would mean the production of carbon dioxide in 

 considerable quantity. But by regulating the size of the 

 steam jet and of the blast-pipe, these difficulties might 

 probably be overcome. 



As the gas is now produced all danger of explosion is 

 removed. 



The heating effect of the gas as at present manufactured 

 is about one-fifth that of ordinary coal-gas, for equal 

 volumes ; but the cost of the gas is so much less than 

 that of coal-gas, that a given amount of heating work 

 may be done — according to the figures given in the paper 

 referred to — by using the new gas, with a saving of from 

 one-third to 'two-thirds of the expenditure which would 

 be involved were coal-gas employed. 



Although the new gas is not perfectly adapted for the 

 purposes for which it is to be used, yet there can be 

 little doubt that we are now a step, and a very consider- 

 able step, nearer the final solution of the problem. 

 Doubtless improved furnaces, and improved apparatus 

 generally for burning the improved fuel, will be introduced. 



