506 FUEL 



'Tho plan of using liquid fuel, which so far as I am aware has proved the most ad* 

 vantageous, is one which does, to some extent at any rate, secure tho advantage to be 

 gained by forcing air into the furnace. According to this plan the oil is supplied to 

 the furnace through a small pipe, together with a jet of high-pressure steam, by which 

 it is converted into spray, much in tho same manner as, in tho toy known as the per- 

 fume-vaporiser, a liquid is blown out of a bottle by a current of air. Tho steam-jet 

 at tho same time induces a current of air which mixes with tho oil spray and supports 

 its combustion. This is the arrangement used by Messrs. Field and Aydon, and it 

 appears to work exceedingly well, effecting a very perfect combustion of the oil. Tho 

 oil I have seen used in this way was the dead oil, or creosote oil, which is a refuse 

 product in the refining of gas-tar. It possesses characters which render it much pre- 

 ferable to petroleum, or to the oil obtained by distilling coal at a low heat, for use as 

 liquid fuel. In the first place, its density being greater than that of water the gallon 

 weighing about 12 Ibs. it takes less space for stowage than petroleum or coal-oil, the 

 gallon of which weighs only from 8 to 8 Ibs. For the same reason it would not bo 

 so dangerous as the lighter oils in case of accident ; for instead of floating on the sur- 

 face of water and burning, it would sink harmlessly. Again, its very high boiling 

 point, approaching to a red heat, and the great density of its vapour as compared with 

 that of petroleum or coal-oil, are great advantages as regards risk of explosion in 

 consequence of the oil-vapour becoming mixed with air and then catching fire. This 

 could hardly take place with the dead oil, except at a very high temperature, while 

 petroleum readily gives off vapour to the air at a moderate degree of heat. 



'The use of this oil as fuel presents great advantages for gas-tar distillers, with whom 

 it is a troublesome waste product. If it should come into demand as steam-fuel its 

 value would of course rise above that of coal, to an extent proportionate to its greater 

 efficacy and any other advantages resulting from its application as steam fuel. Such 

 an application might therefore be a great advantage to gas companies. 



'Unfortunately the quantity of this oil which is available is very small as compared 

 with the requirements of steam navigation, probably not amounting to 100,000 tons a 

 year in the whole country, and therefore its application must be very limited. 



' In order now to arrive at some estimate of the advantage to be gained in a steam 

 vessel, either in point of weight to be carried, or space occupied by liquid fuel as com- 

 pared with coal, it is evident that 100 tons of petroleum, or coal-oil, would do tho 

 work of about 140 tons of good coal. But as coal is rarely burnt in such a way as to 

 be rendered useful to its full capability, and as there is always a considerable waste in 

 the shape of dust and cinders, which would not be the case with liquid fuel, a further 

 allowance must be made for this. Assuming that one-fifth of the coal is wasted in 

 this way, then the equivalent of 100 tons of oil would be 175 tons of coal, for taking 

 the density of the oil as '850, it would occupy about the same space as an equal weight 

 of coals, or at the rate of about 53 Ibs. per cubic foot. This difference would enable 

 a vessel capable of carrying coal for 12 days' steaming, to carry oil for 21 days. In 

 burning this oil there would be a saving of labour in stoking, and as it would not give 

 any ashes, a great deal of trouble would be saved in that way. 



'These results differ widely from the statements which have been made in reference 

 to the relative efficiency cf oil and coal, according to which it has been represented 

 that one ton of oil was equal to from 4 to 5 tons of coal, and that in regard to stowage- 

 room the saving was more than nine-tenths in bulk. I am not aware of any evidence 

 having yet been brought forward, such as would call for, or justify, the abandonment 

 of those well-established principles by which tho heating power and efficacy of fuel is 

 determined, as above stated. 



'Mr. Trickett, the engineer-in-chief of tho dockyard, gives, as the highest evapo- 

 rative effect obtained with petroleum, 11'63 Ibs. of water converted into steam per 

 pound of oil burnt. In this case, however, the combustion was imperfect. But in tho 

 most successful trials with coal-oil and shale-oil, when very little smoke was Driven oft', 

 the evaporative effect was about 18 Ibs. of steam produced per pound of oil burnt. 

 In this case some deduction is required to be made for the steam applied as a blast to 

 the fire, but the amount was not ascertained. This result was also obtained under 

 peculiarly favourable circumstances as regards tho proportion of heating surface of 

 the boiler to tho rate of evaporation. 



' In regard to the supply of material capable of being used as liquid fuel, it is 

 necessary to make a few remarks. Fir tdi petroleum, I imagine it is now 



generally acknowledged that this material in its natural state is not well adapted for 

 tho purpose. In that state it contains a large amount of very volatile hydrocarbon, 

 which, even at the ordinary temperature, vaporises by contact with air, and the mix- 

 ture of this vapour with air is explosive. At the temperature of a steam vessel's stoke- 

 hole this vaporisation would take place more readily, and if there were any leakage 

 in the supply pipes or tanks, disastrous consequences might ensue. In order to re- 



