36 Power and its Transmission. 



amounts to £2$ in London and ^"22 in Birmingham, being 

 proportionately reduced in larger engines. The cost of gas power 

 may be taken as £26 in London, and ^"20 is. iod. in Birming- 

 ham, ^"19 10s. in Glasgow, and ^"24 in Belfast per year power 

 unit. 



Referring at length to the production and development of 

 steam-power, Mr. Wilson said that during the last twenty- 

 five years, except in some minor points of construction, the 

 form and performance of boilers has been unaltered, tubular 

 boilers having then taken the place of flue, and steel has since 

 superseded iron as the material employed in their manu- 

 facture, and enabled much higher pressure to be carried with 

 safety. Much, moreover, has been accomplished in marine 

 engineering in the development of power, especially by the use 

 of compound engines. It may be mentioned that, while the 

 quantity of fuel to produce a pound of steam at 1 60 pounds 

 pressure is only 3 per cent, more than that necessary for the 

 production of a pound of steam at 30 pounds pressure, the avail- 

 able power obtainable from steam at 160 pounds is nearly 100 per 

 cent, more than from that at 30 pounds. It is for this reason 

 ..that high-pressure engines have become so generally used, and 

 though the advantages of such pressures were known long 

 ago, they could not be utilised, owing largely to the want of a 

 proper oil. Steam at 30 pounds pressure has a temperature of 

 274 Fahrenheit, and at 160 pounds pressure of about 370 . Of 

 the animal and vegetable oils applicable for lubricating purposes, 

 some of them at the lower temperature answer sufficiently what 

 is required, while at the higher they become completely car- 

 bonised and turn into gas. It was not, therefore, until some of 

 the products of petroleum were brought into use that this 

 difficulty was overcome. The only rival, and that an insignifi- 

 cant one, able to hold its own at all hitherto with steam as a 

 power for manufacturing and propelling agency is gas. In 

 gas engines the motive power is developed by an explosion of 

 a mixture of gas and air below the piston of a vessel resembling 

 a steam cylinder. Some manufacturers claim to be able to 

 work with 22 cubic feet of gas per horse-power, but this he had 



