Power and its Transmission. 35 



by gunpowder in cannon, which is measured by artillerists 

 in " foot tons." One of the 100-tons guns manufactured by 

 Sir William Armstrong's firm for the Italian Government 

 developed and communicated to a target placed 100 yards away 

 a power equal to 40,000 foot tons. This power, if able to be 

 maintained continuously, would be immense ; for the energy 

 developed by one discharge only of this gun would be sufficient 

 to lift, say, either of the Liverpool steamships Caloric and 

 Optic, weighing, with cargo, coal, crew, and passengers, some 

 1,410 tons, to a height of thirty-one feet in ten seconds. Unfor- 

 tunately, however, this great source of power is applicable to few 

 except warlike purposes. 



The supply and sale of power for manufacturing and indus- 

 trial purposes is of quite recent development, but has already 

 become a recognised system in many large towns where manu- 

 factures or works are carried on. It is cheaper for manu- 

 facturers using only a small quantity of power to purchase 

 than to produce it ; but there is a point where, from the 

 amount required, it becomes more economical to produce than 

 to purchase. In Belfast, perhaps from the fact that fuel is 

 dearer than in towns in England and Scotland adjacent to col- 

 lieries, or perhaps from the shrewdness of the mill-owners, more 

 care is exercised in the economical production of steam-power 

 than in any other town of the three kingdoms. Even in London, 

 where fuel is dearer, the cost of the production of power is far 

 more than proportionately greater. Mr. Wilson then showed 

 by means of a blackboard the proportionate cost of steam-power 

 per year power units in London, Birmingham, Glasgow, and 

 Belfast. From this it appeared that in London the cost per 

 horse-power per annum for engines of six hundred horse- 

 power ranges from £4 15s. 6d. to £7 7s., in Birmingham 

 from ^*3 13s. to £5 us. 2d., in Glasgow from^*2 14s. to £$ 8s., 

 and in Belfast from £2 10s. to £4 6s. He pointed out how 

 rapidly the cost proportionately increases with the decrease of 

 the amount produced. For instance, the year power unit — 

 that is to say, the cost of one horse-power for three hundred 

 hours — in small engines of 25 horse-power and under frequently 



