102 THE ADDRESSES, LECTURES, ETC., OF 



reduce that consumption by 50,000,000 tons. The realisation 

 of such an economy would certainly involve a very considerable 

 expenditure of capital and must be a work of time ; but what 

 I contend is, that our progress in effecting economy ought to be 

 accelerated, in order to establish a balance between the present 

 production and the ever increasing demand for the effects of 

 heat. 



In looking through the statistical returns of the progressive 

 increase of population, of steam power employed, and of produc- 

 tion of iron and steel, &c., I find that our necessities increase 

 at a rate of not less than 8 per cent, per annum, whereas our 

 coal consumption increases only at the rate of 4 per cent., 

 showing that the balance of 4 per cent, is met by what may 

 be called our "intellectual progress." Now, considering the 

 enormous margin for improvement before us, I contend that we 

 should not be satisfied with this rate of intellectual progress 

 involving, as it does, an annual deficit of 4,000,000 tons to be 

 met by increased coal production, but that we should bring our 

 intellectual progress up to the rate of our industrial progress, 

 by which means we should make the coal production nearly a 

 constant quantity for several generations to come. By that 

 time our successors may be expected to have effected another 

 great step in advance towards the theoretical limit of effect, 

 which, as we have seen, lies so far above any actual result we 

 have as yet attained, that an annual consumption of 10,000,000 

 tons would give more than the equivalent of the heat energy 

 which we actually require. 



SOLAE HEAT. 



I have endeavoured to show, in the early part of this lecture, 

 that all available energy upon the earth, excepting the tidal 

 wave, is derived from the sun, and that the amount of heat 

 radiated year by year upon our earth, could be measured by 

 the evaporation of a layer of water 14 feet deep, spread over 

 the entire surface, which again would be represented by the 

 combustion of a layer of coal 8 inches in thickness, covering 

 our entire globe. It must, however, be taken into account that 

 three-fourths of this heat is intercepted by our atmosphere, and 



