1 88 THE. ADDRESSES, LECTURES, ETC., OF 



itself to us as the all-animating, all-vivifying solar ray, by which 

 our earth is clad, and to which we owe our material existence. 



The coal itself, which yields us so important a supply of energy, 

 is no exception to this rule, being only the result of vegetation in 

 former ages, when the ray of the sun separated carbon from 

 carbonic acid of the atmosphere in the leaves of plants in the same 

 manner in which it does to-day, and thus made for us a store of 

 accumulated carbon, or, metaphorically speaking, of accumulated 

 sunbeams which may be called large, but which, in view of our 

 ever-increasing requirements, must become exhausted, not indeed 

 in our lifetime, but in the lifetime of those who follow us in com- 

 paratively few generations to come. 



According to the Eeport of the Coal Commissioners, published 

 in 1871, there were then nearly 150,000,000,000 of tons of coal 

 available in Great Britain. The present rate of consumption is 

 about 132,000,000 of tons annually, and statistics show that there 

 is a mean annual increase in the output of 3J millions of tons, 

 and a calculation at this rate of increase would give 250 years as 

 the life of our coal-fields. It must be borne in mind, however, 

 that long before the last ton of coal is-brought to the surface, the 

 effect of its gradual failure will have made itself painfully manifest. 

 Districts whose industry is most active and populations largest, 

 will first experience the change, and it behoves us to consider in 

 good time what resources, if any, we shall have to fall back upon. 



I have shown that the universal source of energy is the sun, but 

 there is- one important exception, namely, the force of the tidal 

 wave. This is of cosmical origin, depending upon the acquired 

 rotation of the earth, as influenced by the local attraction exer- 

 cised upon it by the moon and the sun, and, if utilised, would tend 

 to a gradual reduction in the course of ages of the earth's rotative 

 velocity. The amount of available energy represented by this 

 source is vast indeed, but cannot be utilised to a large extent, 

 except in comparatively few localities and at great inconvenience 

 and expense. 



For all practical purposes we depend upon the solar ray past and 

 present for our supply of useful energy, and when we shall have 

 consumed the stores produced in former ages, we must be content 

 to live with it from hand to mouth. This condition of things may 

 satisfy the negro in Central Africa or the agriculturist of Southern 



