August 31, 191 1] 



NATURE 



287 



a year. If, however, the elements which we have 

 used to consider as permanent are capable of chang- 

 ing with evolution of energy, if some form of catalyser 

 could be discovered which would usefully increase their 

 almost inconceivably slow rate of change, then it is not 

 too much to say that the whole future of our race would 

 be altered. 



The whole progress of the human race has indeed been 

 due to individual members discovering means of concen- 

 trating energy and of transforming one form into another. 

 The carnivorous animals strike with their paws and crush 

 with their teeth ; the first man who aided his arm with a 

 stick in striking a blow discovered how to concentrate his 

 small supply of kinetic energy ; the first man who used a 

 spear found that its sharp point in motion represented a 

 still more concentrated form ; the arrow was a further 

 advance, for the spear was then propelled by mechanical 

 means ; the bolt of the crossbow, the bullet shot forth by 

 compressed hot gas, first derived from black powder, later 

 from high explosives, all these represent progress. To 

 take another sequence : the preparation of oxygen by 

 Priestley applied energy to oxide of mercury in the form 

 of heat ; Davy improved on this when he concentrated 

 electrical energy into the tip of a thin wire by aid of a 

 powerful battery, and isolated potassium and sodium. 



Great progress has been made during the past century in 

 effecting the conversion of one form of energy into others 

 with as little useless expenditure as possible. Let me 

 illustrate by examples : A good steam engine converts about 

 one^-ighth of the potential energy of the fuel into useful 

 work ; seven-eighths are lost as unused heat and useless 

 friction. A good gas engine utilises more than one-third 

 of the total energy in the gaseous fuel ; two-thirds are 

 uneconomical!}' expended. This is a universal proposition ; 

 in order to effect the conversion from one form of energy 

 into another, some energy must be expended uneconomic- 

 ally. If A is the total energy which it is required to 

 convert, if B is the energy into which it is desired to 

 convert A, then a certain amount of energy, C, must be 

 expended to effect the conversion. In short, A = B + C. It 

 is eminently desirable to keep C, the useless expenditure, 

 as small as possible ; it can never equal zero, but it can 

 be made small. The ratio of C to B (the economic 

 coefficient) should therefore be as large as is attainable. 



The middle of the nineteenth century will always be 

 noted as the beginning of the golden age of science, the 

 epoch when great generalisations were made, of the 

 highest importance on all sides, philosophical, economic, 

 and scientific. Carnot, Clausius, Helmholtz, Julius Robert 

 Mayer abroad, and the Thomsons, Lord Kelvin and his 

 brother James, Rankine, Tait, Joule, Clerk Maxwell, and 

 many others at home, laid the foundations on which the 

 splendid structure has been erected. That the latent 

 energy of fuel can be converted into energy of motion by 

 means of the steam engine is what we owe to Newcomen 

 and Watt ; that the kinetic energy of the fly-wheel can be 

 transformed into electrical energy was due to Faraday, and 

 to him, too, we are indebted for the re-conversion of 

 electrical energy into mechanical work ; and it is this power 

 of work which gives us leisure, and which enables a small 

 country like ours to support the population which 

 inhabits it. 



I suppose that it will be generally granted that the 

 Commonwealth of Athens attained a high-water mark in 

 literature and thought which has never }'et been sur- 

 passed. The reason is not difficult to find ; a large pro- 

 portion of its people had ample leisure, due to ample 

 means ; they had time to think and time to discuss what 

 they thought. How was this achieved? The answer is 

 simple : each Greek Freeman had, on an average, at least 

 five helots who did his bidding, who worked his mines, 

 looked after his farm, and, in short, saved him from 

 manual labour. Now we in Britain are much better off ; 

 the population of the British Isles is in round numbers 

 45 millions ; there are consumed in our factories at least 

 50 million tons of coal annually, and " it is generally 

 agreed that the consumption of coal per indicated horse- 

 power per hour is, on an average, about 5 lb." (Royal 

 Commission on Coal Supplies, Part I.). This gives seven 

 million horse-power per year. How many man-power are 

 equal to a horse-power ? I have arrived at an estimate 



thus : A Bhutanese can carry 230 lb. plus his own weight, 

 in all 400 lb., up a hill 4000 feet high in eight hours ; 

 this is equivalent to about one twenty-fifth of a horse- 

 power ; seven million horse-power are therefore about 175 

 million man-power. Taking a family as consisting, on the 

 average, of five persons, our 45 millions would represent 

 nine million families, and dividing the total man-power 

 by the number of families, we must conclude that each 

 British family has, on the average, nearly twenty " helots " 

 doing his bidding, instead of the five of the Athenian 

 family. We do not appear, however, to have gained more 

 leisure thereby ; but it is this that makes it possible for 

 the British Isles to support the population which it does. 



We have in this world of ours only a limited supply of 

 stored-up energy, in the British Isles a very limited one — 

 namely, our coalfields. The rate at which this supply is 

 being exhausted has been increasing very steadily for the 

 last forty years, as anyone can prove by mapping the data 

 given on p. 27, table D, of the General Report of the 

 Royal Commission on Coal Supplies (1906). In 1S70 no 

 million tons were mined in Great Britain, and ever since 

 the amount has increased by three and a third million 

 tons a year. The available quantity of coal in the proved 

 coalfields is very nearly 100,000 million tons ; it is easy to 

 calculate that if the rate of working increases as it is 

 doing, our coal will be completely exhausted in 175 years. 

 But, it will be replied, the rate of increase will slow 

 down. Why? It has shown no sign whatever of slacken- 

 ing during the last forty years. Later, of course, it must 

 slow down, when coal grows dearer owing to approaching 

 exhaustion. It may also be said that 175 years is a long 

 time ; why, I myself have seen a man whose father fought 

 in the '45 on the Pretender's side, nearly 170 years ago ! 

 In the life of a nation 175 years is a span. 



This consumption is still proceeding at an accelerated 

 rate. Between 1905 and 1907 the amount of coal raised 

 in the United Kingdom increased from 236 to 26S million 

 tons, equal to six tons per head of the population, against 

 three and a half tons in Belgium, two and a half tons in 

 Germany, and one ton in France. Our commercial 

 supremacy and our power of competing with other 

 European nations are obviously governed, so far as we 

 can see, by the relative price of coal ; and when our prices 

 rise, owing to the approaching exhaustion of our supplies, 

 we may look forward to the near approach of famine and 

 misery. 



Having been struck some years ago with the optimism 

 of my non-scientific friends as regards our future, I sug- 

 gested that a committee of the British Science Guild 

 should be formed to investigate our available sources of 

 energy. This Guild is an organisation, founded by Sir 

 Norman Lockver after his tenure of the Presidency of this 

 Association, for the purpose of endeavouring to impress on 

 our people and their Government the necessity of view- 

 ing problems affecting the race and the State from the 

 standpoint of science ; and the definition of science in this, 

 as in other connections, is simply the acquisition of know- 

 ledge, and orderly reasoning on experience already gained 

 and on experiments capable of being carried out, so as to 

 forecast and control the course of events, and, if possible, 

 to apply this knowledge to the benefit of the human race. 



The Science Guild has enlisted the services of a number 

 of men, each eminent in his own department, and each 

 has now reported on the particular source of energy of 

 which he has special knowledge. 



Besides considering the uses of coal and its products, and 

 how they may be more economically employed, in which 

 branches the Hon. Sir Charles Parsons, Mr. Dugald Clerk, 

 Sir Boverton Redwood, Dr. Beilby, Dr. Hele-Shaw, Prof. 

 Vivian Lewes and others have furnished reports, the 

 following sources of energy have been brought under 

 review : the possibility of utilising the tides : the internal 

 heat of the earth ; the winds ; solar heat ; water-power ; 

 the extension of forests, and the use of wood and peat as 

 fuels ; and, lastly, the possibility of controlling the un- 

 doubted, but almost infinitely slow, disintegration of the 

 elements, with the view of utilising their stored-up energy. 



However interesting a detailed discussion of these possible 

 sources of energv might be, time prevents my dwelling on 

 them. Suffice it to say that the Hon. R. J. Strutt has 

 shown that in this country, at least, it would be impractic- 



NO. 2183, VOL. 87] 



