January 14, 1909J 



NA TURE 



325 



J. J. Thomson's theory makes its moment of momentum 

 exactly equal to coi, the product of charge and pole, the 

 charge being measured electrostatically and the pole 

 magnetically. 



How can this be shown experimentally? Suppose we 

 had a spinning top enclosed in a case, so that the spin 

 was unrecognisable by ordinary means — it could be de- 

 tected by its gyrostatic behaviour to force. If allowed to 

 " precess " it will respond by moving perpendicularly to 

 a deflecting force. So it is with the charge and the mag- 

 netic pole. Try to move the charge suddenly, and it 

 immediately sets off at right angles. A moving charge 

 is a current, and the pole and the current try to revolve 

 round one another — a true gyrostatic action due to the 

 otherwise unrecognisable ethereal spin. The fact of such 

 magnetic rotation was discovered by Faraday. 



1 know that it is usually worked out in another way, in 

 terms of lines of force and the rest of the circuit ; but I 

 am thinking of a current as a stream of projected charges, 

 and no one way of regarding such a matter is likely to 

 exhaust the truth or to exclude other modes which are 

 equally valid, .\nyhow, in whatever way it is regarded, 

 it is an example of the three rectangular vectors. 



The three vectors at right angles to each other, which 

 may be labelled current, magnetism, and motion re- 

 spectively, or more generally E, H, and V, represent the 

 quite fundamental relation between aether and matter, and 

 constitute the link between electricity, magnetism, and 

 mechanics. Where any two of these are present, the third 

 is a necessary consequence. This principle is the basis of 

 all dynamos, of electric motors, of light, of telegraphy, 

 and of most other things. Indeed, it is a question whether 

 it does not underlie everything that we know in the whole 

 of the physical sciences, and whether it is not the basis 

 of our conception of the three dimensions of space. 



Lastly, we have the fundamental property of matter 

 called inertia, which, if I had time, I would show could 

 be explained electromagnetically, provided the ethereal 

 density is granted as of the order lo'^ grams per cubic 

 centimetre. The elasticity of the scther would then have 

 to be of the order lo" C.G.S., and if this is due to intrinsic 

 turbulence, the speed of the whirling or rotational elasticity 

 must be of the same order as the velocity of light. This 

 follows hydrodynaniically, in the same sort of way as the 

 speed at which a pulse travels on a flexible running endless 

 cord, the tension of which is entirely due to the centri- 

 fugal force of the motion, is precisely equal to the velocity 

 of the cord itself; and so, on our present view, the 

 intrinsic energy of constitution of the tether is incredibly 

 Tnd portentously great, every cubic millimetre of space 

 possessing what, if it were matter, would be a mass of a 

 thousand tons, and an energy equivalent to the output of 

 a million-horse-power-station for forty million years. 



The universe we are living in is an extraordinary one, 

 and our investigation of it has only just begun. We know 

 that matter has a psychical significance, since it can con- 

 stitute brain, which links together the phvsical and the 

 psychical worlds. If anyone thinks that the a'ther, with 

 all its massiveness and energy, has probably no psychical 

 significance, I find myself unable to agree with him. 



SCIENCE AND THE PRACTICAL PROBLEMS 



OF THE FUTURE.' 

 A T the recent conference on the conservation of resources 

 ■^ which met at the White House at the invhation of 

 the President of the United States, notes of warning were 

 sounded concerning the coming exhaustion of coal, wood, 

 ores, and soils. Whether or not we accept as exact the 

 I'stimates furnished by experts on that impressive occasion, 

 (here is no doubt that we are approaching the end of our 

 available resources, and that the near future will have 

 momentous problems to face. 

 Certain things are clear. 



First. — Unchecked wastefulness as exhibited, for ex- 

 ample, in the extermination of the bison, in the destruction 

 of forests, in the exhaustion of the soil, in the disappear- 



' Abridged from the address delivered by Prof. F.. L. Nichols, the retiring 

 liresident of the American Association for the Advancement of Science, at 

 the Baltimore meeting, December, iqo8. 



NO. 2046, VOL. 70] 



ance from our coasts and streams, that once teemed with 

 fish, of this important source of food supply, in the pour- 

 ing into the air of an incredible amount of unused fuel 

 from hundreds of thousands of coke ovens, must cease, or 

 our ruthless exploitation will bring disaster on generations 

 soon to come. The prevention of these and countless other 

 manifestations of individual and corporate greed is a 

 problem for the economist and the law-maker, although 

 they will scarcely succeed in its solution without calling 

 science to their aid. 



Second. — Saving and thrift offer at best only a postpone- 

 ment of the day of distress. The end of our supplies of 

 coal and petroleum must ultimately be reached. Forests 

 may be renewed and the soil restored to its maximum 

 fertility, but the problem which is presently to confront 

 the race is that of civilised existence without recourse to 

 energy stored by the slow processes of nature. This 

 problem must be definitely solved before the complete 

 exhaustion of our inherited capital. 



Third. — The problem is not without conceivable solu- 

 tion, since the annual accession of energy from the sun, 

 did we know how to utilise it without awaiting the slow 

 processes of storage employed by nature, is ample for 

 every thinkable need of the future inhabitants of our 

 planet. Estimates of the constant of solar radiation show 

 that about 2-i8 kilowatts of power is continually received 

 from the sun for every square metre of the earth's surface, 

 or more than seven and a half millions of horse-power per 

 square mile. The present use of power in the United 

 States is about eighty million horse-power, or one horse- 

 power per capita. This quantity is likely to increase more 

 rapidly than the population in the future unless curtailed 

 by lack of fuel, but it is evident that a very small fraction 

 of the sun's radiation would meet all demands. 



Now abundant power is soon to be the factor upon which 

 material advancement will chiefly depend. To obtain it in 

 the face of the disappearance of coal and petroleum will be 

 imperative. For success in this, upon which in the 

 immediate future the welfare of the race and ultimately 

 its very perpetuity is to depend, we must look to science. 

 Mere ingenuity or inventiveness, however widely developed, 

 will not suiilice. The inventor and the engineer can but 

 utilise and apply the material which the man of science 

 provides, and with the exhaustion of our stores of scientific 

 knowledge civilisation must halt. 



It is of this fundamental relation of science to the 

 progress of our civilisation that I wish to speak. The 

 fact that material progress is based upon science seems to 

 be but dimly understood. It appears to be generally sup- 

 posed that it is to the inventor and to those who use his 

 devices that we owe our present advantages over our fore- 

 fathers. I would not belittle the achievements of the so- 

 called practical man, but the public must be taught that 

 application can never run ahead of the knowledge to be 

 applied, and that the only road to higher achievement in 

 practical things is by the further development of pure 

 science. 



The viain product of science, using that word in its 

 broadest sense, is knowledge ; among its by-products are 

 the technological arts, including invention, engineering in 

 all its branches, and modern industry. Not all industries 

 have attained the character of a technological art. Burn- 

 ing the woods to drive out game, and thus obtain a dinner, 

 is a form of industry. Like it in character are some very 

 large industries, such as agriculture of the sort that 

 impoverishes the soil ; lumbering that destroys forests, and 

 incidentally ruins rivers and increases erosion ; coke- 

 making bv processes that waste 40 per cent, of the energy 

 of coal. The production of power from coal by means 

 of the steam boiler and the reciprocating engine we at 

 present regard as a highly developed technological art ; 

 vet it is a process which, at the very best, converts less 

 than 10 per cent, of the total stored energy of the fuel 

 into available form. If the ultimate purpose of this power 

 is the production of light, we by our present methods 

 suffer a second waste of 90 per cent, or more, so that the 

 efficiencv of the combined processes is but a fraction of 

 I per cent. These things are excusable while ignorance 

 lasts. They become criminal with realisation of the results, 

 and are inconceivable in a community of fully developed 

 civilisation. Science paves the way for the gradual sup- 



