November 6, 1919] 



NATURE 



241 



by British electricians. In connection with 

 telephony, enormous inventive thought has been 

 given since 1880 to perfecting the mechanism of 

 telephone exchanges, and the diHiculties of auto- 

 matic exchanges, which require no telephone girls 

 or operators to effect the connection between sub- 

 scribers, have now been finally overcome. Another 

 very great advance has been in the "loading " of 

 telephone lines. In 1887 Oliver Heaviside first 

 showed the importance of inductance in the line 

 as a remedy for " distortion " in the wave form 

 of the speech currents, but it was not until Pupin, 

 in the United States in iSgg, suggested the 

 insertion of inductance or " loading " coils at 

 certain proper intervals in the line that practical 

 success was obtained. A Danish engineer, 

 Krarup, introduced a system of uniform loading 

 for submarine telephone lines. The Pupin type 

 of loading has made telephony possible over very 

 great distances, such as New York to San Fran- 

 cisco, and Berlin to Rome. The difficulties of 

 loading submarine cables up to 100 miles or so 

 in length have been overcome. The theory of 

 the subject has been treated by Heaviside, Ken- 

 nelly, and Fleming. 



Wireless telegraphy has attracted the attention 

 of electricians since 1842, but no important inven- 

 tion was made until Marconi in 1896 first showed 

 how to employ electromagnetic waves for this 

 purpose, generated by a special form of Hertzian 

 oscillator, and detected by an improved form of 

 Branly metallic filings coherer. Lodge then 

 demonstrated the importance of syntony in con- 

 nection with the subject, and it soon took very 

 practical shape. Inventors all over the world 

 were attracted to this new field, with the result 

 that in a few years, chiefly by the work of Mar- 

 coni and his co-workers, electric wave telegraphy 

 between ships and shore became established as 

 an indispensable aid to navigation. The con- 

 struction of long-distance wireless stations, the 

 first of which was erected at Poldhu, in Cornwall, 

 in 1 90 1, brought to notice many remarkable facts 

 in connection with the propagation of long elec- 

 tric waves round the earth and through the atmo- 

 sphere. 



A very important factor in the recent develop- 

 ments of wireless telegraphy and telephony has 

 been the invention of the thermionic detector and 

 oscillator. The pioneer invention, according to 

 judicial decisions, was made by the writer of this 

 article in 1904 in applying for the first time an 

 incandescent electric lamp with a metal plate 

 sealed into the bulb as a detector of high- 

 frequency electric oscillations. The "Fleming 



valve " led to the invention of the three-electrode 

 amplifier and thermionic generator of oscillations. 

 This has given us an instrument of marvellous 

 sensibility for detecting electric waves, and made 

 wireless telephony a success and wireless tele- 

 graphy half round the world an achievement. The 

 importance of wireless telegraphy and telephony 

 in the European War of 1914-18 has been the 

 cause of wonderful developments of the subject 

 owing to the number of able minds brought to 

 bear upon it. 



Turning, then, from the present and the past 

 and directing our gaze upon the future, we can 

 certainly see many achievements looming before 

 us. The world will be covered with long-distance 

 wireless stations which will effect instantaneous 

 communication over thousands of miles. Long- 

 distance wireless telephony will enable speech to 

 be transmitted over great distances, and it is 

 quite within the bounds of possibility that the 

 business man of the near future in London may 

 hold a five-minutes' conversation with a friend in 

 New York or even South Africa with as much 

 ease as we now telephone to Glasgow or Liver- 

 pool. Directional wireless telegraphy will be used 

 to steer passenger-carrying aeroplanes through 

 cloud or fog. The steam locomotive and engine 

 will gradually be replaced by the electric motor, 

 and the water-power of the world will be utilised by 

 its means. There are large possibilities still latent 

 in connection with electro-chemistry and electro- 

 metallurgy, and one great problem of the future • 

 is to tap the illimitable stores of energy latent in 

 every chemical atom for the use and benefit of 

 man. As coal becomes exhausted or coal power 

 is made too expensive by labour difficulties, the 

 question of new sources of energy becomes press- 

 ing. The engine of the future may be an im- 

 proved form of internal-combustion engine in 

 which the combustible is not coal gas or oil 

 vapour, but some form of explosive compound 

 in which atomic energy is suddenly relea.sed and 

 expended in heating air or other gas in a cylinder. 



Of one thing we may be perfectly certain, 

 namely, that it is only through the avenue of pure 

 scientific research sedulously and disinterestedly 

 pursued that we shall reach the solution of these 

 technical problems of supreme importance to man- 

 kind. The last fifty years has been a period of 

 extraordinary technical applications of ever- 

 increasing electrical knowledge, and no one can 

 see reason to think that we have yet reached 

 finality in the possible utilisation of this physical 

 agent for ameliorating the conditions of human 

 life. 



DEVELOPMENTS OF MECHANICAL SCIENCE 



Bv Dr. W. C. Unwik, F.R.S. 

 'T'HE attempt here made to give a sketch of 

 -*■ the mechanical side of progress in the last 

 fifty years is necessarily slight. The year 1869 

 was the centenary of that in which Boulton and 

 Watt took out their first patent for the steam 

 NO. 2610, VOL. 104] 



engine. It is due to the application of steam- 

 power to industrial operations, more than to any- 

 thing else, that there has been so great an increase 

 of population, of wealth, and of social prosperity, 

 and indirectly also of scientific knowledge, during 



