90 



NATURE 



[September 15, 192 1 



occur during the time that every sound-wave 

 lasts, and by letting them control a crowd of elec- 

 trons in an exhausted vessel or vacuum tube their 

 intensity can be controlled by every ripple, every 

 rustle, every shock, and every sibilant which go 

 to constitute human speech ; and the radiation 

 emanating from the electric oscillations will then 

 be graduated in intensity so that the waves which 

 travel in the aether shall be strong or weak exactly 

 as the stimulus requires. 



Receive the electric waves and convey them to 

 another empty bulb containing again a hot wire 

 giving off electrons ; the crowd of particles 

 respond, another current is generated, carved into 

 fluctuations of corresponding strength, and these 

 variations of current, when employed to actuate 

 a telephone, can accurately reproduce the tones of 

 the distant voice. 



Roughly and generally that is the plan, and 

 the astonishing feat is carried out by various in- 

 genious devices. I was not specially astonished 

 by the wireless transmission of coarse signals 

 like the dot and dash of ordinary telegraphy. It 

 is no more diflficult to send impulses across space 

 than to guide them by wires. What Mr. Marconi 

 has made practical as "wireless" might have 

 come in first, and then wires might have been 

 regarded as an improvement, like speaking 

 through a tube instead of shouting into the open 

 air. Any mechanical sending key and many a 

 mechanical relay can accomplish that, but no 

 mechanical relay could follow the variations of 

 quality in human voice ; no agency short of the 

 electron would be quick and docile enough ; but 

 with their aid the feat is accomplished, and the 

 electric waves which act as the intermediary can 

 travel a thousand miles or more before being 

 received and once again transmuted. 



One more principle I must emphasise. How 

 can the human ear or any instrument follow vibra- 

 tions of millions a second? It cannot. Only the 

 electron can do that. But suppose that, in addi- 

 tion to the oscillations coming from a distant 

 station, we set up home oscillations in a small 



subsidiary vacuum tube of nearly the same fre- 

 quency. Let the incoming waves vibrate a million 

 times, for instance, while our local arrangement 

 vibrates a million plus 500. What will happen ? 

 They will "beat." They will give 500 beats a 

 second, and that is a musical note. To that we 

 can listen, and upon that the variations of in- 

 tensity can be superposed. 



This is not the first plan adopted. The first 

 plan was the utilisation of crystals and other 

 detectors, such as the Fleming valve, to rectify 

 the oscillation, to check all the negative pulses 

 and utilise all the positive, to let only one sign 

 through. Thus we got the vacuum valve. But 

 soon this was improved by Lee Forest into a 

 magnifier, so that an original impulse, exceedingly 

 weak, could be strengthened a hundred or even a 

 thousand times by using the electrons as relays 

 and putting a number of relays in series. 



So also for transmitting, the magnifying device 

 is available. The electric impulses from the first 

 valve, the one directly actuated by the microphone 

 —these need not be given to the aether ; they can 

 be used to stimulate another valve, so as to 

 increase their intensity until the waves generated 

 are powerful enough to be allowed to rush across 

 the Atlantic. This they are able to do in a frac- 

 tion of a second. And there, though what arrives 

 is only a feeble residue, since they have spread 

 far and wide by that time, yet they preserve all 

 their peculiarities intact, every pulse of the speech 

 is retained and can be reproduced, and by 

 adequate magnification can be made easily 

 audible. 



Distance is no deterrent ; it only enfeebles ; it 

 does not confuse and spoil, as it does with a wire 

 embedded in the ocean. The properties of the 

 aether are perfect, and all the fluctuations are 

 accuratelv conveyed. All that we require is a 

 magnifier to get a convenient intensity, and that 

 the ingenuity of man has supplied. We have 

 learnt to communicate eflficiently across space void 

 of matter. Possibilities are thus opened up th( 

 end of which no man can foresee. 



I 



Variations of Climate since the Ice Age.^ 



By C. E. P. Brooks. 



THHE nineteenth century envisaged the Ice age 

 *■ as a remote catastrophe, sharply separated 

 from the changeless present. The past twenty 

 years have reversed that view ; geologists and 

 botanists have traced considerable fluctuations of 

 temperature and rainfall extending from the last 

 (Wiirmian) glacial period into historical times, 

 while archaeologists, working backwards from the 

 present, have met them at the dawn of history with 

 conditions appreciably different from those of 

 to-day. In the countries bordering on the North 

 Atlantic at least, the facts have been laid down 

 with security, and it is now the task of meteoro- 



1 Abridged from a paper in the Quarterly Journal of the Roy»l Meteoro- 

 ogical Society, July, 1921, pp. 173-94. 



NO. 2707, VOL. 108] 



logists to elucidate the various distributions ol 

 pressure and winds which were associated with 

 these changes of climate. 



At the present day the great ice-sheets of Green- 

 land and the Antarctic Continent are occupied by 

 permanent areas of high pressure, and we may 

 infer that the Quaternary ice-sheets of northern 

 Europe and North America were c-ccupied Sy 

 similar anticyclones, with dry easterly winds on 

 their southern borders. In Europe at least there 

 is direct evidence of this in a belt of " fossil 

 dunes " extending from Russia to Holland; these 

 dunes are crescent-shaped with their convexities 

 to the east, indicating that they were formed by 

 easterly winds. The Atlantic must have been a 



