206 



DISCOVERY 



tribute in public spheres to the government of the 

 commonwealth it would be natural to find their names 

 at least upon the books of the more catholic of the Inns 

 of Court in the same way that royal and noble per- 

 sonages, soldiers, sailors, statesmen, ecclesiastics, 

 dramatists, poets, politicians, novelists and journalists, 

 and many others, are included among the eminent 

 members of the Middle Temple. Whether in due 

 course the women will undertake the practice of the law 

 is quite another matter. In the search for precedents 

 of women occupying themselves in public spheres there 

 appears to be onlj' one of awoman acting as an advocate, 

 when Lady Crawford appeared in 1563 before the Court 

 of Session in Scotland on behalf of a prisoner indicted 

 for manslaughter {Scots Law Times, February 9, 

 1901, p. 126). It is not the present purpose to dis- 

 cuss the auguments for and against that course, but 

 merely to draw the distinction between admission to 

 an Inn of Court and the possession of the necessary 

 quahfications to practise as a barrister, and still more 

 to attain success in that profession. 



As the result of the passing of the Act a number 

 of other professions have opened their doors to women. 

 Whether the change in the legal status of women thus 

 effected at the beginning of 1920 will form a landmark 

 in the advancement of the common weal is a matter 

 upon which this generation cannot form a judgment. 

 But at least the Act is the legislative record of a national 

 tribute to the noble work done by women in a great 

 period of stress and strain and a desire not to debar 

 any one of the se.\ from a sphere in which conceivably 

 she may find some further opportunity for service. 



How Wireless Signals are 

 Received 



By Lt.-Col. C. G. Crawley, M.I.E.E. 



The ether oscillations which form the waves used in 

 wireless telegraphy are produced by currents of 

 electricity oscillating backwards and forwards at very 

 high speeds, of the order of hundreds of thousands of 

 times a second. These currents, called oscillatory or 

 high-frequency alternating currents, are caused to flow 

 in an elevated w'ire or sj'stem of wires called the aerial, 

 or antenna, from which the wireless waves are radiated 

 into space in all directions. Energy is thus transmitted 

 from the sending station at the same speed as the energy 

 which produces the sensation of light, that is at about 

 186,000 miles a second, but in this case the ether 



oscillations are much slower than in the case of light 

 waves. 



These wireless waves, which are produced by oscil- 

 latory currents, have the property of producing exactly 

 similar currents in any electrical conductor which they 

 meet, and it is this property which is used in the 

 reception of wireless signals. 



In wireless telegraphy, by means of a signalling 

 key at the transmitting station, series of ether waves 

 are sent out for shorter or longer periods of time, that is 

 as dots or dashes, and produce oscillatory currents 

 w'hich continue to flow for the same periods in any 

 conductor which they meet. At the receiving station, 

 as at the sending station, the conductor takes the form 

 of a system of aerial wires ; and to read signals in the 

 Morse Code, the currents produced in the receiving 

 aerial are made to actuate electrical apparatus in such 

 a way as to produce the dots and dashes as marks on 

 paper, or as sounds in a telephone receiver. 



In wireless telephony, the procedure is very much 

 the same, except that the oscillatory currents in 

 the transmitting aerial, and consequently the waves 

 radiated, are modified in strength by the voice in a 

 similar way to that in which the currents are modified 

 in land line telephony. The waves, so modified, 

 produce in the receivdng aerial exactly similar currents 

 which actuate apparatus for producing the voice sounds 

 in a telephone receiver. 



The strength of the currents in the receiving aerial 

 will, of course, depend on the distance away of the send- 

 ing station, since the ether oscillations become weaker 

 and weaker as the distance over which the waves travel 

 increases. A powerful sending station is one in which 

 large currents are produced in the aerial, these currents 

 producing strong ether oscillations which allow of the 

 resulting waves being detected by receiving stations at 

 great distances. Signals from the most powerful 

 European stations can sometimes be read even in 

 New Zealand, but efficient communication over these 

 very long distances is not yet a practical proposition. 



The Marconi Company's station at Carnarvon is 

 the most powerful one in this countrj'. and com- 

 municates as a rule with stations on tlie other side 

 of the Atlantic, such distances, 2.000 to 3,000 miles, 

 being the greatest over which regular communication 

 is at present conducted. However, a French Govern- 

 ment station at Bordeaux, which was designed and 

 partly constructed by the American Army during the 

 war, is very nearly completed, and will ha\e more than 

 twice the available power of any station now in opera- 

 tion. 



In these large stations, separate aerials are used for 

 sending and receiving; in fact, the recci\-ing station is 

 usually some miles away from the sending station, so as 

 to allow of arrangements being made for duplex 



