HERTZIAN WAVE WIRELESS TELEGRAPHY. 65 



syntonization of two stations, not by syntonizing the receiver for the 

 exceedingly high frequency oscillations of the individual electric waves, 

 but to syntonize it for the much lower frequency, corresponding to that 

 of the intervals between the groups of waves. Thus, for instance, if 

 an ordinary simple transmitting aerial is set up, the production of 

 sparks between the spark balls results in the emission of short trains 

 of waves, each of which may consist of half a dozen or more individual 

 waves, the time of production of the whole group being very small 

 compared with the interval between the groups. M. Blondel pro- 

 poses, however, to syntonize the receiver, not for the high frequency 

 period of the waves themselves, which may be reckoned in millions 

 per second, but for the low frequency period between the groups of 

 waves, which is reckoned in hundreds per second. Thus, for instance, 

 if sparks are made at the rate of fifty or a hundred per second, they 

 can be made to actuate the telephone receiver and so produce in the 

 telephone a sound corresponding to a frequency of 50 or 100. In other 

 words, to make a low musical note or hmn. This continuous sound 

 can be cut up, by means of a key placed in the primary circuit of the 

 transmitting arrangement, into long or short periods, and hence the 

 letters of the alphabet signal. 



M. Blondel's arrangements comprise a Mercadier's monotone tele- 

 phone and either a coherer or a particular form of vacuum tube as a 

 kumascope. On August 16, 1898, M. Blondel deposited with the Acad- 

 emy of Sciences in Paris a sealed envelope containing a description of 

 his improvements in syntonic wireless telegraphy, which was opened 

 on May 19, 1900.* The arrangement of the receiving apparatus was 

 as follows: A single battery cell keeps a condenser charged until 

 the kumascope is rendered conductive by the oscillations coming down 

 the aerial; and under these circumstances the condenser discharges 

 through the telephone and causes a tick to be heard in it. If the trains 

 of waves are at the rate of 50 or 100 per second, these small sounds run 

 together into a musical note, and this continuous hum can be cut up 

 into long and short spaces, in accordance with the Morse alphabet 

 signals. The telephone must not be an ordinary telephone, capable 

 of being influenced by any frequency, but be one which responds only 

 to a particular note, and under these conditions the receiving arrange- 

 ment is receptive only when the trains of waves arrive at certain 

 regular predetermined intervals, corresponding with the tone to which 

 the telephone is sensitive. 



* See Comptes Rendus, May 21, 1900; Rapports du Congres International 

 d'Electriciti, Paris, 1900, p. 341. 



VOL. liXIV. — 5. 



