274 W. E. AND F. JB. COOKE. 



the latest forms of oscillating Audion receivers. In our 

 opinion this combination is greatly superior, for several 

 reasons. In the spark system no current passes until the 

 key is closed, and then some little time must elapse before 

 radiations actually commence. In the arc system the 

 current is flowing through the aerial continuously, and the 

 action of pressing the key simply shorts a few turns of wire 

 in the inductance and thus alters the wave length. It is 

 quite probable, though we have not yet had the opportunity 

 of testing the question, that very short sharp dots can be 

 sent by this method, if required, 



Then again, the tuning of the arc can be made far sharper 

 than the spark, and the Audion is very much more sensitive 

 than the crystal. E.g., with our little aerial at the Obser- 

 vatory we have no difficulty in hearing Tuckerton (New 

 Jersey) at a distance of about 10,000 miles. It would be 

 a simple matter to choose some wave length sufficiently 

 distinct to be free from interference, and to tune sharply, 

 so that we should hear nothing except the time signals and 

 the atmospherics. 



Finally the receiving observer makes his own "tune." 

 That is, he can control the oscillation of his Audion so as to 

 bring the signals to any musical pitch he desires, and by ' 

 raising this sufficiently he can cause such a difference 

 between the sound of the dots and the lower growl of the 

 atmospherics, as to very considerably reduce the annoyance 

 from the latter. 



(3) The main principle can easily be used for the com- 

 parison of local clocks or chronometers, in particular for 

 comparing mean and sidereal times. In this case the mean 

 time clock takes the place of c, and the sidereal of r , and 

 the latter instead of being in series with the aerial, is 

 placed in series with a battery and high-pitch buzzer. With 

 this arrangement not only can coincidences be obtained 



