TRANSACTIONS OF SECTION A, 401 
3. On the Discharge of Ultra-violet Light of High-speed Electrons. 
By Professor R. A. Mipnican. 
The ultra-violet light emanating from a spark source is able under suitable 
conditions to impart to electrons an initial velocity of at least 500 volts, while 
the velocities imparted under the same circumstances by a quartz-mercury lamp 
are never found to exceed 6 volts. 
_ An explanation of this difference is sought in the enormous instantaneous 
intensity of the light from a spark source, notwithstanding the fact that previous 
work has seemed to show an independence of initial velocity and intensity. 
4. The Presence of Radium in the Chromosphere. 
By F. W. Dyson, F.B.S. 
5. The Number of the Stars, and their Bearing on Stellar Distribution. 
By Dr. §. Cuapman. 
6. The Law of Equivoluminal Oscillations in Metals. 
By Professor W. Peppi. 
FRIDAY, SEPTEMBER 6. 
Discussion on the Scientific Theory and Outstanding Problems of 
Wireless Telegraphy. 
(i) Introductory Remarks. By Professor J. A. Fuemina, D.Sc., F.R.S. 
The chief object of this discussion being to consider matters of great scientific 
interest in connection with wireless telegraphy which are still imperfectly ex- 
plained, a brief description may first be given of the usual apparatus of radio- 
telegraphy in the large majority of stations due to the inventions of Marconi, 
Lodge, and many others. Apart from Marconi’s improvements in the metallic 
filings coherer of Hughes, Branly, and Lodge, the important element in the 
arrangements by which in 1896 he applied purely scientific knowledge of Hertzian 
electric waves to practical electric wave or radio-telegraphy was the introduction 
of the long, nearly vertical, aerial wire as a radiator, combined with a metal 
plate above or buried in the earth as the balancing capacity. In this wire, 
high-frequency oscillations are created ; originally by using the wire itself as one 
electrode of an air-condenser and the earth as the other, but later on by inducing 
oscillations in the wire by means of the dead-beat or oscillatory discharge in 
another condenser circuit including a spark-gap coupled to the air wire-circuit. 
Although enormous ingenuity has been expended in improving or varying every 
element in the appliances, we can say that, with the exception of a small number 
of stations using the Duddell-Poulsen arc generator, nearly all the practical wire- 
less telegraphy in the world is at present (1912) conducted by the following 
apparatus. At each station there is a transmitter which comprises three 
elements :— 
1. A source of high E.M.F. which may be a continuous-current dynamo 
and storage battery, an alternator and transformer, or a battery and 
induction coil giving continuous, alternating, or interrupted high- 
tension E.M.F, 
2. A condenser in which the generator stures an electric charge to be 
suddenly released when a certain potential is attained across a spark- 
gap in the form of an electric discharge passing through a coil in 
series with the condenser. 
1912. DD 
