APRIL 2, 1914| NAT OLE iG 
self-extinguishing power of electric arcs produced | frequency alternation it is said that a small 
between certain’ metals which are good conduc- | variation in the exciting current will produce 
tors, such as aluminium and copper. If a pile of | very large variations in the amplitude of the 
plates of these metals with very small air-gaps is | radiated waves. Hence the microphone can 
built up, and a high electromotive force applied | be placed in the excitation circuit, and need 
to it, discharges will take place, or small arcs | only have a current-passing capacity of a 
which, when the discharger is shunted by a con- | few amperes to be able to modulate a_ radia- 
denser, can generate high-frequency oscillations. | tion representing a very large horse-power. 
By the aid of these appliances, their inventors and | To transmit articulate speech across the 
other workers have conducted wireless telephony | Atlantic will necessitate the power of varying 
up to a distance of 1000 kilometres, or, say, five | the amplitude of continuous wave radiation repre- 
hundred or six hundred miles. | senting at least 50 or 100 horse-power. This must 
Thus, Dr. J. Vanni, working at Rome, and | be done by means of some microphone which 
using a Moretti arc generator, his own liquid | passes not more than, say, 10 amperes. These 
microphone, and a form of Fleming oscillation | conditions are not impossible of attainment. 
valve as a receiver, has transmitted and received | Hence Transatlantic wireless telephony may be 
articulate speech between Rome and: the Island | said to be within the range of practical politics, 
of Ponza (120 km.), to Maddalena (260 km.), to | whilst no improvements yet made in submarine 
Fic. 3.—Dubilier water-cooled large current microphone. 
Palermo (420 km.), to Vittoria (600 km.), and telephonic cables hold out hope of being able 
finally between Rome and Tripoli, a distance of | within any reasonable time to speak through an 
1ooo km. Atlantic cable. 
The speech is said to have been clear and singu- The subject of wireless telephony is, therefore, 
larly free from evidence of distortion of wave one which holds out much promise for future 
form. In addition to this, successful experi- achievement, and it is not surprising that it is 
ments in wireless telephony are said to have been attracting the attention of some of the leading 
conducted between Berlin and Vienna, a distance workers in radiotelegraphy. J. A. FLEMING. 
of 375 miles, by the Telefunken Company. The 
stations were the German high-power station at A BIRD WITH A HISTORY.! 
Nauen, to the west of Potsdam, and a receiving 
station on the roof of the Technological and In- 
dustrial Museum at Vienna. The experiments 
were sO promising that it is expected much 
greater distances can be covered. A very invit- 
ing field of work seems to | ening out in : ara Us 
S . . Rae 2 history, at times among the publications of 
connection with the alternator method of genera- it cit ; ‘ : li 
4 =e " ; 3 é 1 ‘‘The Gannet: A Bird with a History.” By J. H. Gurney. Pp. lit+ 
tion. With a suitably designed Goldschmidt high- __ .67+plates. (London: Witherby and Co., 1913.) Price 27s. 6d. net. 
NO. 2318, VOL. 93] 
WELL-KNOWN ornithologist here gives us 
the fruits of many years of careful study 
devoted to a single species. His study has been 
diverse: at times it has lain among etymological 
dictionaries and curious old works on_ natural 
