1921 .] 
Gibbs.—Effects of Recent Aurora. 
185 
tramway system has a marked effect upon these testing operations, causing 
variations in the electrical potential of the earth, which, in a somewhat 
similar manner to natural electrical and magnetic phenomena, cause 
extraneous earth currents to flow through the delicate testing-apparatus. 
Wireless Stations. 
In the realm of wireless telegraphy and telephony we are brought into 
very serious contact with the disturbing effects produced by the invisible 
forces of nature. Modern wireless receiving-apparatus is remarkably sensi¬ 
tive, and considerable care has to be taken in the design and location of a 
wireless station in order that its work may not be unduly interfered with 
by natural or artificial causes, which would reduce the efficiency of the 
station. The natural disturbances with which a wireless station has more 
usually to combat are known indifferently as “ atmospherics,” “ statics,” 
“ strays,” or, more popularly, “ X’s.” They are the result mainly of 
electrical discharges in the atmosphere, which produce in the ether natural 
electrical waves. They are very erratic, are subject to diurnal and seasonal 
variations, and are influenced by varying meteorological conditions. These 
ever-present phenomena manifest themselves in the form of noises of all 
descriptions in the wireless telephone receivers. At times this is so severe 
as effectively to interrupt wireless communication by entirely drowning the 
received signals. This is more marked in the tropics, where at times for 
considerable periods wireless services are paralysed from this cause. In 
tropical localities a coming thunderstorm is notified to the wireless operator 
well in advance by a “ patter ” of electrical disturbances not unlike the 
sound of falling rain; and at Rarotonga the presence of heavy rain-clouds 
on the top of a mountain that lies in the route of wireless signals coming 
from New Zealand noticeably affects the strength of the signals received 
from this country. “ X’s ” are stronger and more prevalent at night than 
in the daytime ; and for this reason wireless communication between Awanui 
and Samoa, for example, can be carried on with less power during daylight 
hours than during the hours of darkness, despite the fact that in general 
during the hours of daylight signals are considerably reduced in strength 
relatively to the dark hours. A great deal of investigation has been made 
of the nature and origin of “ atmospherics.” Just before the outbreak of 
war the New Zealand wireless service, in conjunction with wireless adminis¬ 
trations throughout the Empire, co-operated in a systematic recording and 
classification of these atmospheric disturbances. This was interrupted 
when war commenced, but it is believed that during the few months in 
which observations were taken many valuable data were collected, enabling 
useful and helpful deductions to be made therefrom. It should perhaps 
be mentioned that the New Zealand Post and Telegraph Department, in 
common with similar departments in other dominions, is now co-operating 
with a recently established Radio Research Board in the United Kingdom, 
which has for one of its objects an investigation into the causes and 
characteristics of atmospherics and the possible elimination of the effects 
they produce upon wireless reception. 
Many devices have already been introduced to minimize the effect- 
of these strays, but a final and satisfactory solution of the problem has 
yet to be reached. It has, however, been definitely established that 
certain of these atmospherics are vertically propagated, and this has sug¬ 
gested a somewhat costly and elaborate remedial process, which is unlikely 
to receive general adoption. When it is considered that the propagation 
