1921 .] 
Gibbs.—Effects of Recent Aurora. 
187 
An interesting experiment was performed at Awarua, where during 
the height of the disturbance an insulated counterpoise (or network of 
insulated wires) was substituted for the usual earth connection. In effect, 
the wireless receiving-system was entirely disconnected from the earth, 
and therefore not subject to direct interference from electrical charges 
circulating therein. This removal of the earth connection did not in any 
way affect the prevailing variations of the signals, which continued to be 
as erratic as ever. During the period referred to there were brief intervals 
at all New Zealand stations when signals returned to normal and nothing 
unusual was noticed. 
The effects at New Zealand stations may be summarized as follows : 
(1) Great and sudden variations in signal-strength from maximum to 
minimum ; (2) signals from different directions not simultaneously affected ; 
(3) dead periods when neither signals nor statics were heard ; (4) periods of 
abnormal intensity of signals and statics ; (5) signals from European long¬ 
wave stations unaffected during the whole period. 
All of the New Zealand stations are connected by land telegraph-lines 
with the telegraph centres, and it was noticed at times that great variations 
in radio signals were simultaneously accompanied by earth currents in 
the land telegraph-lines of sufficient intensity to render the Morse circuits 
inoperative. 
Land Telegraph-lines. 
During the auroral period the land telegraph-lines throughout New 
Zealand were subject to abnormal disturbances due to what are technically 
known as “ earth currents.” As previously indicated, these Morse lines 
are operated upon the earth-working principle, and are therefore inherently 
susceptible to fluctuations in the potential of the earth. As in the case of 
the wireless disturbances, the Morse lines all over New Zealand were affected, 
but not necessarily at the same time nor to the same degree. In general 
the interference manifested itself in the form of violent fluctuations of 
current in the telegraph lines and instruments, but in many cases the 
variations in the direction of these foreign currents were slow and gradual, 
although far from uniform in their movements. In some cases the foreign 
voltages were found to be of the order of 60 volts, and were of sufficient 
magnitude to render Morse working by the usual means impossible. At 
the principal centres it was frequently observed that lines running east and 
west were more seriously affected than those running north and south, but 
this experience cannot be said to have been either general or uniform. The 
first indication of anything unusual was noticed at Napier, where on the 
12th and 13th it was observed that the Morse lines were peculiarly affected 
by induced voltages of small magnitude, which rendered the adjustment 
of the apparatus difficult and uncertain. For a few days subsequent to 
the 16th similar effects were observed at this station. The main effects 
were first noticed at all stations upon opening for business at 8 a.m. on 
the 14th. Practically all Morse lines, and especially the longer ones, were 
badly affected by earth currents, and during the 14th, 15th, and 16th the 
longer-distance lines had during the greater part of this period to be worked 
upon the metallic-circuit principle, by which means all connection with 
the earth was removed and a conducting wire substituted for the earth- 
return circuit. 
As an indication that earth currents were not entirely responsible for 
these circumstances, it should be mentioned that on the longer lines even 
the metallic-circuit arrangement did not remove all causes of trouble. The 
atmospheric electrical charges which accompanied the aurora continued to 
