1921 .] 
Birks.—Electric-power Load-curves. 
183 
the maximum recorded individual peak loads on the whole of the fifty- 
seven stations in New Zealand for the year ending the 31st March, 1920, 
was 39,416 kilowatts. This curve therefore represents 82 per cent, of the 
recorded maximum electric-power output in New Zealand, and may therefore 
be taken as representative of what will be the average demand of each 
interconnected system under the present selling-rates. The combined peak 
load is 25,305 kilowatts—that is, 60-2 per cent, of the installed capacity 
in the above fourteen stations—the balance, 16,750 kilowatts, being reserve 
capacity. The load-factor of the combined curve for the day—that is, 
the ratio of the average to the maximum load—is 68 per cent., and is thus 
very high indeed even under existing selling-conditions. With larger hydro¬ 
electric power-supply sources, and economies not possible from steam 
generating-stations, it is probable that this daily load-factor will be 
increased to a slightly higher figure. But in the meanwhile the composite 
load-curve shown in the figure may be accepted as typical of New Zealand 
conditions generally, and may be taken as a basis on which to determine 
the costs and necessary revenue per unit from any large developments 
which are anticipated in the Dominion. For comparison arrangements are 
being made for the preparation of a similar composite curve for mid-winter 
conditions this year. 
I have to express my thanks to Mr. M. H. Millar, P Assistant Electrical 
Engineer, Public Works Department, for preparing the data on which the 
curve is based. 
EFFECTS OF THE RECENT AURORA ON TELEGRAPH- 
LINES, TELEPHONE - LINES, AND WIRELESS 
STATIONS. 
By A. Gibbs, M.l.E.E. 
Disturbances to which Telegraph-lines, Telephone-lines, and Wire¬ 
less Stations are Subject. 
Telegraph and telephone circuits and wireless receiving-apparatus are 
peculiarly sensitive to disturbances by adjacent electrical circuits and by 
certain natural phenomena. They are not all affected to the same extent, 
for they are not equally influenced by the various disturbing causes ; and, 
moreover, the sensitivity of the apparatus employed in the different 
systems varies considerably. 
Land Telegraph-lines. 
Land telegraph-lines are to a large extent immune from many of the 
disturbances that would prejudicially affect either wireless reception or 
the operation of certain telephone circuits. This is due partly to the 
different system of reception employed, but mainly on account of the lower 
sensitivity of telegraph receiving-instruments, some of which operate with 
currents a thousand times as great as those required in telephone work, 
and a million times as great as those dealt with in radio receiving-apparatus. 
In some countries, however, where high-tension power-transmission and 
