Note on the Aurora Australia, as observed at Karori, Wellington, on the 20th August, 1894.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 27, 1894, Page 657

. Papers.—1. “Note on the Aurora Australis, as observed at Karori, Wellington, on the 20th August, 1894,” by G. V. Hudson, F.E.S. Abstract. The author first noticed this aurora at 7 p.m. as a strong whitish light-along the southern horizon, somewhat resembling the earliest traces of the dawn. This light steadily increased, gradually forming itself into a shaded arch, which extended from the south-east to the south-west. Below this arch the sky appeared extremely dark, as if heavily clouded, but this was evidently merely the effect of contrast, because he noticed not only Canopus, but several fainter stars, shining with undiminished brilliancy beneath the arch during the whole of the display. As the aurora progressed the arch gradually rose in the heavens. At 8 p.m. the first bright streamers appeared, and were most numerous to the westward. Above and amongst the streamers were glowing patches of the most beautiful rose-colour. The aurora was now a magnificent spectacle, its light being sufficient to render all the leading features of the landscape clearly discernible, and large print could be read with little difficulty. Shortly before 9 p.m. the dull light of the moon could be seen in the

east-north-east. At this time what appeared to be the beginning of a second arch formed above the original one. It formed with great rapidity in the south-west, extending itself in an easterly direction for a short distance, and then vanished. The moon rose at 9 p.m., but did not appear to have much effect on the brilliancy of the display, until about 9.45 p.m., when the aurora was reduced to an arch of milky haze across the southern sky. Shortly after 10 p.m. there was a second display of streamers, which shot upwards as far as the zenith, where they dissipated in the most brilliant rosy glow. During this last display the arch appeared to become completely disintegrated, and at 10.30 p.m. scarcely a trace of the aurora could be seen. In view of the connection which he understood was generally supposed to exist between auroral displays and sun-spots, he looked at the sun the following morning with a telescope of moderate power, and noticed seven spots, two of which were evidently of very large dimensions. Sir James Hector said the auroral arcs were always at right angles to the magnetic meridian. This meridian, however, is always in motion, vibrating from east to west, but the extent of vibration is much greater during an auroral display, as he had observed during his observatory-work in high latitudes in North America in 1857. In New Zealand the auroral rays converge to N.N.E. of the zenith, and form a crown at 80° altitude from the horizon. As a rule there is disturbance of telegraphic communication coincident with such discharges, so that it must be a terrestrial magnetic as well as an atmospheric electric phenomenon. The height of the discharge has been variously related from as low as house-tops to as high as 1,000 miles; but from fifty to one hundred miles is the result of the most reliable observations. With regard to the connection between auroras and solar storms, the few observations so far indicate that the influence is real, and that the action is almost instantaneous, even exceeding the velocity of light. It resembles a sympathetic action like the “Hertz waves” of radiant electricity traversing the ether. During the last twenty-five years, while he had been in charge of the records, there had been sixty-three auroral displays, of which fifty-two were visible only in the south of New Zealand. Of the eleven seen all over New Zealand, five were simultaneously recorded in Australia and at the Cape of Good Hope. In fourteen of these years none were recorded in New Zealand. The maximum records were twenty-one auroras in 1871 and sixteen in 1870. The other records vary from one to three in each year, except in 1882, when two displays—one in April and the other in November—each lasted over four days; but in this case some other cause may have been at work. During the same period of observations, as far as available, the relative area of sun-spots according to the best authorities has been, — Year. Area. 1868 8 1869 36 1870 78 1871 113 1872 99 1873 67 Year. Area. 1874 43 1875 18 1876 11 1877 11 1878 3 1879 7 The year 1884 was a marked maximum for the number of spots, and so also was 1894. The probable recurrent sun-spot maximum period is considered to be twenty-two years, which seems to be borne out by general experience, so that this last interval of only ten years appears to be exceptional. Mr. McLeod said we were greatly indebted to Sir James Hector for his valuable and interesting remarks, and especially for his explanation of Hertz's experiments, and the conclusions he (Sir James Hector) had drawn from them in connection with auroras. The telegraph system was

greatly disturbed during the last aurora, and on one occasion the instruments worked without the batteries while an aurora was taking place. Mr. Maskell said one practical point not referred to is whether the climate is affected by these disturbances. In Canterbury, in 1870 and 1882, after auroras, the summers were much wetter than usual. In 1867–68–69 the summers were so dry that the crops were ruined, and we had no auroras. In fact, wet weather generally follows auroras. It is possible that the electrical disturbances may have an effect on the climate, and it would be worth while to take notice of this. Sir Walter Buller said that in 1857 he saw an aurora in the Wairarapa. It was of a most brilliant crimson colour. He sent a description of it to the Independent, and would look it up. Mr. Hulke said that in the Northern Hemisphere it is sometimes so red as to resemble fire. Now that we have telegraphic communication we can connect the appearance of sun-spots with auroras. He described how, with a simple telescope, sun-spots could easily be observed. Mr. Hudson, in reply, said he was glad his short notes had been the means of getting so much interesting information from Sir James Hector. Sir James Hector, in reply, said that sun-spots had been associated with the growing of wheat, so that if auroras are affected by sun-spots they must also affect the climate. He had also observed an aurora in the Rocky Mountains in America in 1857. He thought it was better to give any information he possessed on the same night as Mr. Hudson read his notes, so that all the facts should be together. 2. Ornithological Notes, by Sir W. L. Buller: (1.) On Phalacrocorax colensoi, of the Auckland Islands, and P. onslowi, of the Chatham Islands. (2.) Œstrelata neglecta. -(Transactions, pp. 129, 132.) Exhibits: