August 19, 1S80] 



NATURE 



361 



quartz, mil be able to make measurements of any required degree 

 of accuracy. !'• G. Tait 



The Club House, St. Andrews, N.B., August 12 



Dimorphism of "[Nature "Jon June 17 

 With 'reference to the statement in an editorial note in 

 Nature, vol. xxii. p. 317, that one statement of mine "does 

 not accord well " with another, I must request to be allowed to 

 show that this observation is incorrect. 



I was told by a friend on July 27 (five weeks after the event) that 

 there had been apparently two issues of Nature of June 17, and 

 that Prof. AUman was intending to wiite to Nature quoting the 

 uncorrected issue (which was unfortunately the one which had 

 been supplied to him) in support of his statement, in Nature, 

 vol. xxii. p. 218, which I had declared to be a misconception 

 (Nature, vol. xxii. p. 241), viz., that I differed from him as to 

 the existence of a marginal canal in the new medusa. Accord- 

 ingly I wrote on July 28 to the editor, requesting him to state, 

 "if necessaiy," that there had been two issues, and expecting 

 that this explanation would be inserted immediately after Prof. 

 AUman's letter, published in N.'^ture, vol. xxii. p. 290. The 

 explanation was not, however, given, and it was left to me to 

 write my letter of two days later date (July 30), which was pub- 

 lished in Nature, vol. xxii. p. 316. I had in that two days 

 interval " ascertained " by further evidence that there were 

 actually two issues of No. 555 of Nature, and my "great 

 surprise" was due to the fact that the editor of Nature should 

 have allowed Prof. AUman's letter to appear without offering 

 any explanation of the direct opposition between his quotation 

 and mine — the cause of which was well known at the printing 

 office of Nature. 



It is thus clear that my letter of July 30 is consistent with my 

 letter of July 28. E. Ray Lankester 



[We willingly give space to the above letter, and accepting 

 the interpretation of the former one which Prof. Lankester now 

 gives us, we regret having made the observation to which Prof. 

 Lankester alludes. We may further add that the insertion of 

 the reference to the letter in question was due to an oversight. — 

 Ed.] 



Magnetic and Earth-Current Disturbance 



It may be of interest to point out that a magnetic disturbance 

 has just been experienced at the Royal Ob:ervatory greater in 

 magnitude than any that has occurred for some years. 



On August II, at 10.30 a.m., active disturbance suddenly 

 commenced, and continued until midnight, accompanied, as usual, 

 by the exhibition of earth currents. The magnets were then 

 generally quiet until about noon of August 12, when disturb- 

 ances of ttill greater magnitude began to be shown, continuing 

 till 6 a.m. of August 13. During the latter period the variations 

 in the magnetic declination and horizontal force were frequent 

 and large, especially between neon and 4 p.m., and between 7 

 and 9 p.m. Between noon and 4 p.m. there was also a con- 

 siderable increase of vertical magnetic force. During the whole 

 period, from noon of August 12 to 6 a.m. of August 13, earth- 

 currents were continuous and strong, and especially strong at 

 those times at which the magnets were most disturbed. 



It seems well at the present time to warn telegraph engineers, 

 and especially those concerned in the laying of submarine cables, 

 that disturbances of the character of that described above may now 

 become not unfrequent as compared w ith the quietness of recent 

 years. I may perhaps be permitted here to refer to a short 

 paper, "Note on Earth-Currents," to be found at p. 214 of vol. 

 viii. of the Journal of the Society of Telegraph Engineers, as 

 containing information on the question of magnetic disturbances 

 and earth-currents, probably not without interest at this time. 



William Ellis 



Royal Observatory, Greenwich, August 14 



P.S. — During the evening and night of August 13-14 large 

 magnetic disturbances again occurred, accompanied as before by 

 strong earth-currents. 



Aurora Borealis and Magnetic Storms 

 The epoch of grand auroras and magnetic storms has again 

 returned, as %\as evident from the fine displays seen here on the 

 evenings of the nth and 12th, and these are as usual accom- 



panied by an increase in the number and size of the sun-spots, 

 and in the development of the solar prominences. The aurora 

 on the nth was grand, but that which followed it on the I2lh 

 recalled vividly the magnificent displays of 1869, 70, and 71. 



On the 1 2th my attention was first called to the phenomenon 

 at loh. 25™. p.m., when the northern horizon was skirted by a 

 bright white haze terminating in an ill-defined arch, from which 

 sprang a large number of broad streamers stretching towards the 

 zenith. The bank of white light on the horizon extended from 

 about 15' E. of N. to 45° W. of N.,and some of the streamers 

 attained an altitude of fully 60" or 70°. The brilliancy of the 

 individual streamers was varying rapidly, but there was little 

 variety in the character of the phenomenon. 



At loh. 30m. the brightest streamer was 3° W. of N. Ten 

 minutes later this brilliant white band of light had moved 

 gradually westward, and was some 25" W. of N., when it faded 

 away. Some streamers were still more W. of N., and others 

 again were slightly E. of N. 



At loh. 46m. there was nothing remaining of the aurora 

 except a cloudy whiteness in the north, the rest of the heavens 

 being a deep blue. A minute later streamers were again 

 appearing. 



At loh. 56m. a very bright streamer formed 2° E. of N., and 

 then a similar band of light appeared 5° W. of N., followed in 

 rapid succession by other streamers 10°, 20°, and 45° W. of N., 

 each streamer fading away before the succeeding one became 

 very bright. 



At iih. cm. a single narrow band of intense white light 

 stretched from the horizon towards the zenith, passing through 

 Cor Caroli. 



At I ih. 7m. the light in the N. and N.N.W. again brightened 

 up, but there was no further appearance of streamers. 



The magnetic storm that accompanied the aurora of the 12th 

 was one of the most violent ever recorded at this observatory, 

 and was very similar in character to the magnificent storm 

 of 1869. 



On the evening of the nth the magnetic needle was very 

 irregular in its movements, but it was only towards midday of 

 the I2th that the storm really began. The oscillations from the 

 beginning were very rapid and extensive. The first great move- 

 ment began at nh. 34m. a.m., and between I2h. iSm. and 

 I2h. 24m. the declination magnet moved 1° 6' 45" eastward. It 

 then returned westward, and at ih. 4m. the reading had increased 

 by 1° iS' 13". Between 7h. gm. and 7h. 29m. p.m. the needle 

 moved 59' 1 8" eastward, when it attained its minimum ; it then 

 returned quickly towards the west, and after a double sweep it 

 reached its maximum at Sh. 13m., the change of declination in 

 46m. being \° 27' 23". 



The oscillations of the V. F. magnet were as great as those of 

 the declination. The chief maximum occurred at 3h, 40m. p.m., 

 and there were three decided minima at about 10 p.m. midnight 

 and 2 a.m., the two latter of which were lost from the oscillation 

 being too great to be recorded on the photographic cylinder, and 

 the first show ing a change of I '9 inch of ordinate in 5m. 



The variation of the H.F. magnet was very large, but not so 

 remarkable as that of the V.F. 



On the 13th the magnetic storm continued greatly to disturb 

 all the magnets, but it was less violent than on the preceding day. 



Stonyhurst Observatory, August 15 S. J. Perry 



There was a beautiful display of the aurora here last night. 

 Between ten and eleven o'clock the streaks extended from the 

 horizon to the zenith. The colour was principally pale blue, but 

 a reddi^h tinge was occasionally discernible. I obseiwed what I 

 thought was a lateral movement of some of the sti'eaks. A bright 

 spot suddenly made its appearance to the westward of a small 

 black cloud, seemed to move slowly eastward and disappear. 

 There was a slight breeze from the east at the time, but I do not 

 think tliat the clouds were moving sufficiently rapidly to account 

 entirely for the phenomenon. J. A. B. OLIVER 



Springburn, Glasgow, August 13 



A FINE display of aurora was visible here on the night of 

 Thursday, Augu-t 12, about 10.30. White streamers, stretching 

 vertically from the horizon nearly to the zenith, occupied the north- 

 west segment of the heavens from the pole to Arcturus. There was 

 a narrow bank of cloud along the horizon, and I thought at first 

 that the streamers might be shadow-phenomena from the sun ; 

 but the hour was too late, and the rapid variations of form and 



