
NATURE 

THURSDAY, OCTOBER 5, 1871 


OBSERVATIONS UPON MAGNETIC STORMS 
IN HIGHER LATITUDES 
*7"HE extension of the telegraph into the more northern 
latitude of the Shetland Islands, between 59° 51’ and 
60° 51’ 30” N., has afforded a much better opportunity of 
observing the frequency and variation of the magnetic 
and auroral storms that have of late excited some atten- 
tion and discussion in these pages. 
Some of the earliest recorded observations upon the 
strength and direction of these atmospheric storms, date 
from the time when the extension of the telegraphic wires 
over England rendered the phenomenon visible by the 
disturbance of the magnetic needle placed in circuit with 
the wires, and to a certain extent rendered possible the 
mapping down of the position and direction of the mag- 
netic storm over certain tracts of Great Britain. 
On the 24th September, 1847, remarkable magnetic 
disturbances were observed in London, and the direction 
and deflection of the magnetic needle noted. The effects 
of this magnetic storm were carefully observed at Daw- 
lish, Norwich, Derby, Birmingham, Rugby, Cambridge, 
Tonbridge, Wakefield, Edinburgh, and York. The mag- 
netic disturbance appears to have commenced about 
1" 5™ P.M. on the 24th, and continued with variable in- 
tensity until 7" 30™ A.M. on the 25th. 
It may be interesting to give some of the galvanometer 
readings recorded as indicating the rapid oscillation and 
deflection of the galvanometer needle. In the period of 
time between 4" 17™ P.M., and 5" 48" P.M. on the 24th, or 
in about one hour and a half, the direction of the cur- 
rent had changed no less than ten times, showing a 
maximum swing of the needle over an arc of 50°. 
H, M. deg. HM. deg. 
4.17 15 left 5.5 15 left 
4.20 20 right Baio Nee ep 
4.25 1 5.16 to right 
4.25.30° TO! 55 5.22 18 left 
4.35 () ay 5.25 14 right 
4.38 W235 5.28 13 left 
4.45 20 55 5-32 20 55 
4.50 To left 5-34 AD cp 
4.51 17 5 5.42 29 » 
455 oy 5.48 3° 
4.56 8 right 
During this magnetic storm, the variation of the dipping 
needle which was observed in London every 30", ranged 
between 69° 30’ and 67° 50’. 
In some cases these magnetic storms were so severe as 
to impede the working of the railway signals. On the 
18th of October, 1841, a very intense magnetic disturbance 
was recorded, and amongst other curious facts mentioned 
is that of the detention of the 10.5 P.M. express train at 
Exeter sixteen minutes, as from the magnetic disturbance 
affecting the needles so powerfully, it was impossible to 
ascertain if the line was clear at Starcross. The superin- 
tendent at Exeter reported the next morning that some 
one was playing tricks with the instruments, and would 
not let them work. 
VOL, Iv. 

441 


It will be fresh in the memory of many of our readers 
that during the month of October last year, very remark- 
able and brilliant “auroras” were observed in London, 
chiefly of a deep blood-red colour, spreading from the 
zenith over a great portion of the heavens, 
It is, however, in the more northern latitude of the 
Orkney and Shetland Islands that the grandeur of these 
wonderful electrical phenomena can be observed, and that 
reliable data can be obtained from which hereafter some 
practical result may be deduced. 
As observed in Orkney and Shetland, the aurora, as a 
general rule, appears to concentrate and emerge from 
behind a dense mass of dark cloud lying low down in the 
horizon towards the north. The edge of this cloud-bank 
is serrated and jagged, as if the mass were electrically in 
a high state of tension, From behind this cloud-bank 
“dark” streamers will appear to start up high into the 
zenith, appearing as if attenuated portions of the edge of 
the cloud-bank had been dragged by some invisible power, 
these dark auroral rays being at the same time transparent 
as regards the power of transmitting the light of the stars, 
which shone through with undiminished splendour. At 
the same moment that these dark rays are emicant, 
brilliant green, violet, crimson, and white rays appear to 
stream upwards towards the zenith, but always with a less 
persistence of duration. These coloured scintillations 
change with greater rapidity than the black rays. 
During the month of December of last year, some very 
vivid prismatic tints were observed from the Island of 
Eday. From careful observation it was then remarked 
that the red coloured rays appeared generally to be of a 
partially opaque nature, and it could be readily seen that 
the light of a star, waen viewed through the red scintilla- 
tion, was dimmed as compared with the brilliancy of the 
same star when observed through the scintillations of 
another colour. 
In some of these displays, the most vivid and varied 
colouring was exhibited. These were noted down as 
visible to the eye at the same time, and as the colours 
were observed in contrast, the distinctiveness and 
brilliancy of the tint became the more decided. Black, 
pale yellow, strong yellow, white, violet, pale blue 
bright green, crimson shade fading into a reddish pink, 
pale orange, and a delicate sea-green tint. So far no- 
thing approaching to the indigo hue has been noticed. 
With this exception, the entire prismatic colours and 
| blending tints may be said to have been perfectly deve- 
loped in the rapid electrical scintillations of the aurora. 
The colours fade away and change with astonishing 
rapidity, and this variation in tint will take place without 
apparently any great electrical disturbance in the special 
ray observed, beyond a slight flickering motion. In these 
regions, where the atmosphere is so perfectly still and at 
times calm, repeated observation has determined the exist- 
ence of very appreciable sound to the ear, as an accom- 
panying phenomenon [to the rapid rush of the auroral 
streams towards the zenith. The intensity of the sound 
emitted variesconsiderably. At times, it greatly resembles 
that of the rushing noise caused by the firing of a rocket 
into the air when reaching the ear from a distance. At 
other times it has a strong resemblance to the sound pro- 
duced by the crackling of burning embers, but wanting in 
any very distinctive sharpness. 
AA 
