OF AUGUST 28 TO SEPTEMBEE 7, 1859. 
429 
nature of that relationship which manifestly exists between auroral displays, earth- 
cuiTents, and magnetic disturbances. 
I cannot think that the latter are caused directly and mainly by the two former, but 
rather that the three are simultaneous effects produced by the same cause. I believe 
that this is the opinion entertained by General Sabuste, who has investigated the subject 
from another point of \iew. 
A very remarkable feature of this disturbance was its period of about six hours, which 
is most distinctly shown in the curves of the horizontal and vertical forces. For about 
three hours the two components of the earth’s force at Kew were diminishing, and for 
the next three hours these were increasing, until, after the lapse of about six hours, they 
had again attained their normal values. Were this due to the direct action of an elec- 
trie current, it would require that this current should have flowed in the same direction 
for six hours; or at least that it should have been so limited in direction as to influence 
the earth’s magnetism at Kew in the same manner for about six hours. 
Eeferring now to the accounts collected by Professor Loomis of the influence of this 
gi’eat storm upon telegraphic wires, and also to a paper on magnetic storms and earth- 
currents, communicated by Mr. C. V. Walkee to the Eoyal Society on January 31, 1861, 
we find that the duration of the currents produced in the telegraphic wires is for the 
most part exceedingly small. The 1-minute currents (says this last author) are most in 
number; then, in order, the 2-minute, 3-minute, 4-minute, -^-minute, and 5-minute. 
Now it seems impossible that any combination of such currents of short period and 
rapid reversal can account for the six hours’ march of the earth’s force at Kew, and 
equally impossible not to associate these currents of small period with the rapid and 
minute changes wliich give a pulsatory character to the disturbing force, and a serrated 
appearance to the curves. 
It is not difficult to conceive a mode of action of the primary force which would pro- 
duce these effects. 
IVe have grounds for supposing this primary disturbing force to reside in our 
luminary. 
The earth may be \iewed as the iron core of a Euhmkoeff’s machine, separated by an 
insulating medium (that is to say, the lower strata of the atmosphere) from a conducting 
medium (that is to say, the upper and rarer strata of the atmosphere). 
Suppose the primary current in the sun suddenly to become increased or diminished 
a little. This will not produce a reversal in the magnetic state which this current has 
communicated to the earth, but merely a small change in its amount ; or, in other words, 
the magnetic disturbance produced by the current will merely be somewhat increased or 
diminished. 
The change in the primaiy current, heightened by the change of the iron core, will, 
on the other hand, produce a secondary current : 
1st. Along the surface of the earth, which is sufficiently conducting for the purpose ; 
2nd. Along the upper strata of the atmosphere ; 
