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X. On Magnetic Calms and Earth-Currents. 
By Chaeles V. Walkee, Esg., F.B.A.S. 
Eeceived February 3, — Eead Eebruary 13, 1862. 
I USE the word “ calm ” in a purely negative sense' — not storm. For many months the 
earth has shown few marked signs of activity. Very few notable earth-currents have 
attracted attention since those of 1861, January 22 to 26, referred to in the last para- 
graph but one of my paper “ On Magnetic Storms, &c.,” read February 14*. 
I had not proceeded far in the discussion of the results which form the subject of 
that communication, without discovering that I possessed close at hand, and under my 
immediate control, the means of verifying the conclusions to which I had arrived as to 
the general direction of earth-cmu’ents ; of extending the observations to periods when 
the earth is free of signs fi’om extraordinary activity; and of further pursuing my 
mquiries. 
In sections 3 and 4 of Table Xll.f I grouped together a series of observations ; and 
in fig. 5 of Plate III. gave a graphic illustration of the same ; and from those data 
deduced the approximate Direction of Earth-Currents ; and determined the azimuth of 
the drift to be in turn about N.E. and S.W. 
I was unable to include many cases in these sections of the Table. Simultaneous 
observ'ations including both limiting lines were few; I was therefore glad to have so 
ready at hand the means of multiplying and modifying them. The groups of observa- 
tions in the Table referred to were made on eight or nine difierent lines of telegraph, 
making various angles with the magnetic meridian ; and were bounded on the one hand 
by the London-Tonbridge line, making an angle Avith the magnetic meridian of 13°W., 
and on the other hand by the Dover-London line, making an angle of 136° E., the 
two lines making with each other an angle of 149°; from which it could be deduced, 
and was shown, that the direction in which the currents moved was included within an 
arc of (180°— 149°=)31°; and that this arc Avas situated midway between the lines in 
question (which are those set off on fig. 5, Plate III., and numbered there, as well as in 
Tables XI. and XII., 23 and 26 respectively), extending from 46° to 77° E. of magnetic 
north, or W. of magnetic south. 
The Dover-London telegraph Avnes pass Tonbridge, where they enter my private 
ofiice, being attached to a telegraph instrument placed there. This gives me the imme- 
diate command of the Dover-London line, numbered 26 — 25 in Table XI. p. 130, and 
in figs. 1 and 5, Plate III., and which is one of the limiting or boundary lines. By 
cutting off the communication Avith Dover, that is to say, by connecting the wire with 
* Philosopliical Transactions, 1861, p. 113. f Ibid. 1861, p. 131. 
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