102 ME. C. V. WALKEE ON MAGNETIC STOEMS AND EAETH-CTJEEENTS. 
trodes that would’ continue active, and highly active too, not for minutes merely, but 
often for quarter and half hours. We have no approach to such polarization in the ordi- 
nary use of the telegraph. Besides, it could with equal propriety be attributed to the 
S. currents as to the N. ; for all our experience thus far leads to the conclusion that no 
one thing can be said of the one class of current that cannot with equal truth and equal 
force be said of the other. 
Had results such as those before us been made more public heretofore, the learned 
Professor of Geneva could not but have modified his views ; for with the proved exist- 
ence of so large a quantity of S. current, he could scarcely have presented the auroral 
theory in its present form, because the N. currents entering at the polar regions and 
flowing southward is the essential feature of his theory. 
While investigating the value and duration of earth-currents, our attention has hereto- 
fore been almost confined to a solitary telegraph group, namely, to the Margate — Ashford 
line ; and the currents of positive electricity found moving from Margate, the more north- 
erly station, to Ashford, have in a general: w^iy been termed N. currents, and vice versa. It 
is obvious, however, that the electric flood, 'in its course through the mass of the earth, 
might vary greatly in azimuth and still give the. same apparent result. Pig. 2, Plate III. 
will explain this. If the line marked 13 represents the bearing of the Margate — Ashford 
group in respect to the magnetic meridian N.S., Margate being at the circumference of 
the circle, an earth-current from any azimuth, not .exceeding 90° to the north or south, 
right or left of the line 13, would enter the telegraph wire at Margate and leave it at 
Ashford. The shaded portion of the circle shows this limit in either direction. The 
azimuth of the line in question is 72° E. of N. ; so that the limit in one dhection is 18° 
W. of N., and in the other 18° E. of S. ; and therefore what we have in general terms 
called a N. current, might be the result of an actual S.S.E, current, just as it might 
equally be of a N.N.W. current. The real direction of the currents in the earth cannot 
be determined from observations made on a single telegraph group ; neither can it be 
determined by simultaneous observations made on different telegraph groups, unless there 
be some among the groups that have widely different azimuths. 
The Map (Plate II.) that accompanies this communication shows the district of 
England over which these observations extend. I have omitted all intermediate sta- 
tions, and have inserted, with here and there an exception, only the name of the tele- 
graph stations that are concerned in this investigation. The magnetic meridian makes 
an apgle of 21|-° W. with a vertical passing through the Map. ' It is necessary to bear 
this in mind when referring from Tables XI. and XII. to the Map.^ The fine lines di’awn 
on the Map represent the railway routes, and at the same time the routes along which 
the telegraph whes are led. Direct lines drawn from station to station are used with the 
magnetic meridian in obtaining the bearings given in Table XI., and the values shoum 
in the first column of distances in the same Table. 
I have selected eighteen pairs of telegraph terminal stations, each one differing from the 
other in azimuth, and have referred them to the magnetic in preference to the astrono- 
