ME. C. V. WALKEE ON MAONETIC STOEMS AND EAETH-CEEEENTS. 103 
mical meridian, in order the more readily hereafter to compare the determined direction 
of earth-currents with the beha’sdour of the declination-needle during their existence. 
The mean westerly magnetic declinations at Greenwich have been — 
For 1857 .... 21 34 30 
For 1868 . . . . 21 29 30 
For 1859 .... 21 23 30 
I have therefore taken 215 -° as an approximate value for 1860 sufficiently near for the 
present purpose*. Whitstable and Canterbury are as nearly as may be on this meridian, 
the former being to the north of the latter. Table XI. contains these eighteen groups 
arranged in order, and in three divisions: 1 st, those on the magnetic meridian; 2 nd, 
those bearing East of it; 3rd, those bearing West of it. The numbers in the left-hand 
column apply to the stations in order ; and in using them for reference, 1 — 2 , or more 
briefly 1, means yi'om Eed Hill to Brighton; 2 — 1, or more briefly 2, from 
Brighton to Bed Hill ; and so of the rest. The odd numbers are all made to fall to the 
north of a hne drawn at right angles to the magnetic meridian ; and the even numbers 
to the south of the same line. The figures in the column headed “Bearings” are 
approximate, fractions of degrees being neglected. They extend from the 82nd degree 
West of North to the 80th degree East, embracing in all 162°, or only 18° short of the 
half of a great cfrcle, — giving, therefore, a very wide field for observation. The Table 
also contains the distances measured in dii’ect line from point to point, and also the 
distances along the route pui’sued by the telegraph wire which connects each two points 
respectively. 
Fig. 1, Plate HI. is a graphic representation of Table XI. The numbers 1 — 2, 3 — 4, 
&c. correspond with those in the Table; and the lines are laid down at the angles 
gathered from the Map and given in the Table. 
From time to time I have secured simultaneous observations from more groups than 
one, frequently from several groups. It is not necessary to encumber this communica- 
tion with specimens of all combinations. I have selected four, beginning at fig. 2 
(already refen’ed to, and which is the most simple but least instructive case), and con- 
cluding with fig. 5 (which is the most full and conclusive). 
Fig. 2 represents the most common of all cases, a current collected by the Margate — 
Ashford wire No. 13. In this wh’e, as well as in its near neighbour No. 15, the Eams- 
gate — Ashford wfre, a current may always be found, if detected elsewhere. The effects 
are similar and simultaneous on all the instruments of this circuitous telegraph group, 
namely, at Margate, Kamsgate, Deal, and Ashford. 
Fig. 3 represents a case almost equally common. No. 13, as before, is the Margate — 
Ashford group, and No. 17 the Margate — Eamsgate. By setting-off 90° from each line 
in the direction of the other line, we define the limits within which an earth-current 
* Mr. Aiex’s Eeport, published since this paper was read, gives it 21° 14' 20". — C. V. W. 
