34 
THE KEY. STEPHEN J. PERKY ON THE MAGNETIC 
The observations will, for clearness’ sake, be arranged under the successive heads of 
Dip, Intensity, and Declination. 
The Magnetic JDij). 
The method of observing differed in nothing from that usually employed. The mag- 
netic prime vertical was first found by four readings of the needle when vertical, and the 
circle then set so that the needle might oscillate in the magnetic meridian. Each end 
of the needle was read with the face of the circle first East and then West ; next, 
the axis of the needle was changed on the agate planes, and the same observations again 
taken ; and lastly, the whole was repeated after reversing the poles of the needle. Each 
pair of readings was repeated after lifting the axis of the needle on its Ys, and if a dif- 
ference of 2' was found, fresh sets were observed. 
The results are contained in the following Table (I.). 
Number of 
readings. 
Dip. 
1 . 
2. 
3. 
No. 1. 
No. 2. 
No. 3. 
O / 
O / 
36 
34 
65 50-2 
65 55 2 
32 
32 
65 50 3 
65 49-9 
32 
65 48 3 
36 
34 
36 
66 29-5 
66 23 9 
66 30 T 
34 
44 
44 
65 51-4 
65 45-3 
65 39-5 
34 
44 
65 120 
65 87 
32 
65 8*5 
34 
34 
64 33-9 
64 26 5 
42 
34 
64 32-9 
64 26 3 
34 
32 
34 
63 25-6 
63 22-0 
63 22-6 
32 
63 26-6 
44 
62 30 9 
34: 
36 
62 32 7 
62 23-3 
32 
30 
62 30-2 
62 32-5 
44 
31 
62 3-5 
61 534 
40 
62 1-4 
34 
62 4 1 
40 
38 
62 1-2 
62 1-2 
36 
40 
63 27 8 
63 22 1 
32 
42 
64 34-6 
64 327 
40 
34 
36 
65 55 - 3 
65 56-9 
65 57 0 
44 
65 50 1 
38 
... 
16 
66 41 - 3 
66 36-5 
Station. 
Date. 
G.M.T. 
h 
m 
11 
26 
1 
9 
43 
} 
5 
45 
P.M. 1 
10 
28 
A.M. f 
5 
44 
P.M. 
11 
9 
] 
0 
4 
l 
3 
41 
P.M, ) 
2 
59 
P.M. | 
3 
24 
P.M. 1 
10 
49 
A.M. J 
6 
9 
p.m. i 
4 
9 
P.M. f 
7 
51 
A.M. 
Mean. 
Place of observation. 
Paris 
Laval 
Brest 
Vannes 
Angers 
Poitiers 
Bordeaux 
Abbadia . . 
Bayonne. 
Pau 
Toulouse 
Perigueux 
Bourges ... 
Paris 
1868. 
Aug. 12 
„ 1-1 
„ 15 
„ 18 
22 
„ 24 
„ 25 
„ 26 
„ 27 
„ 29 
,, 30 
1 
Sept. 
} 
{“« } 
{.Si } 
Amiens 
r 
5 30 p.m. 
1 
1 
4 20 
J 
/ 
5 28 p.m. 
1 
1 
3 25 
1 
6 10 p.m. 
f 
9 13 A.M. 
1 
1 
10 40 
J 
/ 
11 23 
1 
i 
5 28 
J 
/ 
11 3 
i 
1 
2 58 
j 
9 28 
I 
10 38 
L 
1 
11 43 
1 
9 3 
f 10 35 
1 
1 
4 38 
1 
65 52-7 
j 65 49-5 
66 27-8 
65 48-4 
65 97 
| 64 29-4 
| 63 
}62 
62 
} 61 
} 
63 
64 
24- 2 
290 
3L4 
59-4 
2-2 
25- 0 
33 7 
65 54 8 
66 41-3 
Garden of Coll. Vaugirard. 
Maison St. Michel. 
3 Rue d’Aiguillon. 
Garden of College. 
8 Rue du Faubourg St. Michel. 
Meadow of the College. 
Grounds of College. 
Magnetic Observatory. 
Lamont’s Station. 
Grounds of College. 
Garden of the Grand Seminaire. 
Rue neuve St. Laurent. 
Garden of Coll. Vaugirard. 
Garden of St. Acheul. 
In the above Table the G.M.T. is arranged in the same order as the observations. 
The exact site of each separate observation has been carefully noted, but the details 
