20 
THE KEY. STEPHEN J. PERRY ON THE MAGNETIC 
The rate appears to have been slowly diminishing from July to October, and to have 
suffered very little disturbance from the travelling. I was unable during the journey to 
make more frequent comparisons ; but altitudes of the sun were taken as before at each 
station by way of check, though they were fortunately found to be unnecessary. 
The observations for finding the sun’s azimuth are much less trustworthy than in the 
preceding year, owing to a change of instrument. The transit-altazimuth of Cooke, 
which worked so steadily in 1868, was replaced, on account of its heaviness, by a Jones 
theodolite, which, though much more portable, had the great disadvantage of being far 
less steady, and thus interfering very considerably with the accuracy of the results. 
In all the observations taken during this survey with the declination needle, the scale 
of the collimator magnet was inverted twice at each station, so as to render unnecessary 
any other determination of the zero of the scale, which might accidentally be slightly 
altered whilst travelling. 
In the following Table the first readings of the azimuth of the fixed mark were taken 
throughout on the theodolite circle, and the second readings on the circle of the unifilar. 
Table XV. 
Station. 
Date. 
Chronometer. 
Error at 
noon, G.M. T. 
Daily 
rate. 
Azimuth of Sun. 
Azimuth of 
mark. 
| Azimuth of 
magnet. 
h m s 
m s 
s 
Kheims 
Aug. 10 
9 14 3-1 a.m. 
+5 45-70 
+ 1-97 
169 52 45 
20 48 15 
178 3 5 
188 52 1 
Metz 
„ 12 
8 33 34-3 a.m. 
+5 49-64 
,, 
92 18 45 
139 10 15 
116 18 10 
119 37 59 
Strasburg 
„ 14 
2 35 26-0 r.M. 
+5 53-57 
,, 
165 39 45 
141 38 0 
178 48 0 
125 26 38 
Issenheim 
„ 17 
9 18 51-8 a.m. 
+5 59-48 
79 48 30 
54 24 0 
61 39 10 
93 48 21 
Dole 
„ 19 
9 40 3'3 a.m. 
+6 3-42 
,, 
156 32 15 
176 53 0 
154 6 55 
166 12 3 
Dijon 
„ 21 
9 44 21-2 a.m. 
+ 6 7-36 
,, 
25 13 0 
136 25 0 
173 41 45 
93 6 46 
Avignon 
„ 25 
8 30 0 0 a.m. 
+6 15-23 
,, 
99 21 45 
36 8 30 
193 36 30 
127 14 53 
Marseilles 
„ 27 
1 1 50 58 3 a.m. 
+6 19-16 
+ 1-98 
140 57 0 
132 25 15 
109 54 0 
100 51 l 
Monaco 
„ 29 
9 0 57 0 a.m. 
+6 23-10 
,, 
28 21 0 
150 17 15 
127 45 25 
227 54 27 
Montpellier 
„ 31 
8 35 28- 1 a.m. 
+6 27-04 
,, 
74 35 40 
92 30 25 
130 4 45 
161 12 24 
Grenoble 
Sept. 3 
9 54 428 a.m. 
+6 32-95 
„ 
8 16 45 
61 21 38 
158 37 7 
130 8 54 
N. D. de Myans... 
„ 4 
1 30 31-9 r.M. 
+ 6 34-92 
,, 
140 8 0 
158 17 15 
195 34 15 
122 18 5 
Mongre 
„ 7 
8 35 32 0 a.m. 
+ 6 40-83 
„ 
21 22 45 
70 55 30 
108 25 10 
103 45 39 
St. Etienne 
„ 8 
9 0 12'8 a.m. 
+ 6 42-80 
>> 
62 53 15 
170 13 15 
267 42 20 
197 51 13 
Clermont 
„ 10 
8 51 30-2 a.m. 
+ 6 46-74 
,, 
53 1 55 
109 31 30 
146 53 5 
131 45 25 
Moulins 
„ 12 
8 36 4-0 a.m. 
+6 50-68 
,, 
64 4 0 
110 50 45 
148 15 25 
145 2 26 
Paris 
„ 14 
9 10 35-8 a.m. 
+6 54-62 
,, 
171 30 15 
167 42 0 
265 9 40 
122 33 14 
Douay 
„ 17 
11 58 28-9 a.m. 
+ 7 0-56 
,, 
152 27 20 
159 14 45 
256 45 25 
228 56 0 
Boulogne 
„ 19 
3 45 24-7 p.m. 
+ 7 4-52 
„ 
177 12 25 
48 51 45 
266 19 10 
131 45 8 
