90 
MR. A. W RUCKER AND DR. T. E. THORPE ON A MAGNETIC 
Station. 
Declination. 
Secular rate of change. 
Jan. 
1, 1869. 
Jan. 1, 1885, 
1869-8.5. 
1859-85. 
Amiens .... 
O 
18 
19-0 
O 
16 
34-7 
- 6-5 
- 7-4 
Boi'deaiix .... 
18 
12-5 
16 
45-7 
- 5-4 
- 7-0 
Clermont .... 
16 
27-6 
15 
25-0 
- 3-9 
- 6-9 ! 
Dijon. 
16 
36-7 
14 
45-2 
- 7-0 
- 7-2 
Grenoble .... 
15 
49-3 
14 
11-0 
- 6T 
- 6-8 
Mai'seilles .... 
15 
41-5 
14 
0-0 
- 6-3 
- 6-7 i 
Monaco .... 
14 
31-4 
13 
10-5 
- 5 0 
— 6'5 ’ 
Monlins .... 
16 
29-2 
15 
25-6 
- 4-0 
— 69 
Paris. 
17 
50-5 
16 
10-2 
- 6 3 
— 7'4 1 
Perignetix .... 
17 
40-9 
16 
8-6 
- 5-8 
- 7-0 i 
Poitiers. 
18 
18-4 
16 
40'8 
- 6-1 
- 7T 
Toulouse .... 
17 
7-3 
15 
41 4 
— 5'4 
- 6-8 
iMean 
— 5-6 
- 7-0 
This result—that the rate of decrease is diminishing—is in accord with the conclu¬ 
sions drawn by M. Moureaux himself from a comparison of his own observations 
with those on which a magnetic map of France for the epoch 1875 was based by 
M. Marie-Davy (Joe. cit., p. 166 ). He did not, however, make use of this fact, as 
the number of observations employed by Marie-Davy was small, and they were 
taken at stations irregularly distributed over France. He does not cite the observa¬ 
tions of Father Perry, which, as the above Table shows, strongly support the same 
view. 
In the next Table we give such observations as were made at English observatories 
or by ourselves during the progress of the survey which bear on the question under 
discussion. No verv definite conclusions can be drawn from them. 
o’ ^ 
Two single observations at the interval of a year, as at Kerrera and Glasgow, are 
hardly sufficient for the purpose of deducing a secular rate. Loch Aylort and 
Stornoway are both disturbed stations and the results are thus less trustworthy. Tire 
general evidence that the secular change is greater in higher latitudes is opposed by 
the fact that Stonyhurst gives a less vahie than Kew and Greenwich. If the increase 
with latitude which obtains in France were maintained in England, the value at Paris 
being taken at — 6''3, we could deduce —6'’8 for London ; — 7'‘7 for Edinburgh; 
and — 8'’2 for Wick ; of which the two latter are less than the values for the epoch 
1872-86 given in Table IV., p. 88. 
