91 , 
SURTEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY I, I88G. 
Station. 
Date. 
Stornoway . 
(Ard Point) 
1 Sept., 1884 
Loch Aylort 
Sept., 1884 
Kerrera . 
Aug., 1884 
Glasgow 
Aug., 1884 
Stranraer . 
Sept., 1884 
Stony hurst. 
1884 
Reading 
April 30, 1886 
Kew .... 
1884 
Greenwich . 
1884 
From Table 
IV. we see 
Declination. 
24 20-6 
23 
22 
21 
21 
19 
18 
18 
40-2 
25-4 
21-3 
46-2 
52-8 
I3T 
33-9 
18 7-6 
Date. 
Ang., 
Aug., 
Aug., 
Aug., 
Au£ 
1885 
1888 
1888 
1885 
1885 
1888 
^.ug., 
1887 
May 80, 1888 
1888 
1888 
Declination. 
Interval 
ill years. 
Secular rate 
of change. 
O 
24 
12-4 
0-9G 
- 8-5 
23 
49-9 
4 
- 7-7 
22 
41-8 
4 
• - 14-6 
22 
15-2 
1 
- 10-2 
21 
18-2 
1 
- 3T 
21 
13T 
4 
- 8-2 
19 
35'2 
3 
- 5-9 
17 
53-9 
2 
- 9-6 
18 
9-3 
4 
- GT 
17 40-0* 
(approx.) 
- G-9 
1837-86, 1857-86, and 1872-86 are nearly the same, the differences between them 
and the mean rate during; the period of our survey (6'‘9) being 0'‘4, O'Y, and 0'’4 
respectively. Assuming that if we subtract these numbers from the rates calculated 
for the same epochs for the other English stations in Table IV, we obtain the present 
rates at the stations, we find as a mean rate 7''0, which agrees closely with that of 
Greenwich. 
On the whole we decided to take a secular rate of — 7'’0 in England south of a line 
joining Eedcar and Barrow, and also in Wales, and in Ireland south of a line joining 
Dublin and Donegal. 
For the remainder of England and Ireland we have assumed the rate to be — 8'’0 
per annum. At the time when most of the Scotch observations were reduced we had 
not M. Moureaux’s results before us, and we hardly felt justified in departing from 
the rates given by the comparison of our observations with Mr. Welsh’s, on the 
evidence of the small number of stations at which the Declination was determined in 
1872. We, therefore, employed rates varying from — lO'A in the north of Scotland 
to — 8''8 in the south, the change on the east coast being somewhat greater than on 
the west. These may be a little too large but the error certainly does not exceed 
the variation which occurs between neighbouring stations. For the later Scotch 
observations we used a rate of — 9''0, 
The data for the determination of the secular change of the Horizontal Force are 
more scanty than in the case of the other elements. 
At the time of the 1837 survey the measures were comparative only, and though 
Sir E. Sabine afterwards reduced them to absolute values by means of the known 
absolute value and secular rate at Kew, we do not think any useful end would be 
attained by discussing them. 
M. Moureaux found that for the interval 1848-85, the secular variation in France 
attains its maximum + 0 •0027 (M.U.) at Bordeaux and decreases slowly towards the 
* From information kindly supplied by the Astronomer-Royal. 
N 2 
