92 
MR. A. W. RUCKER AKD DR. T. E. THORPE OH A MAGHETIC 
east, being •0025 at Paris and + 0’0023 at Nice and Mezieres {loc. cit., p. 167). The 
mean value obtained by the Pev. S. J. Perry in 1869 by comparison with Lamont was 
0’0023 (‘ Phil. Trans./ Vol. 160, 1870, p. 48), which was increasing by about O'OOOOOS 
per annum and would correspond to 0'0025 at the present time. 
By comparison of our own observations with those of Welsh we obtain O’OOIS as a 
mean for Scotland between 1857 and 1886. 
The following Tables give these values and those which were obtained at the 
English observatories or by ourselves during our survey. 
Secular Change in Horizontal Force. 
1 
1 
1 Station. 
Welsh. 
R.and T. 
Difference. 
Interval. 
Secular rate 
of change. 
Uncorrected foi 
■ V and A. 
1 
Years. 
1 
Dumfries. 
1-6006 
1 6522 
-0.516 
27 
-0019 J 
Stranraer . 
1--58.53 
1-64.33 
-0580 
27 
■0021 
j Ayr. 
1-.5756 
1 6317 
-0561 
27f 
■0020 
\ Oban. 
1-5451 
1-6083 
-0632 
31 
■0020 
Fort Augustus .... 
1-51.34 
1-5643 
-0509 
28 
■0018 1 
Inveriipss. 
1-5093 
1-5653 
-0560 
28 
■0020 
Aberdeen. 
1-5166 
1-5735 
-0569 
071 
■0021 
Pitlochrie. 
1 -5341 
1-5926 
-e585 
■0021 
1 Dalwhinnie. 
1-.5377 
1-5926 
-0549 
•0020 
i Ediiiburgli. 
1-5665 
1-6162 
-0497 
27^ 
•0018 
1-5697 
-0465 
26f 
•0017 ' 
Kyle Akin. 
1-5009 
1-5407 
-0398 
, , 
•0015 ; 
f 1-4773') 
Stornoway. 
1-4783 V 1-4783 
1-5122 
-0339 
26 tV 
•0013 
[ 1-4794 j 
Callernisb. 
1-4731 
1-52.36 
-0505 
27 
•0019 
Loch Inver . 
1 -4499 
1 - 49.50 
-0457 
■0018 
Thurso. 
1-4763 
1-5209 
-0446 
26| 
■0017 
Lerwick. 
1-4313 
1-4718 
-0405 
27 
•0015 
11-4669') 
Kirkwall. 
<1 1 4725 U-4716 
1-5111 
-0395 
27 
•0015 
[I-4753J 
1 
Wick. 
I-47O6 
1-5117 
-0411 
26| 
•0015 
Golspie. 
1-4893 
1-5390 
-0497 
26| 
•0019 1 
Mean 
.. 
•0018 ' 
Station. 
Date. 
H. 
Date. 
H. 
Interval 
in years. 
Secular rate 
of change. 
Stornoway 
Aug. 19, 1885 
1-5200 
Aug. 14, 1888 
1 5220 
3 
+ -0007 
Loch Aylort . 
Sept. 12, 1884 
1-5577 
Aug. 2, 1888 
1-5774 
4 
4- -0049 
Stranraer 
Sept. 18, 1884 
1-6423 
Aug. 28, 1888 
1-6470 
4 
+ -0012 
Stonyhurst . 
1884 
1-6954 
1887 
l-7o24 
3 
+ -0023 
Kew .... 
1884 
1.8056 
1887 
1-8091 
3 
+ -0012 
1883 
1-8023 
1887 
1-8091 
4 
+ -0017 
Greenwich 
1883 
1-81 no 
1885 
1-8156 
2 
+ -0028 
1883 
1-8100 
1886 
1-8157 
3 
4- -0919 
