PRESENT VARIATION OF THE COMPASS. 
323 
The accordance in the values of the annual change for the interval 1865-71 at the 
three observatories is very satisfactory. 
i 
Greenwich 7*95 
Kevv 8'08 
Stonyhurst 7*71 
From former investigations on this subject of the secular change of magnetic decli- 
nation* I was induced to consider that in the area included by the shores of the United 
Kingdom, the change was greater on its eastern than on its western side. A comparison 
of the lines of equal declination, as given on the annexed Chart (Plate XLYI.) for the 
Epoch January 1, 1872, with those given in the Phil. Trans, of 1870 for the Epoch 1842*5, 
by General Sir Edward Sabine, late President of the RoyalSociety, confirms the opinion 
I had entertained, as also that in the higher parallels of latitude of this area the change 
is greater than in the lower, — thus incidentally confirming the larger values found at 
Christiania by M. Hansteen as compared with those observed at Brussels by M. Quetelet. 
I have appended the details of this comparison of the lines of equal declination for 
the Epochs 1842*5 and 1872 ; but the following abstract brings more clearly to view the 
general character of the changes in the several geographical limits during the past 
thirty (29*5) years: — 
Annual decrease. 
Shetland Islands and N.E. coasts of Scotland, between 60th 
and 56th parallels 
East coast of England, 56th and 51st parallels 7*78 
South coast of England, 51st and 49th parallels. [Dungeness 
to Scilly, with the Channel Islands.] 
Greenwich Observatory 7*27 
Irish Channel, between 52nd and 54th parallels . . . . 7*10 
Ireland, S.W., West, and N.W. coasts, 52nd to 55th parallels 6*26 
Hebrides and West coast of Scotland, 56th to 58th parallels 6*85 
Included in the Stations given in this paper at which the magnetic declination has 
been observed within the last six years, are several at which observations had been pre- 
viously made either by Mr. Welsh in his Magnetic Survey of Scotland, 1857-58 (see 
Report of the British Association for the Advancement of Science, 1859), and which are 
reduced by corresponding observations at Kew to 1st January, 1858, or by Surveying 
Officers of II. M. Navy (see Report of the British Association for 1861, pp. 273-278), 
which observations are reduced to the 1st January, 1857, by similar corresponding Kew 
observations. 
We are thus enabled to obtain an approximate value of the amount of annual change 
for widely diverse localities in the United Kingdom, and to further test the recent acce- 
leration observed at Greenwich and Kew. 
* See Declination Map, British Islands, for the mean Epoch of 1st January, 1857, in Report on the Repeti- 
tion of the Magnetic Survey of England (Report of the British Association for the Advancement of Science, 1861). 
