336 
THE ASTRONOMER ROYAL’S MAGNETICAL OBSERVATIONS IN 
Proceeding now Avith the forces in the horizontal plane at each of the tube stations, 
the total horizontal force at each station is given by the formula 
( time of 20 vibrations in normal local elementsX 2 
time of 20 vibrations at the station J ’ 
of which quantity the logarithm only is used ; the longitudinal force at each station = 
horizontal force at station X cos disturbed azimuth, and the transversal force to the 
right = horizontal force at station X sine disturbed azimuth. The comparison of these 
Avith the longitudinal and transversal forces derived from the normal local elements 
gives the disturbances of magnetism in both directions at each station. Thus the fol- 
loAving Table is formed : — 
Forces in the Horizontal Plane at each Tube station. 
Nos. of 
Stations. 
Description of Stations. 
Disturbed 
azimuth. 
Logarithm 
of total 
horizontal 
force. 
Longi- 
tudinal 
horizontal 
force. 
Transversal 
horizontal 
force. 
Longi- 
tudinal dis- 
turbance. 
Trans- 
versal dis- 
turbance. 
2, 20. 
3, 19. 
4, 18. 
5, 17. 
6, 16. 
7, 15. 
8, 14. 
9, 13. 
10, 12. 
Carnarvon Abutment 
Middle of Carnarvon Land Tube... 
Carnarvon Land Tower 
Middle of Carnarvon Water Tube.. 
Britannia Tower 
Middle of Anglesey Water Tube... 
Anglesey Land Tower 
Middle of Anglesey Land Tube ... 
Anglesey Abutment 
o in 
- 3 21 15 
- 1 7 15 
- 0 21 40 
+ 3 3 45 
- 1 9 10 
- 2 32 55 
- 0 15 25 
- 3 42 30 
- 2 3 20 
040958 
9-92620 
9 86538 
9-92282 
976076 
9-98458 
9'86626 
9-84000 
0-32254 
+2-5635 
+0-8436 
+0-7335 
+0-8360 
+0-5763 
+0-9642 
+0-7349 
+0-6904 
+2T002 
+01502 
+00165 
+00046 
-00447 
+00116 
+00429 
+00033 
+00475 
+0 0754 
+ 1-6050 
— 0 1149 
-0-2250 
-01225 
-0-3822 
+0-0057 
-0-2236 
-0-2681 
+ 1-1417 
— 0 1348 
-02685 
-0-2804 
-0-3297 
-0-2734 
-02421 
-0-2817 
-0-2376 
-0 2096 
23, 25. 
22, 26. 
21, 27. 
Chester Tower 
Middle of Conway Bridge 
Holyhead Tower 
- 31 1 15 
-146 36 15 
- 15 40 50 
9-71754 
9-51892 
9-86174 
+0-4472 
-0-2758 
+0-7003 
+0-2689 
+0-1818 
+0-1966 
+0-5397 
-01832 
+0-7928 
-0-7268 
-08139 
-0-7991 
The principles of the treatment of the vertical forces are similar. The vertical force 
at each station is found by the formula, total horizontal force at station X tan disturbed 
dip ; and the vertical disturbance is the difference betAveen this number and the vertical 
force in the first Table. Thus the following Table is formed : — 
Vertical Force at each of the Tube stations. 
Nos. of 
Stations. 
Description of Stations. 
Distui’bed dip. 
Vertical force. 
Vertical 
disturbance. 
2, 20. 
3, 19. 
4, 18. 
5, 17. 
6, 16. 
7, 15. 
8, 14. 
9, 13. 
10, 12. 
Carnarvon Abutment 
Middle of Carnarvon Land Tube . . . 
Carnarvon Land Tower 
Middle of Carnarvon Water Tube . . . 
Britannia Tower 
Middle of Anglesey Water Tube 
Anglesey Land Tower 
Middle of Anglesey Land Tower 
Anglesey Abutment 
- 1 24 22 
+ 10 35 45 
+ 8 46 0 
- 0 47 57 
- 1 1 34 
- 1 11 35 
- 9 10 22 
+ 16 27 37 
+26 9 34 
-00630 
+01578 
+0 1131 
-00117 
-00103 
-00201 
-0-1187 
+0-2044 
+ 1 0322 
-2-7452 
-2 5244 
-2-5691 
-2-6999 
-2-6985 
-2-7083 
-2-8069 
-2-4838 
-1-6560 
23, 25. Chester Tower 
22, 26. Middle of Conway Bridge 
21, 27. [Holyhead Tower 
+39 51 26 
+25 23 52 
+42 20 0 
+0-4357 
+0-1568 
+0-6626 
-2-1809 
-2-4598 
-1-9540 
Finally, in order to obtain results which appear to possess more of a physical character, 
we shall assume that each of the disturbances (longitudinal, transversal, vertical) is pro- 
