500 STAFF CAPTAIN EVANS, E.N., ON THE CHANGES OF POLAE MAGNETISM 
General Table. — Her Majesty’s Ship Northumberland. 
Northumberland, 
(6621 tons), 
26 guns, 
1350 horse-power. 
Iron hull, 
iron-plated. 
Armour 
bulk-heads. 
Rifle-tower on 
quarter-deck. 
Built at Millwall, 
River Thames ; 
head N. 39^° E. 
magnetic. 
Plated on Stocks. 
Launched 
April 17, 1866. 
Compass. 
Poop. 
On Stocks . . .Mar. and Apr. 1866 
Off Deptford.. Apr. 19, 1866... 
Sheerness Jan. 1, 1867 ... 
Sheemess Jan. 26, 1867 ... 
Sheerness Feb. 28, 1867 ... 
Sheerness.. March 2, 1867 
Devonport ...June 26, 1867... 
Devonport ...Aug. 29, 1867... 
Devonport ...Dec. 10, 1867... 
On Stocks . . .Mar. and Apr. 1866 
Off Deptford.. Apr. 19, 1866. 
, In 
Victoria 
Docks. 
( Apr. 21, 1866. 
May 29, 1866. 
I July 12, 1866. 
' Aug. 10, 1866. 
Sept. 1, 1866 . 
Oct. 24, 1866 . 
l^Dec. 17, 1866. 
Sheerness Jan. 1, 1867 
Sheerness Jan. 26, 1867 . 
Sheerness Feb. 28, 1867 . 
Devonport . . .June 26, 1867 . 
Devonport ...Aug. 29, 1867. 
Devonport ...Dec. 10, 1867 • 
Devonport ...Dec. 10, 1867 . 
Approximate coefficients. 
+0 50 
\e point . . 
-36 53 
+ 4 35 
+ 7 02 
+ 1 12 
-36 13 
+ 7 02 
+7 22 
+0 01 
-36 13 
+ 7 09 
+7 19 
-0 14 
-4 55 
+ 0 14 
+7 13 
-0 24 
-0 35 
+0 59 
+1 15 
By deviation, horizontal and vertical forces 
point. Ship in dock, head S. 84° E. magnet 
Exact coefficients. 
By deviation and forces on one point . 
From swinging through a Quadrant . 
By deviation and forces on one point (head S. 
magnetic). Two iron-plated ships alongside, 
machinery, iron masts, dfc., placed on board 
this interval 
-48 43 
+ 15 13 
+5 55 
-0 35 
- 3 16 
+12 20 
+5 39 
—0 48 
- 3 5i 
+13 59 
+6 07 
+0 29 
+1 15 
+2 14 
+0 35 
By deviation, horizontal and vertical forces 
point. Ship in dock, S. 84° E. mag's 
21 
£ 
3) 
<S 
' r 
-■157 
+•427 
+T33a 
1 
-•004 
+•416 
+-133a 
+•015 
-•646 
+•071 
+•122 
-•007 
+•021 
-•637 
+ T08 
+•128 
-•010 
+•001 
-•637 
+ ■110 
+ 127 
+•017 
-004 
-091 
+ •004 
+•126 
+•022 
I 
-•576 
+•277 
+ T23a 
m one 1 
-•569 
+•256 
+T20a 
“ J 
-•593 
+•329 
+T20a 
f 
-■788 
+•358 
+-090a 
1 
-•801 
+•361 
+'104a 
f 
-■877 
+•296 
+-090a 
1 
-•890 
+•291 
+T04a 
-•800 
+•135 
+-090a 
-•742 
+•129 
„ 
22° W. 
-•900 
+•075 
„ 
Steam ' 
during 
-•821 
-•842 
+ 099 
+•076 
" 
-•814 
+ 003 
„ 
, 
-•825 
+•025 
„ 
+ 022 
-•803 
+•228 
+•103 
-010 
+•039 
-•059 
+•203 
+•098 
— •014 
+•010 
—•070 
+ •230 
+•107 
+•008 
J 
-•153 
+•36° 
+"iooa 
on one 1 
/ l 
-•340 
-•215 
+•365 
+•541 
” 
1 
— •221 
+•516 
+-n 7 a 
Note . — The coefficients marked (a) are assumed Talue*. 
