622 
STAFF COMMANDER E. W. CREAK ON THE DEVIATIONS OF THE 
From the position of the standard compass in the “ Northampton” and “ Nelson,” 
83 feet from the stern, a positive value of c might have been expected; but there is a 
transverse armoured bulkhead, 8 inches thick, the top of which is 30 feet nearer the 
stern than the compass in each vessel, which is the probable cause of the minus sign 
for c. 
It is a subject for further inquiry as to what extent iron masts contribute to the 
values of c when the Standard Compass is placed near them. A series of experiments 
was made near Athens, where the magnetic dip is approximately 53° N., and at 
Singapore, in 13° S. dip, on board the “ Ruby.”* The Standard Compass of this ship 
is placed at 6 feet 9 inches from the iron mizenmast. The results showed that at 
three different parts of the mast (on a level with the compass, and a few feet above, 
and below that level) the effects of transient induction were very small, and that the 
mast acted almost entirely as a permanent magnet. 
The remaining constant of the semicircular deviation, f is one which has hitherto 
been accepted as zero, from the iron in the transverse section of the ships of the Royal 
Navy—except turret ships—being considered as placed symmetrically with respect to 
the Standard Compass. 
In the Table I., however, there are five ships for which values of f have been dis¬ 
covered, and one, the “ Triumph,” in which it reaches an amount which could not be 
disregarded in a forecast of that vessel’s deviation for any given geographical position. 
From Table I. the following values of f have been collected:— 
/• 
f 
i- tan 0 in England. 
Bellerophon. 
. . -'005 
-•012 = 0° 42' 
Triumph. 
. . —013 
-■038=2° 10' 
Swiftsure . 
. . +-004 
+ •010=0° 35' 
Active .... 
+ •010=0° 35' 
Himalaya . 
. . + -006 
+ •015 = 0° 52' 
Comus .... 
. . --004 
-•010=0° 35' 
From the peculiar construction of some of the later types of armour-plated ships 
the constant f will probably attain higher values than those hitherto experienced. 
Quadrantal deviation. 
(approximate value in degrees =D) is the maximum of quadrantal 
deviation from soft iron symmetrically placed. 
(approximate value in degrees = E) is the maximum of quadrantal 
L A. 
deviation from soft iron unsymmetrically placed. 
* These expei-iments were made by Navigating Lieutenant Henderson, R.N., of the “ Ruby.” 
Coefficient <£)= 
Coefficient (S = 
