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XVIII. On the Changes which take place in the Deviations of the Standard Compass 
in the Iron Armour-plated, Iron, and Composite-built Ships of the Royal Navy, 
on a considerable change of Magnetic latitude. 
By Staff Commander E. W. Creak, R.N., of the Admiralty Compass Department. 
Communicated by Sir Frederick J. O. Evans, K.C.B., Hydrographer of the 
Admiralty. 
Received March 1,—Read March 15, 1883. 
The period comprised between the years 1855-68 was one of active research into the 
magnetic character of the armour-plated and other ships of the Royal Navy and the 
iron ships of the Mercantile Navy. 
It will be remembered that the Transactions of the Royal Society are rich in 
contributions to this important and interesting subject; important in a practical 
sense to the navigator, and of great interest as a subject of intelligent inquiry. 
Among these contributions was a paper read before the Royal Society in March, 
1865, “ On the Magnetic Character of the Armour-plated ships of the Royal Navy, 
and on the effect on the compass of particular arrangements of Iron in a ship,” by 
Frederick John Evans, Esq., Staff' Commander, R.N., F.R.S., and Archibald 
Smith, Esq., M.A., F.R.S. This paper contained the earliest published results of the 
system of observation and analysis of the deviations of the compass in the ships of 
the Royal Navy, which, established in 1861, has been carried out to the present day. 
These results showed the magnetic character of the several ships named, from the 
time of launching until fully equipped and at sea, and also an analysis of the semi¬ 
circular deviation of those ships which had made short voyages abroad. But the 
change of magnetic latitude through which the ships passed was so small, and the 
alternative of heeling the ships in one latitude so difficult, that the authors of the 
paper were unable to ascertain any but approximate values of the proportions of hard 
and soft iron affecting their compasses. 
The authors write : “ The determination of the proportion of the semicircular 
deviation, or rather of B, which arises from vertical induction in soft iron, and that 
which arises from the permanent or sub-permanent magnetism of hard iron, is a 
matter of great interest. Theoretically it may be determined in two modes, either 
by observing the deviation in two different magnetic latitudes, or by observing the 
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