1865.] of the Iron-built Armour-plated Ship' Pervemtz: 187 



arrived in England a few days before the launch, and immediately under- 

 took the observation of the deviation and the horizontal and vertical force 

 at various selected positions in the ship. These were the following, viz. 

 five positions on the upper deck, about 4 ft. 6 in. above the deck, distin> 

 guished as b, c, d, e, f, going from stern to bow ; b abaft the mizen-mast, 

 c immediately before the mizen-mast, d before the main-mast, e about the 

 middle of the length, and f before the fore-mast : three on the main deck, 

 ff, k, I; g halfway between the mizen and mainmasts, k below d, and I 

 below/: two in the hold, near the centre of the ship, m and n : b being 

 near the place where the neutral plane or rather the surface separating the 

 part of the ship which displayed north magnetism from that which displayed 

 south magnetism intersected the deck, was selected as a place for the 

 standard compass, and a place was prepared for it by making there a false 

 hatchway or compass platform, by replacing an iron beam by a wooden beam, 

 and substituting wood planks for iron plates at that part of the deck. 



6. From the observations, using the notation of the ' Admiralty Manual' 

 (which has been translated into Russian by the author for the use of the 

 Imperial Navy), by estimating the value of 2) and X, and making use of 

 the formulae of the Manual, 2nd edit., p. 110, 





the author obtained from the observations made the following results : 



7. These show 



(1) The small deviations on the stocks of the compasses in every 

 position, except near the north end of the ship, where, probably from the 

 armour-plating not being fixed, irregular deviations were to be expected. 



2p 



