4$. REPORT — 18G1, 



special character of tlie sliip lias been introduced, namely an iron-cased tower of 

 rather considerable dimensions for holding liflenien, and of sufficient thickness to 

 withstand the fire of heavy ordnance. This tower is placed on the quarter-deck, in 

 the neighbom-hood of the steeling- wheel. 



The magnetic character of the ship, as developed by the two compasses — before 

 the rifle-tower was fixed — is quite in accordance with the received principles as 

 due to the direction of the ship's head in building with reference to the magnetic 

 :peridian. The foremost compass, which is about ^rd of the ship's length from the 

 bow, had on the 10th of August last a maximum deviation of 16°, and the fifter 

 compass, wliich is about J-rd of the ship's length from the stern, a maximum deviation 

 of 31°, the sliip being built within .3° of the magnetic meridian (head N. 3° E.), and 

 the points of no de^-iation consequently at north and south. The deviation of the 

 after-compass had lessened 6° on the 24th of August, at which date the casing of 

 tlie iron rifle-tower had commenced. 



,, But it is not to these points I wovdd now chiefly direct your attention, but to 

 certain necessities arising from the novel structm'e of the ship, demanding, in so 

 far as the .compasses are concerned, serious attention. 



' In the fighting ships of what now may be tenned a past generation, we did not seek 

 for or expect invulnerability. In 1861 we demand nothing less, and " more iron " is 

 the ciy. It is clear from these new conditions that one compass at least, on which 

 the ultimate safety of the ship may depend, should be equally protected fi-oni the 

 fire of the enemy, in the event, which would most likely happen, of everything 

 Standing on the upper deck being swept away by the fire of the enemy. 



For the management of the ' WaiTior ' under this probable contingency, an addi- 

 tional steering-wheel has been fitted within the great armour-protected space on 

 the main deck : this space I need scarcely infomi you is cut off from the ends of 

 the vessel by massive iron bulk-heads. \\'^e are thus obliged, without reference 

 to choice of position, to place a compass near this steering-wheel on the main deck, 

 and suiTounded by iron of massive character on every side, and above as well as 

 below. 



Under these circimistances we coidd not but expect deviations of an exaggerated 

 amount, and particiUarly, from the large amoimt of horizontally placed iron from 

 the two iron decks and their beams, a large quadrantal deviation. 

 '• From the few obseiTations I have been enabled to make, owing to the constant 

 progress of the fittings, this quadi-antal deviation on the main deck is about 12°, 

 nearly ti-ebling in value quantities I have had to deal ■with in the other iron ships 

 of the Royal Na\y. 



. It must be familiar to those who have practically dealt with the subject of cor- 

 recting ship's compasses by the antagonistic influences of magnets and soft iron,- 

 that 12° of quadrantal deviation is an enonnous amount to deal with ; and that 

 the emploj-ment of soft iron coiTectors which might be usefully emjiloyed in the 

 smaller values, becomes open to grave objections for the larger ones. 



I have adopted for the ' Warrior's ' main-deck conijiass the plan therefore alluded 

 to by Mr. A. Smith, namely the compass cards on I\Ir. Smith s plan, and two com- 

 passes so placed close together as to destaroy by their mutual action this 12° of 

 quadrantal deviation, and correcting the polar magnet or semicu'cular deviation 

 by owe system of magnets placed in a vertical plane below, and in a central line 

 between the two compasses, so that both are equally coiTected at the same time. 

 At the time of my observations this semicircular deviation was 3^ points, or nearly 

 40° at the maximmu. 



I venture to hope that we have by this method overcome the more serious diffi- 

 culties of disembarrassing the mifortimate compass, which is now so tortured in its 

 action by the never-ending intiX)duction of iron of all shapes, sizes, and quality 

 aroimd it ; but I feel that imceasing vigilance is more than ever requii-ed in watching 

 the compass imder these conditions, and that the subtle agencies of the forces we. 

 employ will elude the control of imskilled hands. 



The greatest difficulties I have experienced in making certain preliminary expe- 

 riments, and what must happen practically in dealing with large compass devia- 

 tions, are those due to delicacy of manipulation and workmanship : for example, the 

 lubber lines of the compasses must be placed exactly parallel, and exactly in the 



