410 



Mr. A. Smith on the Causes of the Loss of the [Apr. 29, 



standing on a wooden platform laid from the poop to the mainmast, and 

 about 15 feet abaft the mainmast, which was of iron. 



On the 18th of December the 'Glenorchy' had her compasses adjusted 

 in the Gareloch by Mr. Fleming in the usual way. 



The deviation of the steering-compass, as might have been expected 

 from the combined effect of the position of the compass in the ship and of 

 the ship in building, was enormous. Mr. Fleming says it was "as bad if 

 not worse than any he ever saw." Mr. Fleming informs me that before 

 magnets were applied to the steering-compass, when the ship's head bore 

 N. (magnetic) it bore S. by the steering-compass; when the ship's head 

 bore W. (magnetic) it bore about S.W. by S. by the steering-compass. 

 In other words, at N. (magnetic) there was a deviation 180°, at W. 

 (magnetic) a deviation of about 56° 15' E. The quadrantal deviation was 

 about 10°. 



These data give, using the notation of the 'Admiralty Manual for the 

 Deviation of the Compass,' 



13 = — 1-250, 

 €= 0, 



or a force of the ship to the stern exceeding by one-fourth the whole 

 directive force of the earth's magnetism acting on the compass, a disturbing 

 force about twice as great as that found at the steering-compass in any of 

 the iron-built armour-plated ships in Her Majesty's Navy. 



This enormous disturbing force was corrected by three large magnets 

 one of 36 inches and two of 26 and 28 inches placed together, fore and 

 aft, on the starboard side of the binnacle, and by two or three smaller 

 magnets placed so as to correct as far as possible the residual error on the 

 other cardinal points. 



The ship was then placed head N.W. (magnetic), when a westerly 

 deviation of three-fourths of a point 8° 26' was observed. This was of 

 course approximately the amount of the quadrantal deviation, and it was 

 corrected by a No. 12 iron jack-chain placed in the chain-boxes on each 

 side of the compass. 



The ship was then swung on sixteen points and the following deviations 

 of the steering-compass obtained ( + signifying that the N. point of the 

 needle was drawn to the E., — to the W.). 



'Glenorchy' Steering -Compass, December 18, 1868. 



Magnetic Course. 



Deviation. 



Magnetic Course. 



Deviation. 



N. 







S. 



—2° 



N.N.E. 



+3° 



s.s.w. 



4-3 



N.E. 



+7 



s.w. 







E.N.E. 



4-2 



W.S.AY. 







E. 



+3 



w. 



4-5 



E.S.E. 



-3 



W.N.W. 



-3 



S.E. 



-2 



n.w. 







S.S.E. 



-1 



N.N.W. 



9 



