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



"The question of the mechanical deviation of the compass has mate- 

 rially changed its aspect of late years. Before that time the deviation of 

 a properly placed standard compass was of moderate amount, its maximum 

 seldom exceeding 20°, and the directive force which acted upon it being 

 generally comprised within the limits of two-thirds and four-thirds of the 

 mean force. There was then* no difficulty and some advantage in dis- 

 pensing altogether with mechanical correction ; or, if mechanical correction 

 was employed, it was possible, at least in vessels which did not change 

 their magnetic latitude, to make the correction so complete that tabular 

 correction might be dispensed with. But in the present day it is fre- 

 quently impossible to find a position for the standard compass at which 

 the deviation and the variation of directive force do not greatly exceed 

 these limits. In such cases the application of magnets for the purpose of 

 equalizing the directive force on different azimuths becomes a matter of 

 necessity ; while at the same time the danger of trusting to mechanical 

 correction alone without ascertaining and applying the residual errors is 

 increased. 



"This change of the condition of the question has produced a corre- 

 sponding change in the practice in the Royal Navy. 



" The same care as before is still used in the selection of a place for the 

 standard compass ; but a magnet is frequently or generally introduced for 

 the purpose of equalizing the directive force on different azimuths, and at 

 the same time diminishing the semicircular deviation. The quadrantal 

 deviation is not often corrected mechanically, but is generally left for 

 tabular correction. 



" The heeling deviation is always ascertained, and is sometimes corrected 

 mechanically. " 



After the ' Glenorchy ' was swung she took in an additional quantity 

 (about 120 tons) of iron. I do not, however, think it possible that this 

 quantity could have altered the deviations sensibly. 



The ( Glenorchy' sailed from Greenock on the 25th of December. She 

 had on board a pilot accustomed to the navigation of the Irish Channel. 

 She was towed to Lamlash Harbour, in the Island of Arran, where she 

 lay till 3 a.m. on the 31st of December. She then got under way, the 

 wind blowing moderately from the N.W., and steered a course down mid- 

 channel, sighting the Copeland, the Mull of Galloway, the North and 

 South Rock, St. John's Point, and the Calf of Man lights. 



The wind gradually heading her, she tacked about 6.15 a.m. on the 

 1st of January. At 7.10 a.m. her position was determined by a bearing 

 and distance of the South Stack Light, which then bore S. by W., distant 

 five miles. 



Till the ship tacked she had been on the starboard tack, on courses 

 from S.W. to S., on which the deviation-card gave small deviations for the 

 steering-compass. The bearing of the lights successively passed had, 



