the Manner's Compass. 371 



means, be directed to their corresponding points in the 

 heavens, and the mariner will know that he is really sailing 

 upon the rhumb indicated by the cord. 



I am hiclined to think that a seaman may sometimes be 

 ^liable to error, in the continual reference which it is neces- 

 sary for him to make to the variation oF the compass, from 

 a possibility of his allowing it on the wrong side, by sub- 

 tracting where he should add, or by adding where he should 

 subtract it : even under a supposilion that such a mistake 

 is not likely to occur, the use of this instrument as an 

 additional check, in a mnlter of so much importance as is 

 the ascertaining of a ship's course, may not be entirely un- 

 worthy of attention. 



It is very probable, that from my imperfect information 

 upon these subjects, I am now proposing what has before 

 been suggested, and been found either to be wholly im- 

 practicable, or of little or no utility when reduced to prac- 

 tice. This is indeed the more probable from the extreme 

 simplicity of the expedient itself, which could scarcely have 

 escaped the attention of the many enlightened seamen, and 

 others, who have devoted their minds to subjects of this 

 nature. This consid;;ration, however, is not sufficient to 

 induce me to lose a chance of suggesting any the most 

 triflinn' hint which may be useful to a class of men to 

 whom we are so much indebted. 



It may be objected against the application of this princi- 

 ple to a ship's compass, that as the variation in a long voy- 

 age is continually changing, the card in a short time after 

 it has been adjusted will not point trulv. This must be 

 admitted; but it must also be recollected that it will agree 

 with the last variation ascertained, and which is that on 

 which the mariner must rely, until a fresh observation shall 

 liave been taken. 



It may also be objected, that through the negligence of 

 the persons employed to regulate this instrument, errors 

 may arise, equal to those which it is intended lo obviate ; 

 but surely, whatever may tend to afford a correct knowledge 

 of a ship's course, is of sufficient importance to render the 

 adjustment of the card an office by no means unworthy of 

 the captain himself; and it cannot be supposed that he, 

 or indeed any other officer, can be liable to error in an ope- 

 ration merely manual. 



If we admit, however, that these objections are well 

 founded, an iusiiumenl of this description might not be 

 destitute of utility, placed in the captain's cabin, or some 

 ptlier convenient part of the ship, where it might contiiui- 



ally 



