1865.] and on the Meteorological Department. 539 



case, that the causes of deviation of the compass in each individual ship 

 are numerous and dissimilar, and their effects proportionately varied. 

 In addition to the variety of effects due to the variety of causes, these 

 effects seem also to vary according to the build of the ship, the nature 

 and quality of the material of which she is built, and the direction of the 

 line of the keel during building, the nature, quantity, and stowage of the 

 cargo, the ship's course for the time being, her position in the water for 

 the time being, the magnetic hemisphere in which she may be, and the 

 varying distance of the ship from the magnetic equator. They vary, 

 too, it would seem, from time to time, according to the service on which 

 the ship may be or may have been employed, and with the age of the ship. 

 Science has undoubtedly done much to ascertain the laws that govern these 

 numerous causes of error ; but it is obvious, even from the tentative and 

 experimental process which the President and Council of the Eoyal Society 

 themselves suggest, and from the difficulty they find in preparing the 

 specific directions for which the Board of Trade have asked, that the remedy 

 is not capable of being reduced to fixed or simple rules, or of being enforced 

 without a large and experienced staff of scientific officers, or without an 

 amount of minute arbitrary and indeterminate supervision which would be 

 intolerable and impracticable. Moreover, so far as the Board of Trade can 

 learn, the highest authorities are not yet agreed as to the principle of 

 the remedy, the practice of the Admiralty, which receives the approval 

 of the Royal Society, being founded in the main on one principle, whilst 

 the practice of the Mercantile Marine is founded on another and different 

 principle, which is supported by no less an authority than the Astronomer 

 Royal. 



" In a letter from the Admiralty to this Board, dated 14th September 

 last, are enclosed some memoranda by Commander Evans, R.N., of the 

 Compass Department. Those memoranda the Royal Society indorse in 

 the printed memorandum enclosed in their last letter. In them it is stated 

 that the principal features of the system followed in Her Majesty's Navy 

 are, ' 1. By having in each ship a standard compass distinct from the 

 steering-compass * * * by which compass alone the ship is navi- 

 gated,' and ' 2. The requiring each ship to be swung and to be navigated 

 by a Table of Errors.' 



" On the other hand, the Astronomer Royal, in his syllabus of a course 

 of lectures delivered this year to the Royal School of Naval Architecture 

 and Marine Engineering, states that he ' has no hesitation in giving his 

 own opinion that the compasses used for directing the ship's course ought 

 to be corrected, and that the efforts of scientific men ought to be directed 

 mainly to the rendering this correction rigorously accurate and easy of 

 application.' 



" The Board of Trade have, as the President and Council of the Royal 

 Society are aware, already published and circulated Mr. Towson's work, 

 a work ' strongly recommended to nautical men ' by the Astronomer Royal, 



VOL. XIV. 2 S 



