500 Anniversary Meeting. [Nov. 30, 



' Phil. Trans.' for 1843, 1844, and 1846. Instances occurred during the 

 Survey, and are recorded in the account, in which (although these were 

 not iron ships) the difference of the pointing of the compass on different 

 courses exceeded 90 ; the differences almost entirely disappearing when 

 Mr. Smith's formulse were applied. 



The assistance which, from motives of private friendship and scientific 

 interest, Mr. Smith had rendered to myself was, from like motives, con- 

 tinued to the two able officers who have successively occupied the post of 

 Superintendent of the Compass Department of the Navy ; and the formula 

 for correcting the deviation, which he had furnished to me, reduced to 

 simple tabular forms, were published by the Admiralty in successive edi- 

 tions for the use of the Royal Navy. 



As in the course of time the use of steam machinery, the weight of 

 the armament of ships of war, and generally the use of iron in vessels 

 increased more and more, the great and increasing inconveniences arising 

 from compass-irregularities were more and more strongly felt, and pressed 

 themselves on the attention of the Admiralty and of naval officers. 



An entire revision of the Admiralty Instructions became necessary. 

 Mr. Smith's assistance was again freely given, and the result was the pub- 

 lication of ' The Admiralty Manual for ascertaining and applying the De- 

 viations of the Compass caused by the Iron in a Ship.' 



The mathematical part of this work, which is due to Mr. Smith, seems 

 to exhaust the subject, and to reduce the processes by simple formulae and 

 tabular and graphic methods to the greatest simplicity of which they are 

 susceptible. Mr. Smith also joined with his fellow-labourer, Capt. Evans, 

 F.R.S., the present Superintendent of the Compass Department of the 

 Navy, in laying before the Society several valuable papers containing the 

 results of the mathematical theory applied to observations made on board 

 the iron-built and armour-plated ships of the Royal Navy. 



Owing in great measure to these researches, the system practised in the 

 Navy has been brought to its present advanced state. 



The outline of the system may be stated briefly as follows : 



1 . As regards the building of ships. It has been ascertained that the 

 amount of disturbance is greatest in iron ships which are built (in British 

 ports) with their heads to the North, and is still further and greatly 

 increased in armour-plated ships when they are plated with their heads in 

 the same direction in which they were built. It is therefore desirable 

 that iron ships should not be built with their heads to the north, and 

 that armour-plated ships should be plated in the reverse position to that 

 in which they were built. 



2. In respect to the fitting of ships. It is held to be essential that in 

 every ship a Standard Compass should be fixed in a position selected, 

 not for the convenience of the helmsman or of the builder, but for the 

 moderate and uniform amount gf the deviation at and around it, and 

 where every facility exists for the examination of errors, by comparison 



