40 Mr. J. Lilley on the Action of Compasses in Iron Ships. [Marcli 8, 



veuient manner for taking observations without the aid of compensating 

 magnets. By this compass alone should the ship be navigated ; the 

 steering-compass is simply the helmsman's guide. Many iron ships have 

 been fitted with two navigating binnacles, the one for steering, and the 

 other at the fore part of the poop, both furnished with compensating 

 magnets, and obviously both subject to the same changes incident to the 

 change of hemisphere; cases of ships thus fitted have come under the 

 author's notice, in which many providential escapes from wreck have 

 occurred on the return passage from India ; in one particular instance, land 

 was made on the coast of Ireland when the commander imagined he was 

 entering the channel, an error that could not have arisen had the ship been 

 furnished with an uncompensated standard compass instead of a compen- 

 sated compass. 



In the uncompensated compass, the changes of deviation are far less than 

 would be found in a compensated compass placed not more than 2 feet 

 above iron beams. Very full directions on this subject will be found in 

 the valuable work of the late Capt. E. J. Johnson, E^.N., and it is much to 

 be regretted that this work is not more studied by commanders and ofiicers 

 of iron ships. 



3. Frequent disasters have been found to occur in consequence of allow- 

 ing the compass to be too long in use without due examination, more par- 

 ticularly in steam-vessels going short voyages ; the author is led to this con- 

 clusion from the fact of having readjusted iron vessels' compasses stated to 

 be largely in error, but subsequently found, on swinging the ship, to have 

 a comparatively small error, the supposed error being referable to a 

 defective centre and pivot in the compass itself, which prevented the needle 

 from reaching its meridional position. In such cases an error of 8° or 10° 

 has been often observed; the importance of such an error in narrow 

 channels is too obvious to require comment. 



There are valuable and simple appliances which to a very great extent 

 remove this difficulty, and which are comparatively inexpensive ; it is to 

 be much regretted that a great indiiference to the state of vessels' com- 

 passes exists in the minds of those under whose care the compasses are 

 often placed, and who, it might be expected, would from experience have 

 been more sensitively alive to the absolute necessity of keeping the com- 

 passes, as far as possible, in a state of efficiency. If a compass looks clean 

 upon its surface, it is believed to be in a perfect state, although it may have 

 been stowed away with the card upon the pivot without any protection, 

 thus interfering with the most important of its working parts ; as a conse- 

 quence, the card, when required for use, will be sluggish upon its pivot, and a 

 false indication of the direction of the vessel's head is an unavoidable result. 



4. A defective adjustment of the compass is again a vital source of 

 error. This mainly depends, 1, on the locality in which the vessel is 

 swung, which is too often a dock, where other iron vessels lie in dangerous 

 proximity ; 2, a want of due precaution on the part of the adjuster, in the 



