322 POPULAR LECTURES AND ADDRESSES. 



steer ; and thus, even if importance is attached to 

 the saving of minutes on the whole passage, this 

 will be promoted by taking time to correct the 

 compass. 



APPENDIX A. 



AN ADJUSTABLE DEFLECTOR BY MEANS OF WHICH 

 THE COMPASS ERROR CAN BE COMPLETELY 

 CORRECTED WHEN SIGHTS OF HEAVENLY 

 BODIES OR COMPASS MARKS ON SHORE ARE 

 NOT AVAILABLE. 1 



^Being extract from United Service Institution Lecture, 

 1878.] 



ABOUT thirty years ago, Sir Edward Sabine 

 gave a method, in which, by aid of deflecting 

 magnets properly placed on projecting arms at- 

 tached to the prism circle of the Admiralty 

 standard compass, a partial determination of the 

 error of the compass could be performed at any 

 time, whether at sea or in harbour, without the aid 

 of sights of heavenly bodies or compass marks on 



1 A very complete account of the deflector in theory and practice 

 is contained in a work by Captain Collet, of the French Navy, 

 entitled, Traite Thtorique et Practique de la Regulation et de la 

 Compensation des Com pas avec ou sans Rettvements (Challamel 

 Aine, Paris), which has been translated into English by William 

 Bottomley (Griffin, Portsmouth). 



