312 POPULAR LECTURES AND ADDRESSES. 



rectors for the semicircular error and the heeling 

 error must be adjusted from time to time to keep 

 the compass correct. 



Lastly it has an appliance for fixing on the for- 

 ward or after side of the binnacle a bar of soft iron 

 to realise conveniently a most important but long 

 strangely neglected correction, 1 given so long ago as 

 1 80 1 by Captain Flinders. This last appliance 

 has been very successful in ships of the Peninsular 

 and Oriental and Cape Mail Services. In the 

 Union Steamship Company's ship Durban (Captain 

 Warleigh), for instance, the first to which it was 

 applied in connection with my compass, an error of 



1 Fifteen ships are reported by the Liverpool Compass Com- 

 mittee as having had this correction applied to their steering com- 

 passes with more or less complete success, but in every instance 

 with decidedly good result. It was also applied with remarkable 

 defmiteness and success to a compass in the ss. City of Mecca, 

 by Captain Lecky, on a voyage between Bombay and the Clyde 

 some years ago. An error of 14, found in the -English Channel 

 on the east and west courses, after the compass had been perfectly 

 corrected .by Airy's method a few weeks previously on the magnetic 

 equator, was corrected by a vertical soft iron pillar, fixed to the 

 ship in the neighbourhood of the compass. The result, proved in 

 subsequent voyages of the ship, was most . satisfactory. I know no 

 other cases in which the Flinders process had been used in iron ships 

 before I commenced practising the process myself in 1878. 



