NA VIGA TION. 27 



occasional regrinding, or by the substitution of a 

 fresh point for one worn blunt by sea use is 

 accurate enough for the most refined navigation, 

 and is perfectly convenient for use at sea, on 

 board of any ordinary wooden sailing ship, large 

 or small, in all ordinary circumstances of waves 

 and weather. 



23. If it were my lot to speak to you for a 

 whole evening on the subject of the mariner's 

 compass, I would have to tell you of the qualities 

 which the instrument must possess to render it 

 suitable for use in all ships, and all seas, and all 

 weathers, and of the correctors which must be 

 applied to it if it is to point correctly in iron 

 ships. To-night, I cannot for want of time. 

 [See articles on the compass below.] The azimuth 

 compass, for use at sea, is an ordinary mariner's 

 compass, with the addition of a simple appliance for 

 measuring the azimuths of celestial or terrestrial 

 objects on its card with great accuracy. 



24. GLOBES AND CHARTS. A celestial and ter- 

 restrial globe ought both to be found in every 

 school of every class. In navigation schools, much 



