l^JTPtODUCTION'. 4.9 



objects. Above all, do not fail to seize the moment 

 when a new cape projects from behind another, or 

 retires behind another point of land. While tiiis 

 is doing, you must endeavour, by setting the com- 

 pass as accurately as possible, to determine the 

 direction of both capes, not forgetting to note also 

 the time of this observation. The results thus 

 obtained have the great advantage, that they are 

 independent of all errors in the determination of 

 the ship's place. 



3. It is of equal importance to observe the mo- 

 ment, when one of the objects to be determined 

 appears in one of the four cardinal points, — east 

 or west, south or north. In the first case, if a de- 

 termination of the latitude can be combined with 

 this observation, the latitude of that point, at least, 

 is secured. Or, if an object passes through the true 

 north or south point, you must not neglect, if the 

 weather is clear, to take solar altitudes to deter- 

 mine the longitude by the chronometer. Neither 

 must it be forgotten, that, in fixing the cardinal 

 points, regard must be had to the variation of the 

 magnetic needle ; and it is advisable to note the 

 time by the time-keeper. 



4. It must not be neglected, on the succeeding 

 stations, to measure angles by objects, the position 

 of which has been previously determined by the 

 intersection of the angles. It is not only useful 

 to confirm, or to correct the situation of a point 

 by a new line of intersection j but such angles, 



VOL. I. E 



