52 INTRODUCTION. 



an object appeared in the magnetical or in the 

 true meridian of the ship, or in the east and west 

 points, which may serve either to determine the 

 point itself, or, if its situation be ah'eady made out, 

 to correct the ship*s route as laid down. Of the 

 same use are the angles, measured according to 

 known objects ; of which there must be, at least, 

 two. To make use of them for determining the 

 place of the ship, draw, on very transparent paper, 

 from a point, the three lines that inclose these 

 angles, and move the paper about upon the plan 

 till the three lines of sight intersect the three 

 points in question at once. The centre of these 

 angles is the ship's place. Instead of two angles, 

 more may be employed with advantage in the same 

 manner. This method is more accurate, in pro- 

 portion as the objects are correctly determined, 

 from which the angles are measured, and the 

 nearer the angles themselves are to right angles. 



After a sufficient number of points is deter- 

 mined in the chart, the sketch of the coast, and 

 the direction and distribution of the mountains are 

 inserted by the eye ; in doing which, the profile- 

 drawings, mentioned above, are a great help to the 

 memory, which is confused by the continually new 

 forms of the land. It is also advisable, even before 

 the plan is made, which must often be deferred, on 

 account of the rapid increase of the labours of sur- 

 veying, to make a slight stereographic sketch of 

 the bendings of the coast, and of the ramifications 



