CHARTS. 



the position of that place. In like manner 

 all the places on the coast are to be laid 

 clown and connected by observations 

 made on the coast : or if no sketch had 

 been previously made, the contour of the 

 coast is to be drawn agreeable to the best 

 charts. Meridians and parallels are to be 

 drawn through every fifth or tenth degree 

 of latitude and longitude, and extended 

 to the coast. 



A compass is to be inserted in some 

 convenient part of the chart, and the 

 points extended to the land : an anchor 

 is to be drawn where there is good an- 

 choring ground, and in places where it is 

 safe only to stop a tide, an anchor without 

 a stock is to belaid down. The soundings, 

 the quality of the ground, the times of 

 high water at full and change, &c. are 

 to be marked in their proper places. 



CHARTS, manner of itsi?ig. The princi- 

 pal use of a chart is, to find the course 

 and distance between any two places 

 within its limits, and to lay down the 

 place of a ship on it, so that the position 

 of the ship with respect to the intended 

 port, the adjacent land, islands, &c. may 

 be readily perceived. 



To find the latitude of a place on the chart. 



Rule. Take the nearest distance be- 

 tween the given place and the nearest 

 parallel of latitude, which being applied 

 the same way on the divided meridian, 

 from the point of intersection of the pa- 

 rallel and meridian, will give the latitude 

 of the proposed place. 



Example. Required the latitude of 

 Port Louis, in the isle of France. The 

 least distance between Port Louis and the 

 nearest parallel, being laid the same way 

 on the meridian, from the extremity of 

 that parallel, will reach to 20 8' S., the 

 latitude required. 



To find the course and distance between tivo 

 given places on the chart. 



Rule. Lay the edge of a scale over the 

 given places, and take the nearest dis- 

 tance between the centre of any of the 

 compasses on the chart and the edge of 

 the scale ; move this extent along, so as 

 one point of the compass may touch the 

 edge of the scale, and the straight line 

 joining the points may be perpendicular 

 thereto; then will the other point shew 

 the course; and the interval between the 

 places being applied to the scale will 

 give the required distance. 



Example. Required the course- and 

 distance from Cape St. Andre to Cape 



VOL. III. 



St. Sebastian, both in the island of Mada- 

 gascar. The edge of a scale being laid 

 over the two places, then, by moving 

 the compass as directed, the course will 

 be found to be N. E. E., and the in- 

 terval between them will measure 105 

 leagues. 



The course and distance sailed from a known 

 place being given, to find the ship's place 

 on the Chart. 



Rule. Lay the edge of a scale over the 

 place sailed from, parallel to the given 

 course; then take the given distance 

 from the scale on the chart, and lay it oft' 

 from the given place by the edge of 

 the scale, and it will give the point on 

 the chart representing the place on the 

 ship. 



Example. The correct course of a ship 

 from Cape St. Maria, on the north side 

 the entrance of the river La Plata, was 

 N. E. by E. and the distance 238 leagues. 

 Required the place of the ship on the 

 chart. The edge of the scale being laid 

 over Cape St. Maria, in a N. E. by E. di- 

 rection, and the distance 238 leagues, 

 laid off from Cape St. Maria by the edge 

 of the scale, will give the place of the 

 ship, which will be found to be in the la- 

 titude 23 15' S. 



To find the longitude of a place on the 

 Chart. 



Ride. Take the least distance between 

 the given place and the nearest meridian, 

 which being laid off on the equator, or 

 divided parallel, from the point of inter- 

 section of the parallel and meridian, will 

 give its longitude. 



Example. Required the longitude of 

 Funchal in the island of Madeira. The 

 least distance being taken between Fun- 

 chal and the nearest meridian,and laid off 

 from the intersection of that meridian 

 with the divided parallel, will give 17 & 

 W., the longitude required. 



To find the distance bet-ween tivo given places 

 on the Chart. 



1. When the given places are under 

 the same meridian. 



Rule. Find the latitude of each ; then 

 the difference or sum of their latitudes, 

 according as they are on the same, or on 

 opposite sides of the equator, will be the 

 distance required. 



Example. Required the distance be- 

 tween the nearest extremities of the is- 

 lands of Grenada and Guadaloupe. 



U 



