( 303 ) 



No. XLIX. 



Description and use of a neio and simple Nautical Chart, for tvork- 

 ing the different problems in Navigatum; with examples of its 

 application according to Mercatofs Suiting, and sailing by the 

 Arc of a Great Circle; with a demonstration of its principles. 

 By John Garnclt, of New Brunswick, New Jersey, 



"Sign iles irritant animos demissa per aarem, 

 " §h a ., r/uce sunt oailis subjecta jidelibus, et quce 

 " lp.se sibi tradit spectator.' 1 '' 



(fcj To the Author of this Communication an Extra-Magellanic Pre- 

 mium oi a Gold medal was awarded by the Society. 



Read August 25th, 1807. 



THIS Chart is a partial projection of a portion of a spher- 

 ical or spheroidal surface, containing in length the different de- 

 grees of latitude, and in breadth as many of longitude as are 

 found necessary. The parallels of latitude are projected into 

 right lines, parallel and equidistant to each other, (the reason of 

 which will plainly appear in the demonstration of the principle 

 at the end;) and are divided into degrees of longitude by a scale 

 of equal parts, according to the length of each degree at 

 different latitudes, either in the sphere or spheroid, or by Ta- 

 ble T of the Requisite Tables.* — Through these divisions the 

 different meridians are drawn or engraved, on both sides the 

 Central Meridian, which is always a right line. — Vide chart. 



The Index (which is separate) contains all the courses in 

 the quadrant of a circle, both in degrees, and quarter points, 

 and also the distance sailed as far as necessary; in using it, the 

 chief attention requisite is to peace the center C of the (juadrant 

 on that point in any given parallel oj latitude, from which the 

 distance sailed shall subt.-nd nearly\ an equal difference of 

 longitude on each side the Central Meridian or middle line of 



* Gavnett's Requisite Tables. 



■j-Itis not necessary that it should be exactly so, as the beginning of the distance, or 

 Centci C, had belter be placed on an engraved meridian, so that the difference of longitude; 

 may be seen at one Yicw at the other extremity of the distance, 



R 



