456 ARCHITECHNICS. 



invented by Godfrey, of Philadelphia, in 1730. Prince Henry of 

 Portugal, revived the use of plane charts, to mark and indicate a 

 ship's course : but the mode of allowing for the earth's sphericity, 

 or the convergence of the meridians, was successively improved by 

 Nunes or Nonius of Portugal, in 1537 ; by Mercator of Belgium, in 

 1569 ; and by Wright of England, in 1599. The invention of 

 logarithms, by Napier, in 1614, and of Gunter's scale, in 1620, 

 greatly facilitated nautical calculations : and the more exact measure- 

 ments of the earth, and improved astronomical tables, of later times, 

 have farther benefitted the art of Navigation. The British govern- 

 ment, in 1763, rewarded Mayer for his new Lunar Tables, with a gift 

 of 3000; and, in 1765, it awarded 10,000 to Harrison, for his 

 invention, in the preceding year, of a Chronometer, sufficiently 

 accurate to serve for finding the longitude at sea. 



The principal topics of Navigation, may be comprehended under 

 the heads of Seamanship ; Dead Reckoning; and Astronomical Navi- 

 gation, or Nautical Astronomy. 



1. Seamanship, is the art of sailing a ship ; chiefly by managing 

 the sails and rigging, so as to conduct it on the desired course, and 

 preserve it from danger. The rigging of vessels, we have already 

 described, as far as there was room, in the preceding branch. A 

 ship, when in harbor, is either attached to some object on shore, by 

 a strong rope called a halser ; or is secured at a distance from shore, 

 by one or more anchors, let down upon the bottom of the sea, and 

 to which the vessel is attached by strong ropes, or chains, called 

 cables. When a vessel heaves up her anchors, or casts off her 

 fastenings, and hoists sail, to change her position, she is said to get 

 under weigh. The left side of a vessel is called the larboard, and 

 the right, the starboard side ; and the side turned from the wind is 

 also called the leeward. A stiff vessel, is one which will not easily 

 overturn ; in contradistinction from a crank one. 



A ship sailing with the wind, that is, in the direction in which the 

 wind blows, is said to have the wind aft, or to sail before the wind. 

 When it blows crosswise of the ship, she is said to have the wind 

 abeam ; that is, against the beam ends, or sides. In this case, the 

 sails are placed obliquely to the wind, which thus exerts a force to 

 move the vessel at right angles to its own direction. When the 

 wind comes from a point still more ahead, the ship is said to be 

 close hauled ; and by having the sails very oblique, most vessels can 

 sail towards the point from which the wind blows, within 4 or 6 

 points, that is, 45 or 673. In this case, they sail slower, and 

 make more leeway ; drifting sideways with the wind, and falling off 

 from the course on which they strive to sail. In order to approach 

 a place to the windiuard, a vessel must frequently tack ; sailing as 

 directly as possible towards the place, but inclining alternately to the 

 right and to the left of it, at each tack or turn. 



Vessels always tack by turning their head towards the wind, and 

 bracing the sails obliquely, to aid the turning, till the wind comes 

 sufficiently on the other quarter ; when the sails which act favorably 

 are said to draw. To gibe a fore-and-aft sail, is to turn it so that it 

 may receive the wind on the opposite side ; and the same object is 



