NAVIGATION. 455 



training of professed steam engineers, in the whole theory, as well 

 as the practical use, of steam power : and next to this, the use of 

 boilers without return flues, or chimneys, passing through them ; 

 with additional safety valves ; and fusible plugs, which would melt 

 and let out the steam, when too much heated. All large sea vessels 

 should be provided with life boats, so built as to be incapable of 

 sinking, even when filled with water. 



CHAPTER VI. 



NAVIGATION. 



NAVIGATION is the art of conducting and managing vessels ; espe- 

 cially while at sea, or sailing from port to port. In this definition, 

 we include Seamanship, or the art of manoeuvring a vessel, by means 

 of the sails, anchors, and other appendages ; considering this as an 

 essential part of navigation, in its wider sense. The name is derived 

 from the Latin word navigatio, of the same meaning ; and this 

 from the Latin, navis, or the Greek vavs, a ship. Navigation depends 

 on the principles of Mathematics and Astronomy, Physical Geogra<- 

 phy and Meteorology : and the sailing of vessels involves a peculiar 

 class of problems in Mechanics. In connection with ship building, 

 this art has been, and still is, one of the mightiest agents of com- 

 merce and civilization. It has rendered oceans, which would other- 

 wise have been impassable, the great highway of nations ; and the 

 source of vast riches, from their extensive fisheries, and their sub- 

 marine productions. The subject of JEronautics, or the navigation 

 of the air, by means of balloons, has perhaps more relations to this 

 branch than to any other; though it is a subject of minor import- 

 ance. 



Among the ancient nations, the PhoBnicians were the most skilled 

 in Navigation ; and they are said to have directed their course by 

 the stars, as early as 1630 B. C. Their voyages were mostly con- 

 fined to the Mediterranean, and the neighboring seas ; though some 

 writers believe that one of their vessels circumnavigated Africa. The 

 construction of maps was the greatest step attained by the ancients, 

 in advancing the art of navigation. This art was revived, in modern 

 times, by the rich commerce of Venice and Genoa with the eastern 

 coasts of the Mediterranean. The invention of the Mariner's Com- 

 pass, aided Vasco de Gama in discovering a southern passage to 

 India ; and guided Columbus to the discovery of a New World; thus 

 enhancing the importance of Navigation, and stimulating others to 

 its improvement. 



The log line was introduced, about the year 1570, to measure the 

 rate of a ship's sailing; and in place of the Astrolabe, with circular 

 rings, and the Arbalete, or cross staff, for finding the altitudes of 

 celestial bodies, the Back staff, invented by Davis, about 1600, and 

 sometimes called Davis's quadrant, furnished a better method ; until 

 the introduction of Hadley's, or more properly Godfrey's Quadrant, 



