NAVEL 



into three parts. As such the nave 

 includes the choir and the height 

 of the clerestory, but when the 

 choir is shut off from the body of 

 the church, it is commonly ex- 

 cluded from the term nave. See 

 Basilica ; Cathedral ; Choir. 



Navel. Scar in the centre of 

 the abdomen, which marks the 

 spot where the umbilical cord en- 

 tered the organism during the 

 period of development in the 

 uterus or womb. 



Navigation. Art of directing a 

 ship from one position to another, 

 and of determining its position at 

 sea at any moment. A chart and a 

 mariner's compass are required. 

 Before the invention of the mari- 

 ner's compass, mariners were com- 

 pelled to keep in sight of land. 



In order to determine the course 

 between two positions, charts have 

 been drawn of different portions of 

 the globe. These charts have the 

 latitude and longitude and the 

 true or magnetic north marked on 

 them. The present position of a 

 vessel and the one it is desired to 

 reach are plotted on the chart, 

 which thus gives the course to be 

 made good. The direction of this 

 course is read off from the points 

 of the compass pointed on the 

 chart. To discover from the chart 

 the course to be steered in order to 

 arrive at any desired position, the 

 mariner must know the position of 

 his vessel. In sight of land this is 

 easily found by taking compass 

 bearings, i.e. the direction by com- 

 pass, of prominent objects such as 

 a lighthouse, or church spire. The 

 position of these objects is* shown 

 on the chart. Three or more 

 objects are selected, so that the com- 

 pass bearings cut one another at a 

 fairly large angle when shown on 

 the chart. Through each object on 

 the chart is then drawn the ob- 

 served compass bearing, and the 

 point where these lines cut is the 

 position of the ship at the time 

 of observation. 



For example, a mariner observes 

 that the summit of a hill bears 

 N.W., a church spire N. 10 W., 

 and a lighthouse N. 40 E. The 

 ship's position is where the three 

 lines cut as shown in the figure : 



When out of 

 sight of land, the 

 approximate po- 

 sition at any 

 time can be found by calculating 

 the number of nautical miles the 

 vessel has travelled along the course 

 from the last known position and 



5660 



then plotting this distance on the 

 chart. Such an approximate posi- 

 tion is called dead reckoning (D.R. ). 



The exact position of a vessel 

 when out of sight of land is 

 obtained by observation of the 

 heavenly bodies. Observations of 

 stars or planets give the most accu- 

 rate results, but can only be made 

 during the hours of darkness. They 

 are easily observed, as many are 

 usually visible at the same mo- 

 ment. The positions ascertained 

 by observations of the sun are, 

 however, not so accurate as those 

 obtained by the stars. 



A sextant and a chronometer 

 showing Greenwich time, or a 

 known error on Greenwich time, 

 are required for taking an obser- 

 vation. The altitude of the heaven- 

 ly body is measured by the sextant 

 and the time is noted at the instant 

 the altitude is observed. The 

 observer obtains the arcual dis- 

 tance of his position from the point 

 where, at the instant of observation, 

 an imaginary line joining the 

 centre of the earth and the heaven- 

 ly body cuts the earth's surface. 

 This imaginary point on the earth's 

 surface is known as the geographi- 

 cal position of the heavenly body. 

 The observer then knows that he 

 is on a circle whose centre is the 

 geographical position of the body 

 observed, and whose arcual radius 

 is the observed altitude. Another 

 circle can be 

 drawn for an- 

 other star ob- 

 served simul- 

 taneously, o r 

 for the same 

 body after an 

 interval of 

 time. The 

 ship's position 

 is then at one 

 of the points of 

 intersection of 

 the two circles. 



In practice 



Navigation. Diagram 

 showing the geogra- 

 phical positions X.Y, 

 of two heavenly 

 bodies, and A, B, the 

 points oi intersection 

 of circles giving the 

 position of a ship. 

 See text 



it is not usually 

 possible to draw the circles owing 

 to the excessive length of the radii, 

 so the following method is adopted. 

 The altitude is observed at any 

 moment and the Greenwich time 

 noted. The D.R. position is cal 

 culated at this moment. Supposing 

 the ship to be at the D.R. position, 

 the altitude of the heavenly body 

 observed can be calculated trigono- 

 metrically, as can also the direc- 

 tion, i.e. the bearing by compass. 

 Thus three factors are known : 



(a) The observed altitude, which 

 must be correct, as the observer 

 has measured it with his sextant. 



(b) The calculated altitude which 

 is only correct provided the ship 

 is in the D.R. position, 'c) The 

 direction of the heavenly body. 

 The D.R. position is put on the 



NAVILLE 



chart and through this position 

 the direction of the heavenly body 

 is drawn. The difference between 

 the observed and calculated alti- 

 tudes is noted, and from this on 

 the chart the true position is ob- 

 tained, drawing what are known 

 as position lines. This method is 

 that commonly used by mariners. 



A. E. Buckland, R.N., D.S.O. 

 Bibliography. Wrinkles in Prac- 

 tical Navigation, S. T. S. Lecky, 

 rev. ed. 1890 ; Navigation and 

 Nautical Astronomy, F. C. Stebbing, 

 1903 ; Modern Navigation, W. Hall, 

 1909 ; Admiralty Manual of Navi- 

 gation. 



Navigation Acts. Term applied 

 to a number of enactments de- 

 signed to regulate shipping to the 

 advantage of British ships. Such 

 legislation is to be found in the 

 reigns of Richard II, Henry VII, 

 and Elizabeth, but Cromwell's 

 Navigation Act of 1651 was the 

 first comprehensive enactment. 

 This Act, directed against the very 

 profitable Dutch carrying trade, 

 refused admission into English 

 ports of all goods not carried in 

 English ships, or in the ships of 

 the country of origin, while 

 English goods could be exported 

 only in English vessels. It bene- 

 fited English shipping, but it 

 raised the price of imports and 

 caused a war with the Dutch. 

 Enactments in 1660 and 1663 for- 

 bade colonial trade to any but 

 English ships, a restriction des- 

 tined to be a great source of 

 trouble with the American colonies. 

 The Acts were completely repealed i 

 in 1849, and in 1854 even the coast- 

 wise trade was thrown open. 



Navigators' Islands. Original 

 name of the islands in the Pacific 

 Ocean now known as the Samoan 

 group (q.v.). They were so named by 

 their discoverer, Louis Antoine de 

 Bougainville, 1768. 



Naville, EDOUARD HENRI (b. 

 1844). Swiss Egyptologist. Born at 

 Geneva, June 14, 1844, he studied 

 in Geneva, 

 London, Paris, 

 and Berlin. In 

 1869 he pro- 

 ceeded to 

 Egypt, where 

 from 1883 on- 

 wards he car- 

 ried out im- 

 portant exca- 

 vations, partly 

 on behalf of 

 the Egypt Exploration Fund. They 

 included the store-city of Pithom, 

 Goshen, the city of Onias, and 

 the temple of Deir-el-Bahri. His 

 translated works include, The Old 

 Egyptian Faith, 1909 ; Archae- 

 ology of the O.T. ; Was the O.T. 

 written in Hebrew ?, 1913 ; and 

 The Text of the O.T., 1916. 



I 



E. H. Naville, 

 Swiss Egyptologist 



