CHAP. XVI.] 



SUMNER'S METHOD 



371 



positions — to a certain extent, that is, for it must be remem- 

 bered that as the intersection of our Knes is governed by the 

 run allowed, a current, or constant error in calculating the run, 

 might give an apparently good position which may really bo 



C/ 



pi'3 



'n/* 



Fig-, 72. 



considerably in error, even when the third intersection is 

 obtained, with certain arrangements of the lines and the run. 

 Sumner's method is, in fact, the means by which all indi- 

 vidual observations can be combined, and is from every point of 

 view invaluable. 



NEW NAVIGATION. 



The method of. obtaining positions known by the name of 

 " New Navigation " is particularly applicable when the bearing 

 of the heavenly body lies between 20° and 70° from the meri- 

 dian. It gives a shorter line of position, thus coinciding more 

 accurately with the arc of a circle of equal altitude, than a line of 

 position drawn from a point found by the chronometer method. 



" New Navigation " is now becoming so well known that it 

 will be sufficient to mention that it consists in assuming a 

 latitude and longitude, and in calculating a correction to this 

 assumed position. A line of position can then be drawn through 

 the true position thus obtained, and its results combined with 



24—2 



