CHAP. XIX.] SWINGING SHIP 421 



The readiest way of examining the results of our observations 

 is by use of the Graphic method (Fig. 87). 



Drawing a long line, measure off equal parjjs along it, for 

 the points of ship's head, and at each point on this normal 

 lay off, at right angles, a line equal to the degrees and minutes 

 of the deviation, on any scale we choose — easterly deviation 

 to the right, westerly to the left of the normal. 



Lines drawn through the extremities of these abscissae will 

 denote the curve of deviation observed. 



By the irregularities of this curve, we can judge of the 

 correctness of the observations very fairly ; and for our final 

 table of deviation, we can draw a mean curve, if there are 

 many irregularities, and measure to that for the amount of 

 deviation for each point. 



The valuable results for variation obtainable from swinging 

 have already been mentioned at p. 361. 



