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ROYAL SOCIETY OF CANADA 



that part of liis book which may he called scientific, for it is in connec- 

 tion with a windrose and contains practical instrnctions for navigation, 

 to tlie effect that in sailing on a direct northern course until the pole 

 star is elevated one degree, "that degree is equal to seventeen leagues 

 "Hnd a half and that is the distance you will have gone." There is no 

 uncertainty about that statement ; but Varnhagen and other advocates 

 of "fancy lejigues," in order to get leagues to suit their theories, started 

 an id«i that latitudinal and longitudinal degrees on a great circle of the 

 er.rth were of different length. P^nciso disposes of that idea. His 

 sjiiling directions continue tlius : "Also, if your course is one point the 

 " distance sailed will be 17 ^J4 leagues and departure 3 ^[j leagues for the 

 "'degree. If your course be two points, count tlic distance sailed 19 ^|g 



\7'A 



LEAGUKS OF DEPARTUKi: 



FniUKK 1. 



" leagues and departure 7 % leagues. If three points count the distance 

 "sailed as 21 ^jg leagues and the departure 11 '^|o leagues. If the course 

 "be four points count the distance as 24:% leagues and the departure 

 " 17 % leagues." The above diagram (Fig. 1) will show the mean- 

 ing graphically . 



