Wind-charts into Passage-charts. 349 



could be used over again. An extract from the foregoing Table 

 will suffice for an example of what is meant ; where, in order to 

 save space, the figures that refer to the eight principal points of 

 the compass are alone inserted. 















H". 



N.E. 



E. 



S.E 



■I* 



s.w.w 



|n.W. 





K". Hours 6 | Force mod. | 14 24 51 57 45 57 



51 



24 



L4 



24 



51 



57 



45 



57 



51 



21 







N.E. 1 Hours 17 1 Force mod. 1 40 68 144 161 127 



161 



144 



68 



40 



6S 



141 161 



127 161 



144 68 1 



E. .. 



Hours 3 1 Force mod 1 7 12 25 28 



22 



28 



25 



12 



7 



12 



25 



28 



22 



28 25 



12 







Si ... 

 s 



. 1 Hours 2 [ Force mod. 1 5 8 17 



19 



15 



L9 



17 



8 



5 



8 



17 



19 



15 19 



17 8J 





Hours 6 I Force mod. 1 14 24 



51 



57 



45 



57 



-31 



24 



14 



24 



51 



57 4c 



57 51 24 1 





s.w 



. J Hours 6 Force mod. 14 



24 



51 



57 



45 



57 



51 



24 



14 



21 



51 51 



45 57 51 24 





w 





Hours 3 Force mod. 



7 



12 



25 



23 



22 



28 



25 



12 



7 



12 2i 



> 28 22 28 25 12 1 







KW 



Hours 4 Force mod. 





9 



16 



34 



38 



30 



38 



34 



16 



9 It 



34 38 30 38 3.1 lfi 















Total. 



If the slips were of sufficient length to include the data for 

 every class of ship, a single operation would simultaneously 

 build up Tables for all. 



A navigator wishing to find the probable duration of his in- 

 tended voyage, would refer to a chart on which the results of 

 these calculations had been protracted in the form of diagrams. 

 He must set his compasses to the radius of the diagram nearest 

 to the commencement of his intended route, measuring it in a 

 direction parallel to the route. He will thereby obtain a scale 

 of probable distance for one hour's sail during that part of his 

 voyage, and he will prick out his passage accordingly. When he 

 has come within the range of another diagram he will set his 

 compasses afresh. Continuing on this principle, he will dot out 

 the probable duration of the whole of a proposed passage in the 

 simplest possible manner. He will thus be able to select the 

 quickest out of any number of routes that may be suggested to 

 him, and to determine, on the most trustworthy of existing data, 

 what is the best course to adopt in sailing from any one part of 

 the ocean to another. 



The method of altering a diagram so as to include the effect 

 of a current, is too simple to require explanation. 



