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Mr GODFRAY, ON A CHART AND DIAGRAM 



3. There are other cases where the adoption of the great-circle course would have ad- 

 vantages independent of the diminished distance. Suppose in the previous example that the 

 wind instead of being right ahead of the Mercator's course is 6^ points to the south of it, so 



C. Clear 



that the two vessels may adopt their respective courses, the second being close hauled and the 

 other 1^ points more away : then assuming their sailing qualities to be the same under similar 

 circumstances, that which is close hauled will not make so much head-way as the other, and at 

 the end of the day the Mercator's distance will have been diminished by 120 miles, the other 

 by pi'obably 130 or more — thus adding 10 miles to the original difference of 24. 



4. It may sometimes happen that an island or a group of islands lies precisely in the 

 ship's track as found by Mercator, and the sailor, obliged to deviate from it, will, without doubt, 

 supposing all other circumstances equally favourable, choose that direction which seems to 

 separate him less from the original track, and by so doing often take a longer route when one 

 considerably shorter is open to him ; and it is also important to remark, that not only is every 

 course which lies between the Rhumb track and the great-circle shorter than the former, but 

 that he may go to an equal distance on the other side of the great-circle and still have 

 distances shorter than the Rhumb. 



For instance : suppose a ship bound from New York to Gibraltar. It will be found by 

 reference to Mercator's chart that the Rhumb track passes through the group of the Azores 

 a little to the north of Santa Maria, the southernmost island. Supposing then that the 

 ship-master guided by this chart wished to give the islands a wide berth, he would sail to the 

 southward of Santa Maria and thus leave the whole group to the northward. But if we trace 

 the track from New York to Gibraltar on the great-circle chart, we find that it passes some 

 180 miles to the north of the most northerly of the whole group and about 270 miles north of 



