FOR FACILITATING GREAT-CIRCLE SAILING. 277 



Santa Maria; and therefore, from the remark in the previous paragraph, the ship might go 270 

 miles still further north and not make its route longer than that which would probably be 

 chosen, 



I am aware that the example I have selected is not a very good one, for the winds which 

 prevail during the greater part of the year, and the presence of the Gulf-stream, may induce a 

 ship-master to pass to the northward, and thus unconsciously approach the shortest track unless 

 the vessel be a steamer, which probably would be kept on the southward course. However, 

 this will serve to illustrate what may occur in similar cases in those parts of the world where 

 the winds and currents would not influence the choice of the vessel's route. 



I need not dwell any longer on the practical value of Great-circle sailing to the seaman. 

 In distant voyages, as to Australia or New Zealand, its use will abridge the distance by 

 several hundred miles, more than 1000 in some cases, and in shorter journeys where the gain 

 in distance is small, the gain in time may, as we have seen, be considerable. 



In the particular case of the voyage to Australia, there is another advantage which may 

 possibly occur also elsewhere : — when the trade-winds in the Southern Atlantic have been 

 cleared, if the course be shaped by Mercator, the ship will have to run through a region where 

 storms are frequent, almost permanent ; but if a great-circle course be adopted, or rather what 

 has been called a composite course, which will be presently explained, a higher southern 

 latitude is reached where the wind is usually favourable, storms of rare occurrence — and the 

 distance perhaps 1000 miles shorter. 



It is very possible to find routes where the great-circle course would be the stormy one 

 and Mercator's free, and there are frequent cases too in which even Mercator's track is 

 abandoned for) a longer one, to take advantage of well-known ocean currents or prevalent winds 

 such as the Trades. It is not to be expected, nor indeed to be desired, that Great-circle sailing 

 should supersede the methods now in use, but it is very desirable that it should form a part of 

 the sailor's nautical knowledge, not necessarily for him to adopt in all cases, but that he may 

 know which is the shortest route, that he may see it on his chart, and that he may be able to 

 follow it if his judgment tells him it is both practicable and preferable. 



Composite Sailing. 



There is yet another and a very simple case of Great-circle sailing, or rather a modification 

 of it, to which reference was made just now. It is called composite sailing, and presents itself 

 whenever the great-circle track reaches too high a latitude where the ice renders it dangerous 

 or impossible for the ship to penetrate. In that case some one parallel of latitude is fixed 

 upon for the maximum ; and the shortest route, under these conditions, will consist of a 

 portion of that parallel and of the portions of two great circles which are tangents to it, and 

 pass one through the ship, the other through the destination. On the great circle chart the 

 track will be the two straight lines drawn from the two places so as to touch the circle of 

 highest latitude, and the part of this circle between the points of contact. This combination 

 of great-circle sailing and parallel sailing offers therefore no difficulty. If the ship is driven 

 into a higher latitude than that which was intended it must be left to the ship-master's own 



