May 5, 1899.] 



SCIENCE. 



641 



as much by causing ships to go fewer miles 

 as by causing them to go faster. 



This generation is familiar with the part 

 that has been played by steam propulsion 

 in increasing the speed of ships, but, besides 

 the increase in the rate of travel, modern 

 motive power, by making possible a depar- 

 ture from the old meteorological routes, has 

 had another and a greater effect in the 

 progress of the universal policy of civilized 

 nations to accelerate transit from place to 

 place to the utmost possible extent. When 

 the wind was the sole motor of ocean-going 

 vessels the best economy was realized by 

 passing through regions of favorable meteor- 

 ological conditions without reference to 

 the directness of the route. Thus, in sail- 

 ing from Europe to the United States, it 

 was customary to pass southward along 

 the eastern shores of the Atlantic to the 

 Cape Verde Islands, and thence westward 

 through the trade-wind region along the 

 route followed by Columbus on his first 

 voj'age to the New World, and finally 

 northward into the region of prevailing 

 westerly winds and along the western 

 shores of the Atlantic to the point of desti- 

 nation. In making this voyage, ships trav- 

 ersed 4,400 miles in passing between ports 

 that were only 2,400 miles apart on the 

 surface of the earth . 



Under steam, even if they go no faster, 

 ships may yet get farther toward the port 

 of destination in a given time because the 

 winds and currents may be disregarded, 

 and they may be navigated over the oceans 

 along great circles of the earth. 



The increasing recognition among mari- 

 ners of the sound principle of conducting a 

 ship along the arc of the great circle joining 

 the points of departure and destination and 

 the expanding sense of the advantages to 

 be gained by a knowledge of this branch of 

 nautical science have greatly heightened 

 the value of methods which place the bene- 

 fits of the knowledge and use of the great- 



circle track at the service of the mari- 

 ner without the labor of the calculations 

 which are necessary to find the series of 

 courses to be steered. Inasmuch as great- 

 circle courses alter continuously in proceed- 

 ing along the track, it becomes necessary to 

 know the latitude and longitude of the ship 

 in order to determine the course to be fol- 

 lowed. At the present day there are con- 

 venient means for determining at sea the 

 longitude as well as the latitude, but before 

 the early part of the present century these 

 means did not exist, and great-circle sail- 

 ing was impracticable. The general lack 

 of the application of the principles of the 

 great circle in later times, and even in the 

 present generation, seems to have resulted 

 not from the want of recognizing that the 

 shortest distance between any two places 

 on the earth's surface is the distance along 

 the arc of the great circle passing between 

 them, nor that the great-circle course is the 

 only true course and that the courses in 

 Mercator and parallel sailing are circuitous, 

 nor yet to a due appreciation of the advan- 

 tages to be gained by a knowledge of the 

 great-circle course as a means for obtaining 

 the most advantageous track in windward 

 sailing; but to the tedious operations which 

 have been necessary, and to the want of 

 concise methods for rendering these benefits 

 readily available. 



The solution, every time the course must 

 be determined, of a spherical triangle in 

 which the two sides and the included angle 

 are given is a formidable operation for a 

 mariner as compared with the measure- 

 ment on a compass diagram of the direction 

 of the straight line representing the circuit- 

 ous path of the ship's track on the Merca- 

 tor chart. At page 662 of the ninth edition 

 of a work on Practical Navigation by Cap- 

 tain Lecky, of the Royal Naval Reserve of 

 Great Britain, there is a section entitled 

 ' Great Circle Courses found from Bur- 

 wood's Tables,' which has doubtless been 



