Geographical Mays and Sailing Charts. 



359 



large that short portions of great circles differ but little from 

 straight lines ; hence an ordinary protractor, printed on trans- 

 parent materia], may be used. To take the departure at the 

 intersection of the great circle GO with the fifty-ninth 

 meridian, figure 26, the protractor is centered at the intersec- 

 tion, adjusted so that its 0-0 line matches the meridian, and 

 the departure is determined by where the great circle (more 



Measurement of the Angle made by the Great Circle GC with the fifty- 

 ninth Meridian by means of an ordinary protractor. 



strictly, a tangent to it at the point of departure) cuts the 

 graduation of the protractor, which, as shown in the figure, is 

 about 61J°. Continuing on the great circle, figure 25, the 

 angle of departure continually increases until at the twenty- 

 first meridian it is 90°, or due east, and at the intersection of 

 the seventh meridian, near b, figure 25, it is about 11-J south 

 of east. 



The aggregate saving of time and money would doubtless 



