LENGTH OF A DEGREE 13 



The Method Employed by Columbus 



In the first place, it should be recalled that Eratos- 

 thenes^^ had measured the length of a degree. In 

 order to do this he had determined astronomically 

 the latitude of tvvo places (Syene, in Upper Egypt, 

 and Alexandria), supposed to be on the same merid- 

 ian. The distance between these two points (5000 

 stadia) was measured ; and with these data the value 

 of a degree was determined by a simple operation in 

 arithmetic. The astronomers of the Caliph Al-Ma- 

 mun proceeded in an exactly similar way. They de- 

 termined, by astronomical observ^ations, the latitude 

 of a given point. They then tra\'eled along the 

 meridian of that point for a measured distance. A 

 second observation was taken; and from these data 

 the value of 56 >^ miles for a degree was obtained. ^^ 



The significant matter, for this discussion, in the 

 two cases mentioned is that the original method of 

 measuring a degree was to determine astronomically 

 the position of two points on the same meridian, 

 measure the actual distance between them, and cal- 

 culate the length of a degree by arithmetical compu- 

 tation. The contention of the present study is that 

 Columbus followed this procedure in his verification 



16 E. H. Bunbury: A History of Ancient Geography, 2 vols., London, 

 1879; reference in Vol. i, p. 621. 



17 The accounts of this famous survey are not altogether clear. Ap- 

 parently several surveys were made, and the values 56, 56 }i, 57, and 

 57 H were obtained — 56 H being the figure more commonly accepted 

 (Geographie d'Aboulfeda, Vol. 2, Part I, p. 17; Joachim Lelewel: Geo- 

 graphic du Moyen Age, 4 vols., Epilogue, and atlas, Brussels, 1850-57; 

 reference in Vol. i, pp. xxii-xxiv. 



