GEOGEAPHICAL LATITUDE. 



By Walter B. vScaife, Pji. 1). (Vieuua). 



Introduction. — The designation of the situatiou of places ou the sur- 

 face of the earth by their hititude and longitude is such a common oc- 

 currence that one rarely stops to ask how these quantities are deter- 

 mined, much less to consider the evolution of the ideas which form the 

 basis of the usage, or to study the slow progress of events through 

 which (even after the theory was perfected) accuracy of observation and 

 measurement was first n)ade possible, while new and improved meth- 

 ods were being invented tor representing the results thereof. Though 

 latitude and longitude are so iutimately connected in usage and thought, 

 the methods of determining them are different, and each has its own 

 j)eculiar historical development. Hence they can be separately treated 

 without injury' to the whole subject; aud this article accordingly is 

 confined to the consideration of the historical evolution of geographical 

 latitude alone. 



The word latitude, signifying breadth, was adopted by the early geog- 

 raphers to designate situation to the north or south, in contradistinc- 

 tion to east and west, because the then known world was longer from 

 east to west, which was hence called the length, than from north to 

 south, which was then naturally styled the breadth. ^ The fact that 

 the earth is spherical and so can have, accurately speaking, no length or 

 breadth, has not altered the nomenclature adopted in the infancy of the 

 science. The technical meaning of the word latitude now includes how- 

 ever much U)ore than the crude idea of mere distance north or south of a 

 given point. It takes for granted the spliericity of the earth and its 

 division by imaginary lines running east and west, whose distances from 

 each other, thougli not exactly e<iual, n)ark the intersection with the 

 earth's surface of i)liunl) lines forming equal angles, each one to the 

 uext.^ 



The verj' fact of thinking of the earth as a whole shows that an in- 

 dividual or a people has made considerable progress in civilization, for 



' Ptolemaius, Geograpbica, lib. i, cap. vi. Tbe origin of tbe idea is ascribed to 

 Democritus of Abderos. (D'Avezac, Coup d'oeil, 2HG, note 10; Lelewcl, i, vi.) 



'-' Wben we speak of tbe latitude of a place, theu, we mean in reality not its dis- 

 tance from tb<! equator, measured on tbe eartb's surface, but the i^iigle which a plumb 

 hue at that place forms with the plane of the equator, 



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