GEOGRAPHICAL INSTRUMENTS AND 

 MAPS. 



I. INSTRUMENTS USED FOR GEOGRAPHICAL PURPOSES. 



THE dawn of modern geography broke upon the world when 

 Prince Henry of Portugal began to send forth his expeditions 

 along the coast of Africa ; and it was the needs of the daring 

 seamen of that age which caused the demand for geographical 

 apparatus to be met. The first geographical (as distinguished 

 from astronomical) instruments were those for ascertaining the 

 position and course of a ship ; they were used by the discoverers 

 of the fifteenth and sixteenth centuries, and the results consisted 

 in the delineation of new coast-lines, and of their most prominent 

 features. 



The compass and the rough sea card were the only appli- 

 ances until the learned Nuremburger, Martin Behaim, invented 

 the application of the astrolabe to purposes of navigation, which 

 enabled mariners to ascertain their latitude. This was in the 

 year 1480. The astrolabe was used by Vasco da Gama on his 

 first voyage round the Cape of Good Hope ; but the movement 

 of a ship rendered accuracy impossible, and the liability to error 

 was increased by the necessity for three observers. One held 

 the astrolabe by a ring passed over his thumb, the second measured 

 the altitude, and the third read off. Some years afterwards the 

 cross-staff was invented to take the altitude of the sun or of a 



