TRANSACTIONS OF SECTION E. 



707 



two hundred years later, had not yet been able to emancipate himself from the 

 overpowering authority of Ptolemy. And in this he did not sin alone,for Italian and 

 other cartographers of a much later time still clung pertinaciously to the same 

 error. 



There were others, however, who recognised the value of these charts, and 

 embodied them in maps of the entire world. Among such were Marino Sanute 

 (1320) and Fra Mauro (1453), both of whom made their maps the repository of 

 much information gathered from the Arabs or from their own countrymen who 

 had seen foreign parts. Fra Mauro, more especially, has transmitted to us a 

 picture of Abyssinia marvellously correct in its details, though grossly exaggerated 

 in its dimensions. 



Another step in the right direction was taken when the cartographers and 

 pilots of Portugal and Spain returned to the crude projection of Dicaeareh, 

 Eratosthenes, and Marinus, which enabled them to lay down places according to 

 latitude and longitude upon their ' plane charts.' 



Gerniany, debarred from taking a share in the great maritime discoveries of the 

 age, indirectly contributed to their success by improvements in mathematical 



^^^-j CATALAN MAP. 



geography and the introduction of superior instruments. The navigators of the 

 early middle ages still made use of an astrolabe when they desired to determine a 

 latitude, but this instrument, which in the hands of an expert observer furnished 

 excellent results on land, was of little use to a pilot stationed on the unsteady deck 

 of a vessel. Regiomontanus consequently conferred an immense service upon the 

 mariners of his time when, in 1471, he adapted to their use an instrument 

 already known to the ordinary surveyors. It was this cross staff which Martin 

 Behaim introduced into the Portuguese navy, and which quickly made its way 

 among the navigators of all countries. Most observations at sea were made with 

 this simple instrument, variously modified in the course of ages,-until it was super- 

 seded by Hadley's sextant. In the hand.s of the more skilful navigators of the 

 seventeenth century, such as Baffin, James, and Tasman, the results obtained vrith 

 the cross-staff were correct within two or three minutes. 



Far greater difficulties were experienced in the observations of longitudes. 

 Lunar eclipses were most generally made use of, but neither the Ephemerides of. 



z z 2 



