INTRODUCTORY 5 



by the celebrated map usually attributed to the Alexandrian 

 astronomer and geographer, C. Ptolemy, in the second 

 century a.d., one of the notable features of which is that 

 it represents the Indian Ocean as an enclosed sea bounded 

 to the south by land extending from Africa to China — an 

 error which remained uncorrected till the time of Captain 

 James Cook, towards the end of the eighteenth century. 

 (Plate I.) 



Ptolem}^, like others before him, believed that the furthest 

 known land to the east (Asia) came so near to the known 

 west coast of Europe that a ship might easily sail from 

 Spain to India, and there can be no doubt that this error 

 which Ptolemy's map did so much to perpetuate had great 

 weight in determining the voyages of Columbus and others 

 towards the end of the fifteenth century, and so led eventually 

 to the discovery of America. With Ptolemy we come to 

 the end of the scientific oceanographers of classical times. 



Let us now pass over the dark ages and some succeeding 

 centuries during which the scientific investigation of nature 

 was at a standstill. With the exception of the explorations 

 of the Norsemen in the North Atlantic and of the Arabs in 

 the Indian Ocean, in mediaeval times, when it is said they 

 obtained the idea of the mariner's compass from China, little 

 advance was made till the glorious period at the end of the 

 fifteenth and the beginning of the sixteenth century, when the 

 Portuguese and Spaniards opened up enormous new areas of 

 ocean and demonstrated that the Earth is a sphere. 



Prince Henry of Portugal, surnamed " The Navigator " 

 (grandson of " Old John of Gaunt"), founded in 1420 his 

 school of maritime research at Sagres, near Cape St. Vincent, 

 on the south-west corner of Portugal, where he trained the 

 men who led successive voyages of exploration in the Atlantic. 

 At the time of his death, in 1460, the west coast of Africa was 

 known down to about a third of the way to the Cape of Good 

 Hope. The Cape was finally rounded by Bartholomew Diaz 

 in 1486, but it was not till 1497 that Vasco da Gama com- 



