82 Master Minds of Modern Science 



before every ship's captain out of sight of land was to 

 know where he was. Latitude — that was easy enough, 

 for it could be found by observation of the sun at midday 

 or of the Pole Star at night ; but longitude was a very 

 different matter. You will remember that Christopher 

 Columbus started across the Atlantic, not in the hope of 

 discovering America, of which he knew nothing, but with 

 the idea of finding a new route to India, for one thing 

 he did know was that the earth was round. After many 

 days he sighted the Bahama Islands, which are actually 

 in sixty-six degrees west longitude, but he was so hope- 

 lessly out in his calculations that he believed he was 

 among islands in the China Seas, two hundred and thirty 

 degrees west from Spain. 



And such blunders were made for a very long time after 

 Columbus. In the eighteenth century Commodore Anson 

 wanted to make the island of Juan Fernandez in order to 

 get fresh water and fruit for his crew, who were dying of 

 that terrible disease scurvy. He got into its latitude 

 easily enough, and sailed eastward, though as a matter 

 of fact he was already east of the island. In consequence 

 the first land he sighted was the mainland of South 

 America, and he had to turn round and sail westward for 

 days, losing many poor fellows whose lives might other- 

 wise have been saved. 



To go back to the time of Columbus, the discovery of 

 America caused such a rush of adventurous voyagers in 

 that direction that the need for some means of finding 

 their longitude became most pressing. Clever men all 

 over the world tackled the problem, and in 1598 Philip III 

 of Spain offered the huge prize of one hundred thousand 

 crowns to anyone who could solve it, while the Dutch 

 followed with an offer of thirty thousand florins. 



The only man who came anywhere near a solution was 

 the great Galileo. With his telescope he observed how the 

 moons of Jupiter pass behind the planet, and he suggested 



