26 COXCEPTIOXS OF COLUMBUS 



third and fourth series were first appearing. It is 

 in the light of this last fact that Columbus' state- 

 ment VI (p. 9) should be regarded: "Note that the 

 latitude of the climates which you will see here agrees 

 in all the writers; each degree corresponds to 56^ 

 miles. And this is a fact, and whatever anyone says 

 to the contrary is only words." The new obser\'a- 

 tions taken about the time, or soon after the time, 

 that Columbus made his last voyage to Guinea were 

 destroying the basis of his calculation of the length 

 of a degree. Columbus had no faith in the new^ ob- 

 servations; this would not probably have been the 

 case had he been in Guinea to make them himself. 

 Therefore it would appear that Columbus formu- 

 lated his basic concepts before he left Portugal and 

 not after his discovery of America. 



In vindication of Columbus in thus accepting an 

 erroneous estimate, it should be remembered that 

 even an approximately correct value for the length 

 of a degree was not available until the determination 

 made by Jean Picard in 1669-1670.^^ A few years 

 before this date, Newton, working on the problem of 

 gravitation, had employed a value of approximately 

 60 statute miles, instead of 6g-\-, thus underestimat- 

 ing the size of the earth nearly one-se\'enth as com- 

 pared with the underestimate of one-fourth by Co- 

 lumbus. 



■■*« [Louis] Vivien de Saint-Martin: Histoire de la geographic et des 

 decouvertes geographiques depuis les temps Ics plus recules jusqu'a nos 

 jours, text and atlas. Paris. 1873-74; reference in text, pp. 417-419. 



