98 : The Atlantic 



around Africa was that he preferred to beHeve that no human Hfe 

 could survive a passage through the tropics. Nonetheless, Herodotus 

 added considerably to our knowledge of the Atlantic Ocean. Tidal 

 movement in the Mediterranean is so slight as to have escaped the 

 attention of most of the classic writers, and Herodotus is the first to 

 give us an account of tidal action in the Indian Ocean and in the 

 Atlantic. 



Pythias, who lived in Massilia, the present French city of Marseille, 

 in the closing years of the fourth century b.c. was not only one of the 

 greatest of classic scholars, but also one of the greatest explorers of 

 the ancient world. Somewhere between 325 b.c. and 310 b.c. he pro- 

 jected a voyage in Atlantic waters. Since his voyage was to be a long 

 one, he felt that he needed to know all that he could about the earth 

 and the heavens. Like many of the learned Greeks of his time he ap- 

 preciated that the earth was not flat, but a sphere. He established two 

 reference points to guide him on his travels — that is, he ascertained 

 the position of the polar star and he made an observation of the ex- 

 act latitude of his own city, the port from which he was departing 

 on his travels. At the time of the solstice he erected a perpendicular 

 pointer which, for purposes of measurements, was divided into 120 

 parts. Then he measured the shadow of the sun at high noon which 

 turned out to be 41 and "^ths parts. Converted into degrees of arc 

 this would give a reading of 70° 47' 50''. In common with Eratos- 

 thenes and Hipparchus he knew about the inclination of the ecliptic 

 23° 51' \^" . Subtracting this from the altitude of the sun he obtained 

 46° 56' 35''. To obtain his latitude he would therefore subtract 

 this from 90° which gave him a reading of 43° 3' 25''. He 

 then had to make a correction for half of the diameter of the sun; 

 this could be considered roughly as 16' which would be added to his 

 reading to give a latitude of 43° 19' 25'' — roughly the present latitude 

 of the observatory at the port of Marseille. Among his other scientific 

 accomplishments Pythias reported observation of the tides of the 

 Atlantic made during his long voyage and attributed them to the 

 moon. 



In the previous chapter we have already referred to Pythias' voy- 

 age to England because it throws light on the extent of ocean navi- 

 gation in the North Atlantic before his time. Pythias provides an ac- 

 count of his trip around the British Isles and shows that he knew 

 also about Ireland. It is now believed that he sailed also to Iceland 

 and traveled far enough beyond Iceland to come in contact with the 

 drifting ice pack. The name he used for Iceland was Thule. 



