THE TIDES. 151 



the tides. At a much later time than that, we hear 

 from the ancient Greek writers and explorers 

 Posidonius, Strabo, and others that in certain 

 remote parts of the world, in Thule, in Britain, in 

 Gaul, and on the distant coasts of Spain, there 

 were motions of the sea a rising and falling of the 

 water which depended in some way on the moon. 

 Julius Caesar came to know something about it ; but 

 it is certain the Roman Admiralty did not supply 

 Julius Caesar's captains with tide tables when he 

 sailed from the Mediterranean with his expedition- 

 ary force, destined to put down anarchy in Britain. 

 He says, referring to the fourth day after his first 

 landing in Britain " That night it happened to be 

 full moon, which time is accustomed to give the 

 greatest risings of water in the ocean, though our 

 people did not know it." It has been supposed 

 however that some of his people did know it some 

 of his quartermasters had been in England before 

 and did know but that the discipline in the 

 Roman navy was so good that they had no right 

 to obtrude their knowledge ; and so, although a 

 storm was raging at the time, he was not told that 



