 The chief reason is that Caesar, having found he could not set sail from the small harbour of Boulogne with even eighty ships simultaneously, decided that he must take another point for the sailing of the more than 800 ships of the second expedition.Holmes argues that, allowing for change in the foreshore since Caesar's time, 800 specially built ships could have been hauled above the highest spring-tide level, and afterwards launched simultaneously at Wissant, which would therefore have been "commodissimus" or opposed to "brevissimus traiectus".In fact the logical place to assemble 800 or so ships was in the large lagoon (where now there is farmland and a maze of drainage ditches) behind a coastal fringe of islands (where the modern ports of Calais and Dunkirk now sit) because in Caesar's day an estuary stretched all the way inland to the site of the modern town Saint-Omer.