The last factor was the fortress itself. This so-called 'Gibraltar of the West,' this 'Quebec by the sea,' this 'Dunkirk of New France,' was certainly first of its kind. But it was first only in a class of one; while the class itself was far from being a first among classes. The natural position was vastly inferior to that of Quebec or Gibraltar; while the fortifications were not to be compared with those of Dunkirk, which, in one sense, they were meant to replace. Dunkirk had been sold by Charles II to Louis XIV, who made it a formidable naval base commanding the straits of Dover. When the Treaty of Utrecht compelled its demolition, the French tried to redress the balance a little by building similar works in America on a very much smaller scale, with a much more purely defensive purpose, and as an altogether subsidiary undertaking. Dunkirk was 'a pistol held at England's head' because it was an integral part of France, which was the greatest military country in the world and second to England alone on the sea. Louisbourg was no American Dunkirk because it was much weaker in itself, because it was more purely defensive, because the odds of population and general resources as between the two colonies were fifteen to one in favour of the British, and because the preponderance of British sea-power was even greater in America than it was in Europe. The harbour of Louisbourg ran about two miles north-east and south-west, with a clear average width of half a mile. The two little peninsulas on either side of the entrance were nearly a mile apart. But the actual fairway of the entrance was narrowed to little more than a clear quarter of a mile by the reefs and islands running out from the south-western peninsula, on which the fortress stood. This low, nubbly tongue of land was roughly triangular. It measured about three-quarters of a mile on its longest side, facing the harbour, over half a mile on the land side, facing the enemy's army, and a good deal under half a mile on the side facing the sea. It had little to fear from naval bombardment so long as the enemy's fleet remained outside, because fogs and storms made it a very dangerous lee shore, and because, then as now, ships would not pit themselves against forts unless there was no rival fleet to fight, and unless other circumstances were unusually propitious.