Within, there is a glorious harbor great enough for a world’s armada. But the entrance is a Pass of Thermopylæ.
Commanding that pass and all approaches far out to sea with zones of fire whose intersecting circles marked rings of sure destruction, were defenses honestly built. They were ready to receive and withstand that climax of destructiveness which man’s science has embodied in the conical steel projectile fired from the rifled gun.[91]
The navy that invested the harbor entertained no illusions on that score. It had not dared the attempt to force the passages of Narragansett. It would not dare to force the passages of Boston. As at Narragansett, its business was to occupy the defenders and wear them out while the army fell on them and on Boston from the land.[92]
[Illustration: MAP ILLUSTRATING THE ENEMY ATTACK ON BOSTON AND NEIGHBORING CITIES]
The ships entered a shrouded, black sea where there was not a light to warn of reef or shoal. Lightless themselves, they groped with deep-sea leads and sounding machines till they assured themselves of safe positions where they might have sea-room to swing around in great closed circles at high speed.
These circles would cut deeply into the circles of the fire zones of the defenses. At close range the vessels, invisible to the forts, could send a furious volley into them, and rush past before the guns could find them, to return on their circle and fire from some other point. It was the penalty that darkness lays on land defenses. But it penalized the ships, also.[93]
They would have to fire without sighting their mark. They dared not betray themselves to the waiting guns on land by throwing their search-lights on the defenses, while the defenses could sweep the sea incessantly, for their searchlights were disposed along miles of coast, far aloof from the batteries.
If the search-lights were effective, the ships should have to flee to the farthest limit of the coast guns’ range. At that distance they, in turn, could not deliver an effective bombardment of the land so long as it was dark. So, then, all the ferocious game of war centered for the time on the search-lights. The death-laden ships, the death-laden guns on land, had to wait till it was learned what the lights would do.[94]