ous reefs of rocks encroaching on the channel and the violent currents to which they give rise, making navigation extremely hazardous for all kinds of vessels.
A clear idea of the nature of these obstructions and dangers in the original condition of the strait is given in the report of Lieutenant Commanding Davis, who, with Lieutenant-Commanding David Porter, made a survey of the place in 1848. "The strength of the current," he says, "is such that sailing-vessels can only stem its force or escape from it by a commanding breeze; but, as the main course of the flood-tide keeps the middle of the Eastern Channel, it is most secure for vessels which are coming from the westward with the tide to place themselves in the middle of the stream and follow its direction. This plan, however, is inadvisable for any but small vessels, on account of the rocks, the Pot and Frying-Pan, which lie in or very near the mid-channel, are in the way both going to the eastward and westward, and have but little water on them at low tide. There is also a reef called Way's Reef, which lies in the course followed by steamboats principally when coming from the eastward against a strong flood. It is their custom to keep close round Pot Cove, and run up under Hallet's Point, by which they avoid the strength of the flood. In this part they find an eddy-current in their favor. But on the ebb the greatest danger arises from the divergence of the current, when the ebb branches off into three directions to take the course of the three channels—the main Ship-Channel, the Middle Channel, and the Eastern Channel. The safe navigation depends here upon deciding sufficiently soon at the point of separation which channel shall be taken; and the neglect to do this, or a loss of control over the vessel for any reason, frequently results in being carried on the Gridiron. When a vessel that has attempted the Eastern Channel finds herself carried toward the Gridiron, her only chance for safety is to run for the Middle Channel, which is narrow and made precarious by the middle reef, the outer rock of which is the Negro Head. The Gridiron is, owing to the strong set of the tide upon it, the most dangerous reef in the passage. The reef known as Bread and Cheese, on the eastern end of Blackwell's Island, is also very dangerous. Vessels are liable to go on it in the flood, when it is covered, by getting into the eddy near it with a light wind. The chief danger is on the ebb, and from the same reason that makes the Gridiron dangerous—i. e., the strong set of the tide in that direction."
The reefs (see map) known as the Gridiron, Flood Rock, Hen and Chickens, and Negro Head, are all essentially parts of one reef, which is designated as the Middle Reef. Between this reef and the reef which is marked by the projections of the Great and Little Mill Rocks, is situated the Middle Channel. The Eastern Channel is included between the Middle Reef and Hallet's Point. The South or Main Ship Channel lies to the west of Great and Little Mill Rocks, and between
