434 THE POPULAR SCIENCE MONTHLY. 



ous reefs of rocks encroaching on the channel and the violent currenis 

 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 Por- 

 ter, made a survey of the place in 1848. " The strength of the cur- 

 rent," 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 direc- 

 tion. 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 

 sufiiciently 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 mid- 

 dle 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 be- 

 tween 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 



