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The Locks on the Chesapeake and Ohio Canal, located in Maryland, West Virginia, and Washington, D.C. of the United States, were numbered from 1 to 75 with two locks, 63⅓ and 64⅔, having fractional numbers and no lock 65. There is also a lock at the downstream end of the canal in Washington, DC where Rock Creek flows into the Potomac River which is sometimes called Lock 0 or the Tidewater Lock. The canal had several kinds of locks: Lift locks, River locks, and Guard locks (also called Inlet locks). The final locks (70-75) had been completed earlier than 1842, before locks 62 and 66.〔 p.20〕 It was found that the level of the canal between locks 62 and 66 could be raised in three steps instead of four. So the additional locks through there were numbered 1⅓ steps apart (62, 63⅓, 64⅔ and 66) so that the other locks, already completed, did not have to be renumbered. While the "Frequently Asked Questions" website published by the National Park Service states that it takes about 10 minutes for a boat to lock through,〔(Frequently Asked Questions ), National Park Service〕 experiments done in the 1830s show that it was possible for a boat to go through in 2½ minutes, although 3 minutes was their average. In 1897 it was shown that steamboats took 5 to 7 minutes to lock through whether going upstream or downstream (respectively).〔http://candocanal.org/histdocs/Double_Boat_Report.pdf〕 ==Guard locks== Since these were locks to regulate water coming into the canal, they are frequently called inlet locks. At the slackwaters (particularly at Big Slackwater and Little Slackwater) they allowed boats to reenter the canal from the slackwater. There is no guard lock #7, since Dam #7 was proposed to be around mile 164 near the mouth of South Branch, but it was never built. A steam pump was later put where this dam would have been in 1856.〔Unrau p. 208 footnote, 470〕 In 1872, a new steam pump was put 10 miles upstream at mile 174.2, and gave about 24 cubic feet per second of water.〔 p. 215〕 The first guard lock was made of structures from George Washington's Potomac Company Little Falls skirting canal, and were repurposed for the C&O.〔Unrau p. 238〕 The second guard lock at Violette's lock, was confusingly numbered Lock 24 for a period of time when that was the end of the canal. Later, when the section up to Dam #3 (Harpers Ferry) was opened, Lock 24 was the lock at the Seneca Aqueduct (i.e. Riley's Lock). Guard lock #2 is also 88' 5" long, making it too small for a standard C & O canal boat (92') to go through.〔Hahn, Towpath Guide, p. 51〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Locks on the Chesapeake and Ohio Canal」の詳細全文を読む スポンサード リンク
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