How a Lock Works

How a Lock Works (HMAQ)

Location: Havre de Grace, MD 21078 Harford County
Country: United States of America

N 39° 33.363', W 76° 5.597'

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Instead of following the slope of the land, as rivers and streams do, a canal periodically takes a vertical step between long stretches of flat water. Locks were constructed at each vertical step to accomplish moving barges up and down between each of the long stretches of flat waterway. The vertical step at this lock is 12 feet. The lock's hand-operated mitre gates, while simple in concept, required close attention and experience to operate.

At the boatman approached a lock, he would sound an alarm a half to a quarter of a mile away, alerting the locktender. Entering the lock was the most demanding part of canalling. Canal boats were usually designed to fill as much of the lock as possible. Thus a boat would enter the lock with only inches to spare. If the helmsman allowed the boat to hit the lock walls, he could damage the lock walls or even sink the boat. Nevertheless, the boat had to be moving fast enough to go all the way in the lock, yet still had to be stopped before it hit the gate at the other end of the lock. Crashes of this sort were a major cause of damage to the canal, as boatmen would often race each other to get to the lock first.

As the boat entered the lock, a crewmember jumped ashore and wrapped a rope around a snubbing post anchored next to the lock. The rope stopped the boat in the lock. Working the snubbing post took a steady hand. If the rope was too tight, the boat would crash into the side of the lock, or the post would snap, sending the boat into the gate at the far end. Too loose and the boat crashed into the gate as well.

Once the boat was snubbed into the lock, the locking process could begin. Generally, the whole process of locking a boat through the gates took about ten minutes.
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Details
HM NumberHMAQ
Series This marker is part of the Susquehanna and Tidewater Canal series
Tags
Historical Period19th Century
Historical PlaceRiver
Marker TypeHistoric Structure
Marker ClassHistorical Marker
Marker StyleFree Standing
Marker ConditionNo reports yet
Date Added Thursday, September 4th, 2014 at 11:38am PDT -07:00
Locationbig map
UTM (WGS84 Datum)18S E 406075 N 4379055
Decimal Degrees39.55605000, -76.09328333
Degrees and Decimal MinutesN 39° 33.363', W 76° 5.597'
Degrees, Minutes and Seconds39° 33' 21.7800" N, 76° 5' 35.8200" W
Driving DirectionsGoogle Maps
Area Code(s)443, 410
Can be seen from road?No
Is marker in the median?No
Closest Postal AddressAt or near Park Dr, Havre de Grace MD 21078, US
Alternative Maps Google Maps, MapQuest, Bing Maps, Yahoo Maps, MSR Maps, OpenCycleMap, MyTopo Maps, OpenStreetMap

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