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“Bite-Size Bits of Local, National, and Global History”
Havre de Grace in Harford County, Maryland — The American Northeast (Mid-Atlantic)
 

How a Lock Works

 
 
How a Lock Works Marker image. Click for full size.
By Beverly Pfingsten, July 1, 2007
1. How a Lock Works Marker
Inscription. 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.
How a Lock Works Marker image. Click for full size.
By Allen C. Browne, October 4, 2013
2. How a Lock Works Marker
The Thomas J. Hatem Memorial Bridge (US 40) crosses the Susquehanna in the background.
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.
 
Marker series. This marker is included in the Susquehanna and Tidewater Canal marker series.
 
Location. 39° 33.363′ N, 76° 5.597′ W. Marker is in Havre de Grace, Maryland, in Harford County. Marker can be reached from Conesto Street 0.2 miles from Erie Street. Touch for map. Marker is in this post office area: Havre de Grace MD 21078, United States of America.
 
Other nearby markers. At least 8 other markers are within walking distance of this marker. The Susquehanna and Tidewater Canal (here, next to this marker); Nineteenth Century Travel (within shouting distance of this marker); The Lock House (approx. ¼ mile away); Susquehanna River Crossing (approx. ¼ mile away); Under Attack (approx. ¼ mile away); Susquehanna Lower Ferry (approx. 0.3 miles away);
Restored lock of Susquehanna and Tidewater Canal at Havre de Grace image. Click for full size.
By Beverly Pfingsten, July 1, 2007
3. Restored lock of Susquehanna and Tidewater Canal at Havre de Grace
See "The Lock House" marker for photos of the toll colector's office and home.
Old Post Road: Susquehanna Lower Ferry (approx. 0.3 miles away); Matilda O'Neill Home (approx. 0.3 miles away). Touch for a list and map of all markers in Havre de Grace.
 
Categories. Industry & CommerceWaterways & Vessels
 
Operating the Lock image. Click for full size.
By Allen C. Browne, October 4, 2013
4. Operating the Lock
Close-up of image on marker
Locking Through image. Click for full size.
By Allen C. Browne, October 4, 2013
5. Locking Through
Upper Sluice valves are opened and water in lock is raised to level of upstream canal. Upper gates are opened and boat enters lock ❶. Upper gates and their sluice valves are closed. Sluice valves in lower gates are opened, allowing water to empty from lock ❷. The boat is lowered slowly as the water in the lock drops to level of downstream canal. Lower gate is opened and boat proceeds on lower level of canal ❸.
Close-up of image on marker
 
 
Credits. This page was last revised on June 16, 2016. This page originally submitted on July 1, 2007, by Bill Pfingsten of Bel Air, Maryland. This page has been viewed 1,572 times since then and 25 times this year. Photos:   1. submitted on July 1, 2007, by Bill Pfingsten of Bel Air, Maryland.   2. submitted on October 10, 2013, by Allen C. Browne of Silver Spring, Maryland.   3. submitted on July 1, 2007, by Bill Pfingsten of Bel Air, Maryland.   4, 5. submitted on October 10, 2013, by Allen C. Browne of Silver Spring, Maryland. • J. J. Prats was the editor who published this page.
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