WHM- The Blackstone Canal - How the Canal Worked

Highway of Commerce: The Blackstone Canal
Industrial Worcester

How the Canal Worked

The Blackstone Canal was built using "slack-water" engineering. Instead of digging a trench for the entire route, engineers made use of the Blackstone River. The canal passed in and out of the river 16 times and ran in the river for 10% of its 45-mile course. This design led to disagreements between the Blackstone Canal Company and mill owners along the river over water rights, and to seasonal operational problems. Construction features fell into three major parts.

Trench and Towpath
The canal trench was generally 34 feet wide at the top and 18 feet wide at the bottom, with a water depth of 4-to-6 feet. The banks cleared at least 3 feet above the water line. Basins and "lay-bys" at landings near the locks allowed for loading and unloading cargoes and for two-way traffic.

The towpath - along which men led horses to pull the boats -was at least ten feet wide. Along trenched sections it ran between the canal and the river, serving as buffer during freshet season. Wooden bridges carried the towpath over streams along the route and across the river in Blackstone and Millbury.

Locks
Locks are the "chambers," 70 x 10 feet and with gates at each end, in which the boats ascended and descended. Most were made of locally quarried granite. To "lock up," water from the higher level was admitted to the lock through small doors near the bottom of the gates. To "lock down," water was drained out of the lock until it reached the desired height. It took about 4 minutes to lift a boat 8 or 10 feet to the next level, and about 3 to lower it. In all, 49 locks (32 in Massachusetts, 7 in Worcester) accommodated the change from sea level at Providence to 168 feet at Woonsocket, to 451 ½ feet at Worcester.

Dams and Reservoirs
Dams and reservoirs held water until it was needed and regulated overall water levels. Reservoirs were natural ponds enlarged by damming. The principal ones were Dorothy (Dority) Pond in Millbury and Long Pond (Lake Quinsigamond) and North Pond (Indian Lake) in Worcester.