This illustration appeared in Harper’s Weekly in 1873, in an issue depicting life among the anthracite coal mines of Pennsylvania.

This sketch shows a weigh-lock on the Lehigh Canal in operation near mining operations in Carbon County. The author provided this helpful description of the operation of a weigh-lock on the Canal:

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The sketch… illustrates the method of weighing the cargoes in the boats.

This is done by running each vessel into the ‘weigh-lock’ of the canal, where the gross weight is ascertained, and by deducting from this the burden of the empty boat (which is made up and registered each spring on the same scale), the net figures are easily found.

This ‘weigh-lock’ is constructed with a movable bottom. While it is full the boat enters it, after which the doors are shut and the water is let out at one of the ends.

The boat thus gradually sinks to the bottom, which is the platform of a scale, registering within the building above.

The weight having been ascertained, the water is again let in, and the boat floated off into the stream.”

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