In the north abutment a waste culvert has been constructed, with suitable gates of cast iron, to draw the water down in the reservoir at such times as it may be necessary, to facilitate the making of any repairs that may be required, and to discharge the river at ordinary times during the construction of the work. From this abutment the old channel of the river was filled by an embankment, with a heavy protection wall on the lower side, which was raised 15 feet above the waste weir of the dam, and designed to be 50 feet wide on the top, but was not completed the full width, when the unprecedented flood of January, 1841, carried it away. The embankment stood well, and gave no indications of failure, until the water rose to near the surface, and passed through between the frozen and unfrozen earth about 20 inches below the top. After the breach was made in the embankment, large masses of heavy ice came down from the reservoir, which soon broke down the unfinished protection wall, and carried off nearly the whole embankment. The masonry of the dam and abutment sustained but little injury. Such a flood had not been anticipated, and the water way proved insufficient to pass it off. Had the embankment been completed the full width, and the protection wall carried up to the full height it was intended to carry it, the work might have proved adequate to the emergency. It was determined to fill the gap made by this breach, (about 200 feet long,) by a structure of hydraulic stone masonry, adapting 180 feet as waste weir. This work presented all the difficulties it was originally intended to avoid, by carrying the work partially into the hill. It was necessary to form an artificial foundation, and carry up a heavy body of masonry, in the channel of the river, which in some parts had 15 feet in depth below its ordinary level; subject in ordinary seasons to frequent and sudden floods, and affording no means to form another channel for it to pass, until the work could be accomplished.