... be very slightly discolored from 18 or 19 to 21.57 feet below. At 21.57 the corrosion increased for 4 feet, then very rapidly disappeared leaving it bright copper. This agrees with the report of Mr. Baldwin which was at 19.4 below the surface of the pond. By the recent building of the Cradock dam the level of the lower lake has been reduced (and consequently its area, slightly), and as the tides no lon...