3. The Low Summer Water

The stage of water called "low summer water," or "ordinary summer level," had been found by Mr. James Stewart to correspond with a bench-mark established by him on Pig Island, Coteau Rapids, when that bench-march was one foot out of water, which result was confirmed by the observations of the undersigned. Before the survey was actually commenced, eight different bench-marks were established in the lower Rapids. They were frequently examined during the summer, and the variations in the stage of the water were always found to be simultaneous and nearly equal throughout the Rapids. Between the 2nd of June and 11th of November, the difference between the greatest rise and the greatest fall which occurred during that period did not exceed one foot three inches. The rise and fall in Lake St. Francis was found to be about the double of the corresponding rise and fall in the Rapids proper. The fluctuations in Lake St. Louis are more considerable than those in Lake St. Francis, and differ from them in their periods and extent, the River Ottawa exercising much influence upon the stage of water in the former Lake. At the lowest stage of water observed, Mr. Stewart's benchmark was found one foot and six inches out of water, and the river having been uncommonly low this fall, it may be surmised that extreme low water is six inches lower than the ordinary summer level, i. e., low summer water. The undersigned have therefore adopted Mr. Stewart's bench for low summer water, and have reduced their soundings to that datum.

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This volume was digitized from the collections of the Marine Museum of the Great Lakes at Kingston