1. Surveying Operations.
The examination of the Channel was made in parallel lines, soundings being taken in the usual manner; the surveying barge used on the occasion was provided with tubes through which measured poles could be passed to any depth and easily moved up and down, a mode of operation which was also made use of for the purpose of ascertaining whether or not the Channel was obstructed; whenever a doubtful spot was found, a more close examination was at once resorted to, and when it was ascertained to be necessary, a thorough survey of the locality was made.
It is hardly necessary to remark that to make a Marine Survey it is required that a triangulation of the adjacent shore lines shall be made, and proper stations established, from whence sights can be taken to the surveying vessel; at the Galoppe Rapids and the North Channel of the Long Sault, the obstructions being concentrated in one spot, the necessary stations could easily be established on a measured base line on shore, and no triangulation was required. But between Lakes St. Francis and St. Louis the obstructions were found to be so numerous and extensive that it became necessary to survey that whole portion of the river, and consequently to complete the triangulation made in 1852 by Mr. James Stewart, C. E., which embraced the Coteau and Cascades Rapids ; their labors in this particular are apparent on the Maps accompanying this Report.
Having accomplished these preparatory operations, which, from the great number of islands, the width of the river, and the difficulties of communication, required considerable time and labor, they proceeded to the examination of the different Channels in the following manner.
The mode of surveying by sounding on lines between stations on shore, or to and from buoys, could only be made use of where the current was not strong, and had to be abandoned in the Rapids proper. Here the swell below the Chutes, and the current above, make it impossible to move a vessel with any degree of accuracy, and even the mere crossing in a boat is generally impracticable. The only available mode of operation, and therefore the one adopted, consisted in anchoring scows at convenient distances one from another across the current, determining the position of these from the station ashore, and then in dropping down life-boats on measured cables. Each life-boat was manned properly with a Captain at the helm, an experienced man to take the soundings with a measured iron or wooden pole, and an assistant to book them. For every one or two hundred feet, which the boat descended, a flag was raised, and the position of the boat determined instrumentally, from at least two stations on shore, by assistant engineers. It can easily be conceived that labor of this character occupies much time, because only one line of soundings can be taken from each anchorage, and because the moving of scows across the current, with a view of placing them in position, is attended with great difficulty, and sometimes with danger. It was frequently impossible by one day's hard work to obtain more than one single line of soundings, and more than one day was entirely lost when a scow dragged her anchor in consequence of the extraordinary swiftness of the current, for in such instances no other alternative was left but to give up the anchorage, and to run down through the Rapids; and to return to the original position, it was necessary to pass up the Canal. Another great delay was found in hauling up the life-boat to the scow from whence it had started, a slow operation, which required the utmost exertion of the men. In certain places the water was so turbulent, and the current so swift, that it was not only difficult and dangerous to anchor the scows, but even to board them with the boats when at anchor was attended with danger. The difficulties became in certain localities insuperable, and recurrence had to be had to so-called running lines, an operation which consisted in letting boats run in different directions through the Rapids, taking soundings from them, and at proper intervals showing a flag to which sight could be taken simultaneously, and with at least two good instruments on shore. These lines of soundings were protracted in the usual way. With a good boat well steered and manned, this last named mode of operation was found to be practicable in even the worst places, and where the open boats could not live, the iron barge built for the purpose was used.
It was by employing alternately, and as circumstances would dictate, the different modes of operation above described, that the soundings were obtained, a portion of which only could be marked upon the Maps which accompany this Report. The aggregate number of soundings taken and recorded in the field books amount to over 28,000.
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