PREFACE. This, the first edition of the rearranged H. O. Publication No. 108 B, contains the descriptions of and sailing directions for the St. Lawrence River above Montreal, Lake Ontario, and Lake Erie, including the Detroit River to Detroit. The information embodied in this publication is mainly from the Canadian Sailing Directions for the St. Lawrence River, H. O. Publications No. 108 C and No. 108 D, Bulletin No. 29 by United States Lake Survey Office, H. O. Charts, Lake Survey Charts, and Canadian Charts. It is corrected to Notices to Mariners No. 8, 1921. The bearings and courses are given in degrees true to the nearest degree, followed by the equivalent magnetic bearing expressed in points to the nearest point in parenthesis, thus, with a variation of 5° west, course north true would read 0° (N. § E.). Bearings limiting the sectors of lights are toward the light. The directions of winds refer to the points from which they blow; of currents toward which they set. These directions are true. Variations for the year, with the annual rate of change, may be obtained from Lake Survey Chart No. 0. Distances are expressed in statute miles, the mile being approximately 1,760 yards. Heights are referred to mean lake level. For all details of lights and fog signals, the mariner should consult Light List, Great Lakes, United States and Canada, issued by the Lighthouse Service of the Department of Commerce. Depths.--The datum for the soundings mentioned herein are as follows: The datum for Lake St. Louis corresponds to a depth of 14 feet on the upper sill of the upper lock of the Lachine Canal; to 9 feet on the lower sill of Ste. Anne Lock, and to 15 feet on the lower sill of the lower entrance lock of Soulanges Canal. The datum for Lake St. Francis is the extreme low water of 1895, or 143 feet on the upper sill of the upper entrance lock of Soulanges Canal and 13 feet on the lower sill of the lower entrance lock of Cornwall Canal. The datum between Cornwall and Lake Ontario is that of the sloping surface of the river when Lake Ontario is at level of 243 feet above mean tide at New York. The depths for Lake Ontario herein given are referred to lowwater datum, the reference plane for United States river and harbor improvements, which for Lake Ontario is an elevation of 244.5 feet above mean sea level. Depths on the Lake Survey Charts, referred to standard low water, are generally 13 feet less than those herein published. The depths for Lake Erie herein given are referred to low-water datum, the reference plane for United States river and harbor improvements, which for Lake Erie is an elevation 570.8 feet above mean sea level. Depths on the Lake Survey Charts, referred to standard low water, are generally 1 foot less than those herein. published. (For fuller particulars, see "Notes" on the several charts of the river and lakes.) Caution. The mariner proceeding from Montreal to any port on the Great Lakes will use Canadian Charts, Hydrographic Office Charts, and Lake Survey Charts. The distances, bearings, and the compass roses on these charts differ, so the mariner is cautioned to consult the notes on the chart in use to ascertain the scale and bearing. Summary of Notices to Mariners. While it is the intention of the Hydrographic Office to publish about the first of each year a Summary of Notices to Mariners of the preceding year affecting the volume, it must be understood that these summaries are intended to include only important changes and corrections and that their publication may be discontinued at any time, especially when a new edition of the book is issued. Masters of vessels should keep complete files of weekly Notices to Mariners and supply themselves with the latest List of Lights, and seek from local authorities, pilots, and harbor masters the latest information relative to any special regulations in force in the particular locality visited. Mariners are requested to notify the United States Hydrographic Office, Washington, D. C., or one of its branch offices of errors they may discover in this publication or of additional matter which they think should be inserted. CONTENTS. Page. INFORMATION RELATING TO NAVIGATION ON THE ST. LAWRENCE RIVER AND THE GREAT LAKES. Publications. The principal publications of the United States Hydrographic Office for the use of navigators are: Charts, Sailing Directions, American Practical Navigator, Altitude and Azimuth Tables, International Code of Signals, Light List, Notices to Mariners, Pilot Charts, and Hydrographic Bulletins. Of these the Notices to Mariners and the Hydrographic Bulletins are free to mariners and others interested in shipping. The Pilot Charts are free to contributors of professional information, but are sold to the general public at 10 cents a copy; other publications of the office are sold under the law at cost price, and can be purchased directly from the office or through its sales agencies, but are not sold by Branch Hydrographic Offices. Charts when issued are corrected to date. The dates on which extensive corrections are made are noted on the chart on the right of the middle of the lower edge, those of the smaller corrections at the left lower corner. The edition and corresponding date of the chart will be found in the right lower corner outside the outer neat line. Planes of reference.—The planes of reference for the St. Lawrence River, Lake Ontario, and Lake Erie are given in the preface. Accuracy of chart. The character and accuracy of the survey on which any chart is based determine the value of the chart, and the larger the scale used the more important is exactness necessary. The source and date, which are generally given in the title, are good guides in judging a survey. Besides the changes that may have taken place since the date of the survey in waters, especially where there is sand or mud, the earlier surveys were incomplete and inaccurate as to needed detail; therefore a chart founded on such a survey should be used with caution until thoroughly tested. Except in wellfrequented harbors and their approaches, most surveys made have not been so complete and thorough as to insure that all dangers have been found. The number of the soundings on a chart also helps to estimate the completeness of the survey, but for the sake of clearness the chart is not expected to show all the soundings that were obtained. Sparse or unevenly distributed soundings usually show that the surIvey was not made in much detail. |