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- Description:
- One blueprint drawing entitled "U. S. Lake Survey, Detail of Intermediate Sweep Float." The drawing shows the design of a float (buoy) that was used as part of a sweep for obtaining water depth information. The sweep consisted of a line of 15 floats with flags, spaced at 100-foot intervals, that supported an underwater wire at a set depth. The line of buoys would then be dragged across an area of water by launches at each end of the buoy line. If the wire encountered any submerged obstructions, it would cause one or more float (buoy) flags to tip and thereby give an approximate location of an obstruction that could be investigated further. Such obstructions could then be plotted on the navigational charts that were produced by the Lake Survey Office. The plan is dated January, 1915.
- Date Issued:
- 1915-01-01T00:00:00Z
- Data Provider:
- Detroit Historical Society
- Collection:
- Maritime
- Description:
- One navigational chart entitled, "Manitou Passage, Lake Michigan." The chart was "Prepared from U. S. Surveys and first issued under the direction of Major W. L. Fisk, Corps of Engineers, U. S. Army, in 1902." It was later revised and "published under the direction of Lieut. Colonel Mason M. Patrick, Corps of Engineers, U. S. Army, in 1915." The chart was drawn at a scale of 1:30,000 and covers about 20 miles of the Manitou Passage just north of Glen Arbor, Michigan. The chart includes information such as soundings in feet, lake bottom characteristics, shoreline details, lighthouses, lines of latitude and longitude, and sailing directions. The chart was printed in black ink on white paper and was published by the U. S. Lake Survey Office. Land areas are colored pale yellow and shallow areas of the lake are colored light blue. The chart was "Issued January 12, 1916" with "Aids to navigation corrected from information received to April 16, 1920."
- Date Issued:
- 1920-01-01T00:00:00Z
- Data Provider:
- Detroit Historical Society
- Collection:
- Maritime
