APPENDIX D D D.

NORTHERN AND NORTHWESTERN LAKES-SURVEYS-CORRECTING ENGRAVED PLATES-PRINTING AND ISSUING OF CHARTS.

REPORT OF COL. O. M. POE, CORPS OF ENGINEERS, BVT. BRIG, GEN. U. S. A., FOR THE FISCAL YEAR ENDING JUNE 30, 1894.

UNITED STATES ENGINEER OFFICE,

Detroit, Mich., July 10, 1894.

SIR: I have the honor to transmit herewith, in duplicate, my annual report on the "Issue of the published charts of the Northern and Northwestern Lakes and surveys made for the purpose of keeping these charts up to date," for the fiscal year ending June 30, 1894. Very respectfully, your obedient servant,

O. M. POE,

Colonel, Corps of Engineers, Brt. Brig. Gen., U. S. Army.

Brig. Gen. THOMAS L. CASEY,

Chief of Engineers, U. S. A.

DDD I.

NORTHERN AND NORTHWESTERN LAKES-SURVEYS-CORRECTING ENGRAVED PLATES-PRINTING AND ISSUING OF CHARTS.

The sundry civil act of March 3, 1893, appropriated the following amounts for the fiscal year ending June 30, 1894:

Survey of Northern and Northwestern Lakes.-For printing and issuing charts for use of navigators and electrotyping plates for chart printing, two thousand dollars. For surveys, additions to, and correcting engraved plates, twenty-five thousand

dollars.

Under the first item the issuing of charts has been done in Detroit, Mich., from this office, the rest of the work required being attended to by the office of the Chief of Engineers, in Washington. During the fiscal year nearly all charts have been sold at the uniform price of 20 cents each. A few special lithographic charts have been sold for 10 and 5 cents each, and some charts have been issued free of charge for the official use of Government agents applying for them.

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The following table shows the extent of this business:

Issue of the charts of the Northern and Northwestern Lakes during the fiscal year ending

The sum of $911.15 was turned into the Treasury from sale of charts. Total number of charts distributed to July 1, 1893 Distributed, etc., during fiscal year.

194, 399 4,931

Total distributed to July 1, 1894....

199, 330

Under the second item of the above appropriation a number of charts have had corrections and additions made upon them in this office, and have been forwarded to Washington in order that the necessary changes might be made upon the engraved plates.

The following charts have been amended in this office:

The information embodied in the above charts was derived from the best available sources of information. This work has been seriously impeded by lack of sufficient funds. The work is essential, however, if the charts are to be used for navigating the lakes.

The following progress on the combined chart of Lake Superior, scale 1:400,000, has been made: Completed 845 miles of inshore and offshore hydrography and 800 miles of shore line with the adjoining topography 3 to 5 miles back from shore, taking in the latest topographical and geographical information. The hydrography commences at Pigeon River, United States boundary line, and extends around the northwest coast and along the south shore to Pictured Rocks. The topography commences at Carltons Peak, on northwest shore and extends from this point to Pictured Rocks. The topography on the eastern end of Lake Superior and on both sides of St. Marys River, extending from Point Iroquois and Gros Cap to Little Rapids, has been reduced from resurvey, St. Marys River, 1893, and inked in.

Extensive alterations are being made to chart No. 1, St. Marys River, showing section 1 of the 20 and 21 foot Channel and the Hay Lake improvement. For this purpose the chart is being extended so as to take in Middle Neebish. The head of Collingwood Channel is also to be added to this chart. The cities of Sault Ste. Marie, Mich., and Ontario are to be reduced from the field sheets of the resurvey of St. Marys River, 1893. The alterations in this chart are very nearly com pleted.

Mr. Edward Molitor has had charge of this work, and when not engaged on other work has devoted his whole time to it, with his wellknown intelligence and skill.

RESURVEY ST. MARYS RIVER.

The increase in the draft of vessels navigating the Great Lakes and their connecting waters has rendered the resurvey of certain localities necessary. A large number of artificial changes have been made in the channels and harbors, and data obtained fifty years ago in the narrow or rocky parts of the waterway is not sufficiently accurate for a navigation twice the depth of that at the time these surveys were made. In conformity with the general plan of resurveying certain localities, a resurvey of St. Marys River was commenced in May, 1892, at an estimated cost of $64,080. Work was suspended on June 30, 1892, on account of the exhaustion of funds available. Four thousand dollars was allotted for fiscal year ending June 30, 1893, and $20,357.43 for fiscal year ending June 30, 1894. Work was resumed in January, 1893, and has been continued to date.

On June 30, 1893, a field observatory had been constructed at Sault Ste. Marie, Mich., on land belonging to the United States. The astronomical instruments and electrical apparatus necessary for the determination of latitude and longitude had been placed in position.

The observations for a fundamental determination of latitude had been made; eight primary stations definitely and four approximately located; a base line had been measured and the computations made; a line of precise levels had been run from Sault Ste. Marie to Bay Mills, Mich., and the computations nearly completed.

OPERATIONS DURING THE FISCAL YEAR.

Astronomical work. The computations for the latitude of the east pier of the observatory at Sault Ste. Marie were made. Latitude of east pier, 46° 30′ 06.25" north. Reduced to west pier, 46° 30' 06.27" ± 0.08"; the latter latitude was used in the reduction of the triangulation. Observations for the difference in longitude between the west pier, Sault Ste. Marie Observatory, and Ann Arbor (meridian circle) were made and the computations completed. Sault Ste. Marie Observatory (west pier) west of Ann Arbor (meridian circle) 2 minutes 27.995 seconds 0.036 second. Taking the best obtainable data for the longitude of Ann Arbor, 5 hours 34 minutes 55.25 seconds west from Greenwich, we have Sault Ste. Marie Observatory (west pier) west from Greenwich hours 37 minutes 23.25 seconds or 84° 20′ 48.75". This value was used in the reduction of the triangularion. Observations and computations for the azimuth of the line Sault Ste. Marie Observatory to azimuth were made. Azimuth, 178° 06′ 38.87". This value was used in the reduction of the triangulation.

Continuous latitude and azimuth.-For the purpose of obtaining additional data in regard to the recently-discovered movement of the pole,