observed at Milwaukee, Wis. It is a horizontal plane 8.33 feet below the bench-mark on Dr. I. A. Lapham's house, Poplar street, Milwaukee.

Mean level. The mean level of Lake Michigan, as observed at Milwaukee from January 1, 1860, to December 31, 1875, inclusive, is 11.39 feet below bench-mark on Dr. Lapham's house.

Milwaukee, Wis.

Bench-marks. (1.) The bench-mark on Dr. Lapham's house is the top of the brick water-table east side of main door. The part exposed is 4 inches by 1 inch.

(2.) Stone monument in court-house square, near the southeast corner thereof, in the seventh ward. It is 51.36 feet above the plane of reference.

(3.) Stone monument on sidewalk at southeast corner of Eighth and Chestnut streets, second ward. It is 49.27 feet above the plane of reference.

(4.) The highest point of the stone water-table at the corner of the building, Ludington's block, northwest corner of East Water and Wisconsin streets. It is 9.61 above

the plane of reference.

Zero of gauge.-The zero of gauge is the highest point of a nail-head driven into a large pile supporting platform at the corner of the railroad warehouse, foot of Poplar street, south side of street. It is 1 foot above the plane of reference.

Check-point. The check-point is on the north side of the center pier of the swingbridge over the river, between Chestnut and Division streets. It is the top of a copper bolt 1 inch in diameter, leaded into the stone. This point is 1.86 feet above the plane of reference.

Escanaba, Mich.

Assuming that the surface of the lake was level during the months of June, July, and August, 1874, by comparing the observations at Milwaukee and Escanaba for these months it is found that the zero (May, 1874-July, 1875) at Escanaba was 3.39 feet above the zero at Milwaukee. Hence the Escanaba zero was 4.39 feet above the plane of reference.

Bench-marks.-The bench-marks at Escanaba are:

(1.) The top of the water-table of the large brick building of S. Adler, on the northwest corner of Ludington street and Douseman avenue, on the southeast corner of the building. It is 8.64 feet above the plane of reference.

(2.) The top of the water-sill of the Escanaba light-house, at the north side of the front door, against the brick wall. It is 3.16 feet above the plane of reference.

Zero of gauge.-The zero of gauge is the highest point of the head of an 8-inch spike driven into a beam of the main dock of the Goodrich Transportation Company, west side, and at junction of bridge with main dock. It is 0.78 feet above the plane of reference.

Check-point. The check-point is the highest point of the square head of an 8-inch spike driven into a timber of Oliver's dock, foot of Smith street, on west side of dock, near junction of main dock and bridge. It is 1.12 feet above the plane of reference.

Port Austin, Mich.

Assuming that the surfaces of Lakes Huron and Michigan were each level, and of the same level during the months of June, July, and August, 1874, by comparing the observations at Milwaukee and Port Austin for these months it is found that the zero at Port Austin is 6.19 feet above the plane of reference for Lake Michigan.

Bench-mark.-The head of a 6-inch bolt leaded into the rock, 13 feet southwest of the gauge. It is 6.19 feet above the plane of reference.

Zero of gauge.-The reading point is the upper edge of a board nailed to one of the studs of the gauge-house. The zero is an imaginary point, 4 feet below this, and on the same level as the bench-mark mentioned above.

Check-point.—The check-point is the top of the head of a bolt leaded into the rock, (0 feet northwest of gauge-house. It is 1.23 feet below the plane of reference.

Lakeport, Mich.

Assuming that the surfaces of Lakes Huron and Michigan were each level, and of the same level during the months of June, July, and August, 1875, by comparing the observations at Milwaukee and Lakeport for these months it is found that the Lakeport zero is 3.38 feet above the plane of reference for Lake Michigan.

Bench-marks.-(1.) A spike driven into a cedar post supporting the steam grist-mill of John Cole, post being on north side of mill, and 12 feet from northwest corner. It is 9.78 feet above the plane of reference.

(2.) A cross (X) cut in the stone on the east side of the engine-house of the gristmill, and at the southeast corner. It is 6.52 feet above the plane of reference.

(3.) The highest point of the top stone of the foundation of the milk-house of Mr.