Two thousand eight hundred and twenty sheets of the maps of the lake surveys have been issued for commercial, harbor improvement, and military purposes during the year, making the whole number of maps called for and issued since these surveys were commenced 27,411 sheets.
Special surveys have also been made during the year, maps issued and forwarded for the use of the department, of Niagara River, Erie, Conneaut, Ashtabula, Grand River, Cleveland, Black River, Sandusky, Saint Joseph's, Grand Haven, Chicago, Racine, and Sheboygan.
The principal labors of the parties engaged in these surveys during the year are comprised in the measurement of 269 1\2 miles of shoreline, 164 1\2 square miles of topography, 187 miles of sounding, and 1,200 square miles of offshore hydrography on 1,586 miles of lines of sounding; the measurement of a base line of 4,173 feet in length; difference of longitude between several distant points by electric observations, and observations by flashing lights; also astronomical observations for the latitude of eight points.
Recommendation.-These surveys are called for by numerous parties and individuals, as well as by commercial men, for private as well as for public use. It is indispensable that some rules and system be established to keep to issue of these valuable maps within such limits as will insure the great objects of the survey, the diffusion of this information to promote national industry, at the same time to prevent them falling into the hands of persons collecting for other purposes than the public good. I recommend that the department be therefore authorized to issue these maps, after supplying the wants for years past has been authorized for distributing the Coast Survey maps. This will prevent an improper use, and enable all persons capable of using them to obtain copies.
The estimate for carrying on the work for the next year is $184,604.42, which exceeds the amount appropriated for last year's operations about $60,000. It is proper to say that this increase of estimate does not contemplate any advance in the wages of assistants, but is simply due to the increased cost of materials and supplies.
On our Pacific Coast Major Williamson, of the Corps of Engineers, has explored and reconnoitered parts of Northern California and Southern Oregon, giving the topography of its roads, and continues observations for barometric correction of altitudes, having also in view an investigation of the formula for determining heights by this instrument. He has traversed and explored the heights of the Nevada Range in Northern California, said to be 10,000 to 11,000 feet above the level of the sea, and the military roads between the coast and this range of mountains to facilitate the military operations of the commanding general. During the year he also examined the various sites on Admiralty Inlet and Puget Sound, that might hereafter become useful for military purposes, and selected such as should be reserved from sale by the Land Office.
PRESERVATION AND REPAIR OF ATLANTIC HARBORS AND SEA-WALLS.
An appropriation was made in 1864 for renewing the construction of the sea-walls in Boston harbor to preserve the headlands from further destruction by the ocean waves, and, as a consequence, injury