The incandescent oil-vapor system, which produces a light much superior in intensity to the ordinary oil light, and is a strong rival of electricity and acetylene gas, was installed at 45 stations during the fiscal year. Experiments were made toward adding to the reliability of this light, and diminishing the expense of oil consumption, while retaining the efficiency of the lamp within satisfactory limits. Further installation of this system will be made as rapidly as practicable at stations where it is considered practical and desirable. Experimental tests are now in progress for the purpose of improving the fog-signal apparatus now in service, which it is believed will develop valuable results in the near future.

The progress and improvements made in buoyage during the past year were in the further extension of the use of gas buoys of both the Pintsch and acetylene systems, and equipping such buoys with either whistles or bells (aerial or submarine) for particular stations where such combinations are required. Further improvements in the buoys will be in the increased intensity of lighted buoys and their combinations with sound signals, aerial or submarine.

Investigation of acetylene gas as an illuminant in connection with the special apparatus designed and used in connection therewith justifies the statement that it is especially well adapted for light-house purposes.

Experiments have been in progress during the year with a view to improving the incandescent mantle now in use on Pintsch gas buoys, and it is hoped that further valuable results may be obtained in the near future.

A system of buoyage for Ambrose Channel, New York Harbor, which is approaching completion, has been adopted which will, it is believed, meet the requirements of this important deep-water approach to New York. It consists of the establishment of 24 buoys, 4 of which are combination gas and whistling buoys, 4 combination gas and bell buoys, and 16 gas-lighted buoys. This ample provision for the safety of navigation through the channel is made complete by the establishment of what is probably the best light-ship in the world, the Ambrose Channel Light-Vessel No. 87, off the entrance to New York Lower Bay, about 27 miles from the gas and whistling buoy which marks the intersection of the axes of Ambrose Channel and Gedney Channel. The present illuminant of this vessel is an electric arc light, which was substituted for the incandescent light in previous use; her fog-signals are a 12-inch steam whistle and a submarine bell. By the act approved June 25, 1910, Congress authorized the employment of not to exceed 1,750 light-house and fog-signal keepers and laborers attending other lights for the fiscal year 1911, an increase of 50 over the preceding year. It is considered that the number thus authorized will be sufficient to meet existing demands.

Subsequent to the close of the fiscal year covered by this report, the following action has been taken in carrying out the intent of the act approved June 17, 1910:

The light-house districts have been rearranged and their number increased from 16 to 19, and an inspector assigned to the charge of each district. One of these new districts comprises Alaska. The growing importance of this territory warrants an increase in the aids to navigation, and a number are now being installed. The other two new districts are Porto Rico and Hawaii. Officers of the Engineer Corps of the Army have been assigned as inspectors in the districts which embrace the Mississippi River and its tributaries; officers of the Navy have been continued as inspectors and have been given general charge in the other districts.

Officers of the Engineer Corps of the Army have been continued on duty with the Bureau of Light-Houses in these districts also, as provided in the act, but have been relieved of the charge of routine repair and construction work. In each district the office forces and lighthouse tenders have been combined under a single head.

The reorganization under the act of June 17, 1910, promises to result in a considerable economy, and to this end plans have been made for a consolidation under one officer in each district of the office forces, light-house tenders, and the entire routine management of the affairs of the district.

The estimates will be submitted in a form which will permit of the purchase of all supplies for the Light-House Service under a single item of the appropriation, which should result in economy in office work and in the use of the appropriations.

COAST AND GEODETIC SURVEY.

FIELD WORK.

Good progress has been made in the collection and preparation for publication, in the form of Charts, Coast Pilots, Tide Tables, and Notices to Mariners, of all obtainable information useful to navigators and relating to the coast of the United States and to the coasts under the jurisdiction of the United States.

The demand for surveys in Alaska continues, and all of the vessels and men available for the purpose have been employed in charting unsurveyed waters in that Territory. Surveys were made in Portland Canal, Tongass Narrows, Cordova Bay, Controller Bay, Prince William Sound, Cook Inlet, Nushagak Bay (in Bristol Bay), and in the vicinity of Kodiak.

In the Philippine Islands the charting of the unsurveyed portions of the coast is making rapid progress and 10 per cent of the entire general coast line was covered during the year. The work is being done in cooperation with the insular government, as in the past. Surveys were made on the west coast of Samar, north and south coasts of Leyte, north and south coasts of Mindanao, south coast of Masbate, west and east coasts of Mindoro, in Surigao and Tanon straits, and around the Tablas Islands.

Several detached surveys were connected by covering the intervening spaces, and the survey of nearly one-half of the general coast line of the archipelago was completed before the close of the fiscal

year.

The improvement of the long wire drag was continued and a drag more than 8,000 feet long was used in open water. This greatly increased the area possible to be examined in any given time and consequently decreases the cost of the work without any loss of accuracy in making the examination of channels and harbors.

Details in regard to the work assigned to the Bureau and to the Superintendent of the Coast and Geodetic Survey as Commissioner representing the United States in recovering and marking the international boundary between the United States and Canada and in the demarcation of the Alaska boundary are given below.

Reference monuments were established along the United States and Canada water boundary west of Point Roberts to the Pacific Ocean. These monuments were placed in the United States and were connected by triangulation with each other and with the triangulation of the Coast and Geodetic Survey. The survey and re-marking of

this boundary was also extended eastward from the summit of the Rocky Mountains, westward from the west end of Lake Superior along Pigeon River, and along the St. Croix and St. John rivers, on the borders of the State of Maine.

In the survey and demarcation of the Alaska boundary in southeast Alaska progress was made at the head of Portland Canal and at the crossing of the Unuk and Salmon rivers. The survey and demarcation of this boundary along the one hundred and forty-first meridian was completed south of the Yukon River to the Natazhat Mountains, a distance of 200 miles, and considerable progress was made in extending the work north of the river.

In 1908 and 1909 the Superintendent called attention to the importance of extending a triangulation from the initial point of this boundary on the Yukon River down the great valley to its mouth, but no appropriation has been made for this purpose. I approve this recommendation and have made provision for the work in the estimates which have been submitted to Congress.

Work at the latitude observatories at Gaithersburg, Md., and at Ukiah, Cal., maintained by the International Geodetic Association under the direction of the Superintendent, was continued during the year.

An officer continued on duty as a member of the Mississippi River Commission and another was continuously employed in cooperating with the Maryland State Board of Shell-Fish Commissioners as authorized by law.

The water boundary between the States of Louisiana and Mississippi in Lake Borgne and Mississippi Sound as established by a decree of the United States Supreme Court was indicated by placing buoys in position and referring them to the marks previously established on shore.

Observations to determine the relative force of gravity were made in 14 States and Territories and in the District of Columbia.

The standard levels were extended in 4 States and Territories and topographic surveys were made in 7.

Triangulation was done in 13 States and Territories and supplementary triangulation, including the determination of the geographic positions of aids to navigation, was continued along the coasts of Massachusetts, Connecticut, Maryland, Virginia, North Carolina, and the west coast of Florida. This work was completed on the west coast of Florida.

An examination of navigable waters on the coasts of Maine and New York and of Mayaguez Harbor, in Porto Rico, was made with a long wire drag, and other hydrographic work was done in the waters of 11 States.

The magnetic survey of the country was continued by making observations at 238 stations distributed over 39 States and Territories and numerous observations were made at sea on board the surveying vessels on their cruises to and from their fields of work in various portions of the country. These observations were made in the Atlantic and Pacific oceans and in the waters of the Philippine Archipelago. A continuous record was also obtained of the variations in the force of terrestrial magnetism at five observatories equipped with self-registering instruments.

A continuous record of the tidal changes was obtained at 8 stations on the Atlantic coast and at 4 stations on the Pacific coast, including 1 station in Alaska. Self-registering gauges were also maintained at 2 stations in the Philippine Islands. The record of some tide observations of more than ordinary interest were received during the year. These observations were made in the Arctic Ocean by Civil Engineer R. E. Peary, U. S. Navy, and a discussion of them in connection with all the other available data in that region has been made and is ready for publication.

Special surveys were made of the Delaware Breakwater Speed Trial Course and of selected localities in the Hawaiian Islands at the request of the Navy Department, and work was done at the request of the governor of North Carolina to aid in enforcing the fishery laws of that State.

The attendance of two officers of the Survey at the Sixteenth General Conference of the International Geodetic Association, held at London and Cambridge, England, September 21 to 30, as the delegates of the United States, was noticed in my last annual report.

OFFICE WORK.

Progress was made in the various branches of the office work, including computation, plotting, and discussion of the results of the work in the field and the preparation of data for publication by chart or otherwise.

A discussion of the Figure of the Earth and Isostasy from Measurements made in the United States prior to 1906 was published and was received with favorable comments by the foreign geodesists assembled at the Sixteenth General Conference of the International Geodetic Association in September, 1909. A supplementary discussion of this same subject, utilizing additional data to 1909, was also published.

Tables of predicted tides for numerous ports on the coasts of the United States and in foreign countries for the year 1911 were prepared and published.