The following is a table of the electric lamps now required for public needs:

To determine the horse power required for the above service, which includes all of the public buildings, grounds, and streets of Washington, it is assumed that each 16-candle power incandescent lamp will require 64 watts and each arc lamp 450 watts; that 83 per cent of power at the turbine shafts is effective for incandescent lights and 68 per cent for arc lights, and that four-tenths of the maximum incandescent load may be required at the same time as the full arc load. Under these assumptions 4,458 horse power should be available at the turbine shafts for generating the electricity required for the lights above tabulated, which is 0.70 of the horse power which may be made available without storage at the lowest river stage. The remaining 30 per cent, or 1,937 horse power, can for the present be used for pumping from the United States mains to the high-service area of the city and for other public purposes. We find, then, that electrical power can readily be transmitted from Great Falls to Washington; that there can be constructed, at reasonable cost, a power canal around the falls and a power plant below them; that there are available at the lowest stages of the river 6,395 horse power, without storage of water above the falls in the Seneca reach of the river, and 8,648 horse power with such storage, while 4,458 horse power only are required for the present lighting purposes; and we therefore come to the conclusion that it is entirely feasible to use the water power of the Potomac at Great Falls for the purpose of lighting the public buildings, grounds, and streets of the District of Columbia.

It may be remarked in this connection, that eventually 3,216 additional arc lights will be required for lighting public grounds and streets, calling for 2,853 horse power, and that the lighting of public grounds and streets alone will then require practically all the power available without storage.

Groups (a) and (b) of the table above consist of buildings whose partial or entire lighting is provided for by electric plants operated by individual steam plants already provided. Should none of the water power be applied to their lighting, 2,920 horse power will, for the immediate present, be available for other purposes mentioned above.

But during the past fourteen years the number of street lights in use in the District has doubled. As the increase continues, a time will arrive when the available water power will not suffice for the lighting of all the streets and the public buildings and grounds. Auxiliary steam power will then be necessary. The most economical application of this power will be, not to the lighting of streets, involving the expense of conduits and mains, but to the lighting of buildings, for in these buildings the steam plants may be located and utilized at the same time for motive power or heating, while the losses of transmission and the cost of conductors will be minimized. In the end but one-tenth of the water power will be in excess of the needs for street lighting alone, and this would not be an unreasonable reserve.

ADVISABILITY.

The question of the advisability of using the power of the Potomac at Great Falls for the public purposes mentioned in Senator Manderson's resolution depends on the present cost of lighting the public buildings and grounds, and the streets of Washington as compared with the probable cost of lighting under the proposed system,

and also on the probable cost of the works required for the latter system and the probable cost of operation.

The cost of lighting under the present system and the probable cost under the proposed system. During the year ending December 31, 1893, the city of Chicago operated 1,110 arc lamps from 4 power stations at an average cost of $96.64 per lamp per year, using steam power and underground circuits. This cost does not include interest, depreciation, or taxes. The entire cost of land, buildings, plant, dynamos, lamps, posts, conduits, circuits, and all the other items charged to construction December 31, 1893, was $688,312.80.

The mayor and board of public works of Evansville, Ind., reported February 28, 1894, to the common council of that city upon the feasibility of the city owning its own electric plant. This report contains a list in which are to be found 16 cities, besides Washington, using 300 or more arc lamps. Thirteen are lighted by private contract at an average yearly cost per lamp of $111.12, St. Louis being furnished 2,000 arc lamps at a charge of $75 per lamp. Three cities own and operate their own plant at an average cost per lamp of $85.62, the cost in the case of Wheeling, one of the three, being $62 per lamp for 400 lamps.

June 20, 1894, contracts for lighting some of the streets of the city of Baltimore with electricity were awarded at $127.75 per arc lamp per year. But two bids were received, one for the eastern district, the other for the western district. The partition of the city was made by the companies bidding, which thus avoided the risk of one underbidding the other and enabled both to secure the maximum price for lighting service fixed by ordinance. One company furnishes 635 lamps, the other 404. At present the yearly charge to the District for each arc lamp is $182.50. From these figures it is apparent that this city is paying far above the average charge for are lights, and about double the cost of such lighting to cities owning and operating their own plant. The figures given are based upon the use of steam plant with its expensive coal consumption.

Estimates which are given herewith have been made of the cost of operating a system actuated by the water power of the falls, and they give $52.33 for the cost per arc light per annum.

It has been assumed that each arc light would replace 2.5 gas burners. The present contract price for each gas lamp per year is $21.50; and at this rate the annual cost for two and a half lamps would be $53.75. The estimated annual cost of an arc light is therefore about the same as the annual cost of the gas burners it would replace. The advantage in using the water power of the Great Falls for lighting the streets and grounds of the District will be the increased amount of light afforded for the same annual expenditure.

From the foregoing the board concludes that it is advisable to use the water power at Great Falls for the public purposes indicated in the resolution.

GENERAL PLAN OF PLANT.

The general plan of the plant needed may be outlined as follows: Vertical turbines directly coupled to comparatively low-tension alternating-current generators. The potential of the current to be raised by transformers to 10,000 volts and transmitted by an aerial line to the city limits and thence to a convenient distributing station in Washington, by underground cables, and there utilized to actuate polyphase motors. These motors to be mounted on shafts, to which shall be coupled armatures of directcurrent dynamos, each generating unit to be for 100 or 125 lights.

Without surveys it is not practicable to furnish an estimate of the cost of constructing the canal, but an approximate estimate of the cost of all hydraulic and electric plants, buildings, aerial line, conduits, and lamps is $3,764,930. This is for the utilization of that part of the water power of the falls which is deemed available without resort to storage, i. e., 7,524 gross horse power, or 6,395 at the turbine shafts. This power, even if increased by resort to storage, will not be sufficient to furnish light to private consumers.

Hydraulic plant of 12,800 H. P.*

Building for same..

Estimate of cost.

$64,000

51, 200

109, 710

102, 150

Electric plant

250,000 20,000 492, 600 2,250,000 424, 970

3, 764, 930

*For the reason that the available hydraulic head is liable to be reduced about one-half in times of freshets the plant estimated for is correspondingly increased.

It should be remembered that the above estimates are for a plant capable of utilizing the entire power of the falls without resort to storage, and sufficient for lighting all of the probable future area of the city.

To these estimates should be added the cost of lands, of canal construction, and of annual repairs of canal.

If the plant be limited to the present needs of the city, including the public buildings and grounds and streets, the estimated cost of plant so limited, and not including the cost of wiring buildings, is $2,441,030, and the estimated annual cost of operating the same is $201,790. As far as can be ascertained from the data furnished the board, the expenditure for the year ending June 30, 1893, for the above lighting was: For gas and oil

For electricity from plant not owned by the United States.
For electricity from United States plant..

$187, 991.31

77, 198. 24

29, 968. 25

295, 157.80

METHOD BY WHICH THE RIGHT TO USE THE WATER POWER AT GREAT FALLS CAN BE ACQUIRED, AND WHAT STEPS SHOULD BE TAKEN BY LEGISLATION OR OTHERWISE TO ACQUIRE SAID POWER AND THE LAND NEEDED ADJACENT THERETO. The three riparian owners at Great Falls are the Chesapeake and Ohio Canal Company, the Great Falls Manufacturing Company, and the United States. The lands of the Chesapeake and Ohio Canal Company are mainly cut off from the channel of the river by the interposing lands of the United States, and the proportion of its ownership in the power of the falls must be very limited. The Great Falls Manufacturing Company claims the Toulson tract," on the Virginia side of the river, through which a power canal around the falls would have to pass and on which, below the falls, buildings containing hydraulic machinery would have to be constructed. It is also owner of Conns Island, above the falls, which island is the basis of claims still pending against the United States for damages to the water rights of the company. The United States is the owner of several pieces of riparian property at the falls, and although the proportions of the water rights at the falls belonging to the respective riparian owners have never been determined, judicially or otherwise, it appears to be certain that the United States is by far the largest of these owners.

There is now pending in Congress a bill (S. 1359 and H. R. 7280), of which a copy is transmitted herewith, entitled "A bill to amend an act approved July 15, 1882, enti

tled 'An act to increase the water supply of the city of Washington, and for other purposes."" The bill provides for the acquisition by the United States, by the right of eminent domain or otherwise, of all the lands and water rights at Great Falls not now owned by the United States. It has been favorably reported by the Senate Committee on the District of Columbia (copy of report also herewith), and it appears to provide a fair and equitable method by which the water rights referred to can be acquired.

RECOMMENDATION.

For the reason that there were no funds provided for the use of the board, none of the surveys required for determining the location of the power canal and power plant at Great Falls that would be required for utilizing for electrical purposes the power of the falls now wasted and the cost of these works could be made.

This cost, the cost of the necessary works in this city and of the line connecting the two systems, will be so considerable that they should not be undertaken before plans have been very carefully and elaborately worked out, and the board therefore begs to suggest that to this end there be enacted a provision of law similar to the one contained in the District appropriation act of August 6, 1890, which authorized the appointment by the President of a board of electrical, etc., experts, to consider the location, arrangement, and operation of electric wires in the District of Columbia; and the board also suggests that there be immediately appropriated the sum of $10,000 to meet the expenses of the said board.

GEORGE H. ELLIOT,

Colonel, Corps of Engineers. JOHN G. D. KNIGHT,

Captain, Corps of Engineers.