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various plans and reports proposing changes, finally recommended as follows:

WASHINGTON, D. C., February 2, 1877.

The board find that the measures which have been taken to give an increased supply of fresh air to the Hall of the House of Representatlves, in accordance with its recommendation in its previous report, have been followed by good results, and that the test of actual experience, during both cold and warm weather, bas shown that the Hall can be satisfactorily heated and ventilated with the system now employed, namely, that of upward currents, and that this can be done without causing discomfort to the occupants.

The recommendations of the board beretofore presented were intended to meet the great wavt existing, namely, that of an increased supply of air without the production of uni leasant draughts, and also to remove or mitigate certain sources of impurity which were found to exist in the basement of the building.

These recommendations have been only in part carried out, owing to the want of funds, for, although the sum estimated for by the board, namely, $8,000, was duly appropriated from the contingent fund of the House at the close of the last session, yet it appears that this appropriation was only partially available, since the contingent fund was exhausted.

For this reason it bas been found impossible by the architect to provide the means for that increased supply of fresh air to the galleries which the board consider as necessary.

The board bas collected information as to the practical results obtained in large halls of assembly in this country and in Europe by the systems of beating and ventilation adopted, and from these, as well as from the observations and experience of its members, it bas arrived at certain conclusions as to what should be done looking to the permanent arrangement for heating and ventilating the south wing of the Capitol, which may be stated as follows:

1. That it is not desirable to change the present or upward system of ventilation of the Hall of the House of Representatives for any system of so-called downward ventilation, and it is not possible to apply any so-called natural system of ventilation, by means of windows and openings in the ceiling and walls ouly, to a large assembly hall like this.

2. That while the quantity of fresh air which can now be supplied to members on the floor without causing unpleasanr draugut is probably sutficient under ordinary circumstances, it is desirable that there should be means to increase it when needed.

3. That the supply of air to the galleries should be largely increased, and that tbere should be means provided for furnishing cooler air to the galleries than is supplied to the floor of the Hall.

4. That the system of brick flues beneath tito floor of the House should be removed, and galvanized iron flues substituted so far as necessary.

5. That a duct should be constructed to briug the fresh air required for the use of the House to the injecting-fans from a point on the lower terrace and tbrough an ornamental shaft about thirty feet bigb.

6. That an attempt should be made to regulate the amount of moisture in the air supplied, and to cool the air in warm weather.

7. That for this purpose, as well as for other reasons, the course of the present freshair duct should be changed, and the heating coils removed from their inaccessible and inconvenient position, and that the point for admission of fresh air beneath the floor shall be ceptial, instead of in one corner, as at present.

8. That additional means of ventilation shouid be supplied for the npper lobbies.

9. That an attempt should be made to so arrange a system of outlets for foul air in the roof that the wiud can only produce an increased flow of air outwardly.

If tbis can be done snccessfully, the exbaust-fans now in use will become available for ventilation of the basement and lobbies.

10. That means of communication by a system of electric signals be provided between the floor of the House and the engine-room.

11. That the whole matter of heating and ventilation of the south wing of the Capitol should be placed under the control of one person, who is to be held responsible for their proper working. Under the present system, or rather want of system, the board do not believe tbat any apparatus can be made to work satisfactorily.

If it is desired that the board shall continue to interest itself in the heating and ventilating of the House, and in the devising of the best means of carrying out its recommendations, it is extremely desirable that the person who is to have charge of the apparatus when complet-d should be in some way associated with the board, not only to carry ont the experiments and observations which it may deem necessary, but to become familiar with wbat is to be done, and with the apparatus and machinery decided to be best adapted for doing it.

12. Plans have been prepared by the Architect of the Capitol for the alterations

recommended, and these are berewith submitted. The total cost of making these changes, and of putting the heating apparatus in good order, including the purchase of 20,000 feet of new steam-pipes, is estimated at $33,000. All of which is respectfully submitted.

JOSEPH HENRY, Secretary of the Smithsonian Institution, President of the Board.

THOS. L. CASEY, Lieutenant-Colonel Corps of Engineers, Member of the Board.

EDWARD CLARK,
Architect United States Capitol, Member of the Board.

F. SCHUMANN,
Civil Engineer, Member of the Board.

JOHN S. BILLINGS,
Surgeon United States Army, Secretary of the Board."

As provided by law, the changes and improvements recommenıled abore have been madle, which are tbus described by Mr. Robert Briggs, engineer, who bas ably assisted in this work:

During the recess of Congress, the followi cha bave been effected in the arrangements of the apparatus for ventilating and beating the south wing of the United States Capitol.

The necessity of pure and fresh air supply for the purpose of ventilation being fully admitted, there has been a cbange made in the place from which the air was taken previonsly, by the construction of a subterranean duct or passage, leading from a point 200 feet direct from the building, and about the save distance from the streets, below the terrace, west of the Capitol, to the fan, which injects the air for the Hall of Representatives.

It is believed that in tbis location the air will not have been vitiated or impaired in purity in avy degree, either frm the Capitol itself, or from the city beyond the grounds; and when the tower, of 30 feet height, proposed by the commission of ofticers of the United States, to whom this question of ventilation was referred, shall have been finished, it is deemed certain that the purest air attainable in the city Wasbington will bave been used for the ventilation of the Hall.

The immediate and especial advantage of this alteration will be the avoidance of odors from the machinery or boilers, which are located in close proximity to that part of the building wbere the supply-mouth of the fans was in the first instance.

The large fan (16 feet in diameter) and its engine, (of about 60-horse power,) as originally constructed, bave been put in as good condition as when new, twenty years ago, and again possess the capability of supplying 50,000 cnbic feet of air each minute during the cool season, and 100,000 cubic feet in the same length of time in hot weather when tbe necessity for the larger volume exists, to give relative comfort.

An entire change bas been made in the ducts leadivg from this fan. A great deliverymain now passes from it in the cellar, to near the center of the building, whero one of the large central rooms has been taken for a beating-cbamber, and provided with coils of pipes, to be beated by steam ; after passing this chamber, the warmed air enters a second large chamber, where it can be deprived of dust, supplied with desired moisture, and otherwise treated, to render it more pure and healthful.

From this chamber the current of air separates into two ducts, which lead upward through the basement story of the building to the two parts of the Hall situated on either side of the central passage. Each of these ducts terminates, that is, ceases to be a main, in an inclosed chamber or end beneath the floor of the Hall; which chamber has openings in several directions.

These openings are months of branches of distribution, and serve to place under control the supply of air to any part of the Hall.

Some of tbem lead immediately to the space under the circles of the deske, wbich is now entirely open, the brick ducts and passages, wbich bad become disused in the previous changes of desk arrangement, baving been cleared away and removed. Within this circle ihe distribution of air can now be wade general and equal all over the floor. Other openings from the chamber lead to the space without or beyond the circle of desks; wbile yet others lead to the galleries exclusively, by large air-passages passog upward in the walls of the coat-rooms, so tbat a great independent supply of air is provided for the galleries.

This gallery supply is in addition to former provisions, and will unquestionably relieve the ventilation of the hall, by substitution of fresh for vitiated air in the galleries themselves, by preventing a diffusion of vitiated air into the body of the ball, and especially in tending to preclude currents of air by making the supply general throughout the room.

To give some idea of the magnitude of the provision for supply of air to the Hall, in

the way of air ducts of passages, it will be stated here that the main air-supply duct, leading to the fan, has a cross section of area of 120 square feet.

The main delivery-duct, from the fan to the heating chamber, has 80 square feet of area. The two mains to the fi vor of the Hall have each 40 square feet of area. Of the distributing branches under the floor of the Hall, those which lead to the south gallery (two in number) will bave each 14 sqnare feet; those leading to the north gallery (also two in number) each 7 square feet. The sizes of these distributions will be such as to require the full supply from the delivery-branches. These distributing-branches under the floor of the circle of desks, and under that of the galleries, bave been made of sheet iron, and so arranged that distributions from all branches are controlled by regulators to insure proper local action.

For the escape of foul air from the Hall the former provision of distributed openings in the ceiling bas been thought ample and well arranged to remove the current uniformly over the whole surface. But the inadequate dimensions of the outlet for discbarge above the roof has been corrected by the construction of a louvered ventilator, arranged to be closed at either side, in opposition to the winds. This ven,ilator has more than 140 square feet of unobstructed area on either side for the efflux of air.

With these provisions for supplying and getting rid of large volumes of air, the means of controlling its temperature, at all times and at any moment, has been materially amended, especially when the condition of the great coil and its chamber, as they formerly were arranged, is considered.

In the new arrangement of coil-cbamber the materials of the old coil, most of which were unimpaired by time or service, were reconstructed to form four sections or masses of pipes, containing in all 45,000 feet, or nearly nine miles of pipes of one inch diameter, (pomival.) There sections occupy the lower part of the chamber, and are inclosed by a sbeet-irou covering separating them froin the upper part. In front of these sections (in the direction in which the air enters) and of the space above them is placed a partition of iron louver blinds, so that by opening the lower blinds the cold air comes upon and presses among the pipes, and is warmed, or by opening the upper blinds the air enters above, and passes over the coil. These contrivances enable the air to be tempered to any degree of warmth at any moment.

Wben properly manipulated in cool weather, warmer or cooler air is at the command of the operator, as occasion may require, without waiting for heat to be imparted to or removed from the heating coil; while the pipes are not open to the difficulty usually attending steam-heating, of the likelihood to freeze the lower tubes in the attempt to regolate the heat of the air-supply.

After the hot and cold currents in proper proportion will have passed throngh or above the coil, they are commingled in the cbamber bebind the coil in part, and in the preparatory cban ber afterward, until one current of uniform temperature is provided for supply to the distributing ducts and branches.

The appliances for treatment of air, regulating its moisture, and for cooling it in summer, have been essayed, but with the kpowledge of repeated effort in these directious, accompanied with repeated failure of any essential or important result, it can only be claimed that the success of these appliances is problematical. The room, however, bas been provided for prosecuting the trials without interfering with the working of the apparatus at any time. Both steam-jets and water-jets bave been furnished to supply any amount of moisture desired.

There being no loss of heat by the walls or floor of the Hall of Representatives at any time or in any season, and the loss of heat at the ceiling being overcome by the great and constantly ascending current of vitiated air from the Hall. (supposing the adequate ventilation, equal to 50,000 feet per minute, which empties the Hall each 10 aninutes, were provided,) it follows that no bot air is ever needed for its ventilation.

That is, that 70° temperature of air is too warm to introduce when the Hall is crowded, in the cold weather, and 650 to 68° are needed to keep the room down to 700, if tbis be tbe accepted temperature of comfort.

Consequently, the difficolty to be encountered is, how to introduce the large volume of comparatively cool air, needed to procure freshness to the senses, without having currents blowing upon the persons occupying the desks or benches.

To solve this difficult problem every advantage has been taken in the changes made this year to make available any portion of the room not occupied by sittings.

Within the circle of the desks the risers of the platform have been left perforated as before, but means have been taken to control the amount of air entering at them, so that no defined currents along the floor shall be propagated. Tbe sides or risers of the aisle-steps have also been provided with numerous perforations, so disposed that currents from them shall meet and be diffused by opposite corrents.

About the Speaker's desk numerous openings have beeu made, with every precantion for diffusing the emerging currents: and it is in contemplation to put registers or small platforms near many of the desks, which shall be perforated, to allow escape of air.

Beyond the circle of desks the large registers are retained in the corners as the best

way of preserving eqnality of distribution in these localities, but the great reliance is on the numerous small registers in the walls, which will now be adequately supplied with air.

In the coat-rooms the small registers also will now suffice in amount, while in the galleries the air-supply is now provided to be equal, if necessary, to that elsewhere in tbe hall.

It may not be tbat a perfect success in ventilation will be attained at the first trial of the new arrangements, but it is certain that the control of the means is now so completely in the hands of those who direct the system that any change can readily be effected at will.

As the heating and ventilating apparatus is now arranged, it is capa ble of supplying all the fresh air that inay be required, and is so ad. justed as to furuish warmer or cooler air, as causes for such changes in the temperature in the chamber may occur.

With attentive and intelligent management, I feel confident that this new arrangement can be made to give all the satisfaction the nature of the case will admit; that is, the air will be furnished in adequate quantities; will be chemically the same as that of the external atmosphere, and will be delivered at any fixed temperature that may be required.

It is proper to state bere that I feel indebted to Mr. Lanuan, engineer of the heating department of the House, for his cordial and intelligent co operatiou in the changes.

CAPITOL GROUNDS. For full information relating to the work done on these grounds, and showing their present condition, I insert a portion of the report made to me by Mr. Cobb, engineer:

In making the third annual roport of the improvement of the Capitol grounds, ac. cording to the plans of Mr. Fred. Law Olnisted, landscape architect, and carried on uoder your direction, I have the honor to stare that the work has proceeded satisfactorily, and as rapidly as the amount appropriated would allow.

In consequence of the appropriation being small, ($125,000,) the men have been kept on half time during eight months of the year.

The number of names on the pay-roll is 126. From June 30, 1876, to June 30, 1877, there were 23,3287 days' labor performed by the inen, aud 2,7714 days' work of horses, at a cost of $54,064.85.

This includes, however, $7,473.04 expended on the rolls for ventilation of the House of Representatives, and $1,585.45 paid by vouchers for special work.

All material bas been purcbased at the lowest narket-price, and fully up to the standard called for in the various contracts and specifications.

The intense heat duriog the summer of 1876, parcbød part of the grass sown during the spring, and some of the plantings were res-oder in the fall. Most of the trees and shrubs survived, the total loss being two large and twenty-two small trees. Tbe lawns are kept closely cropped, and the sod is exceptionally firm and compact.

On account of the total lack of police, the deprelations among the small shrubbery have been numerous-one hundred and fifty shrubs being taken from various parts of the grounds, and one hundred plants removed from the fountains in the east park alone. Five of the trees mentioned above as dying were destroyed by boys. A large number of cattle have been caught trespassing, bat, as most of the depredations were committed after working-hours, the greater part could not be prevented.

During the year thirty-three large and fifty small trees have been moved by the trucks.

One hundred oriental plane trees and one hundred and eighty-six choice plants were inported. Altogether 7,837 plants and trees have been set out.

Since the last report, the drives, then under contract, leading from First street west to the top of the hill, both north and south, and the approaches from Delaware avenue portb, and New Jersey avenue south, have been laid with bituminous concrete pavements.

This work, as a whole, is satisfactory, but in parts exhibits a tendency to soften under the heat of the sun, and in some instances has required extensive repairs, which the contractors have promptly made, th- terms of their contract requiring them to keep the pavement in good order for three years.

That laid on the west end of the north drive is especially faulty in this respect, but the rapid evaporation of its volatile oils may bring it to the right consistency in apother year.

The pavement laid at the Delaware avenue entrance is of little value, except its base

of hydranlic concrete. This is excellent, but the top being unequally mised, gives both good and bad results.

Bids were open.d June 19 for laying asphalt pavements on the drives of the East park. After a thorongh examination of the different proposals, the award was tipally inade to Crawford & Hoffman, for about 6,431 square yards vulcanized asphalt; to W. R. Davis & Co., for about 12,783 square yards Grahamite and Trinidad asphalt; and to W. H. Groat, for 750 yards of Van Camp's patent pavement. This work is now in progress.

I would respectfully call your attention to the fact that heavily-loaded wagons are continually being driven over the roadways, injuring them for pl-asure-driving, as well as destroying the privacy of the park, by converting it into a thoroughfare.

There have been 68,700 square feet of artificial stone foot-walks laid. This has proved a valuable substitute for stone, at a cost of less than one-third. Some defects bave appeared, due principally to the expansion of the material, but these are easily remedied at a slight cost.

It appears to wear no more rapidly than sandstone, and is much more easily adjusted to the winding walks and constantly-changing grades.

A three-foot brick sewer has been partially constructed in the West park, to extend from the center of the grounds to Souh B street, there connecting with the large Government sewer, which, when completed, will substantially complete the sewer system of the park.

The fountains in the East park have not yet been completed. Seven hundred and thirty-tive feet of 12-inch water-pipe and 300 feet of sewer-pipe, besides a double-acting steam-pump, and the necessary jets and fixtures inside the vases, are noeded, to put them into working order.

One ornamental iron trellis has been placed on the north walk of the East park, and a similar one is now being erected on the corresponding walk on the south side.

A low granite coping and wall, to inclose the northern half of the East park, bas been contracted for, and is now being put in position.

A screen-wall, with ornamental ramps and piers, is under contract for the circle at the head of Pennsylvania avenue west and along First street.

This will be completed during the fall and winter.

AIR-DUCT.

The air duct for ventilating the Hall of the House of Representatives is located on an extension of the north building-line of the House, and extends from the northwest corner of the bnilding, under both terraces, a distance of 164 feet, to a temporary opening. It has been constructed in tbe most substantial manner with stone side walls and a brick arch. The walls vary in thickness at the bottom from 3 to 41 feet, according to the nature of the foundation and the depth below the surface. The width of walls at the spring of the arch is 24 feet, being carried up ver. tically to a level with the top of the archi, affording a secure backing for the brick-work. The width between walls is 7 feet on bottom and 8 feet ou top, with a beight of 10 feet.

It was commenced April 1 and finished June 15, at a cost of $3,264.85, or $19.90 per livear foot.

'EXPENDITURES FOR THE YEAR 1876.

Amount paid for grading
Amount paid for soil
Amount paid for sodding
Amount paid for manure and other fertilizers.
Amount paid for sand
Amount paid for gravel...
Amount paid for trees and plants
Amount paid for grass-seed
Amount paid for sewer-drainage
Amount paid for water-service...
Amount paid for gas-service ...
Amount paid for lamp-piers on East Capitol grounds.
Amount paid for curbing and edging
Amount paid for iron-work, (ornamental trellis)
Amount paid for cement..

$1,935 69 2, 315 50

144 91 878 00 363 96

863 72 1,932 63

223 00 2, 292 72 2,072 93

457 60 1, 316 17 2,534 95 1, 285 00 1, 254 40

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