actually comes from the bottom of the hall, though a large proportion may enter from the hall-corridors in rear of the galleries, by means of the doors, which are so frequently open.

A number of conditions contribute largely to the vitiation of the House atmosphere, prominent among which is the promiscuous crowd which frequent the galleries and lobbies, not a few of whom are desirable candidates for the bath-tub and crash towel. These beings find in the seats convenient lounging and sleeping corners, their bodies giving out the greatest impurities, and their places supplied not unfrequently, when they retire for the night, with regiments of diminutive cavalry in light marching order. Under the most favorable conditions, the air becomes more or less charged with effete organic matter exhaled from human bodies. This not only combines with carbonic acid when the air is heated, but, when chilled, descending, becomes absorbed and retained by all porous material, especially upholstery. Hence, if pos sible, all such substances should be excluded. On the floor of the House, the seats should be covered with the least absorbable material, as polished leather. Frequent washing of floors, walls, &c., and periodical attention to the cleansing of carpets, constitute important sanitary measures, not to be neglected. Everything which by possibility affects the purity of the air enters into a proper system of ventilation.

Another subject inviting attention in this connection is the sewerage, which has not hitherto received the attention its importance demands. Until the fall of 1875, the sewer draining the United States Capitol discharged its contents into the open Washington Canal. This canal has been converted into a main sewer for a length of 3,000 feet beyond the mouth of the Capitol sewer. (See map No. 3.) This main sewer drains 3,000 acres, or one-half of the whole area of the city level for this entire distance south of the Capitol sewer, and for the space of 1,500 feet higher up to Pennsylvania avenue; and, since sewer gases seek the highest point, the Capitol sewer, which now enters it freely, forms a sort of ventilating shaft to this new sewer, on account of its ascent up the line of Capitol Hill. The mouth therefore of the Capitol sewer ought to be effectively trapped, and a shaft built over the trapped part for easy access and control in case any sediment should be deposited therein. A sketch (No. 4) is herewith presented showing that to clean this trap will require no more labor than is needed for traps at the corner of two intersecting streets. It is not believed, as has been recently asserted, that the mouth of this sewer is now under water, since the level of the (tide) water is no higher in the present sewer than it was in the old canal, when the mouth of the Capitol sewer was always exposed in ordinary tides, although submerged during spring tides and freshets.

If a radical change in the heating and ventilating be entertained, as we hope it will be, we shall recommend that the fresh air (warm or cold, as the case may be) be forced in from the ceilings, where the warm air, in consequence of its smaller density, will be rapidly diffused over the whole surface of the ceilings, cool off in contact with ceiling and side walls, and be slowly pressed downward, followed by succeeding layers of hot air until it comes in the region of the ventilating or foulair registers, through which it will be removed from the hall by the action of the exhaust-fans with a low velocity; thus the movement will uninterruptedly proceed as long as the proper balance between the action of the supply and the exhaust machinery is maintained by intelligent and faithful engineers.

We do not see any practical difficulty to this arrangement. The air from the present coil-chamber, instead of being forced down into the

present main hot-air duct, would rise to, and above, the high ceiling of the coil-chamber, to the level of the ceiling of the hall. Thence it would be forced over the ceiling of the hall with no more difficulty than is now met underneath its floor. The outer tier of the glazed panels of the ceiling, 32 in number, is hardly of any use for light. Ducts constructed of two thicknesses of sheet-metal, with an interstice filled with non-conducting material, such as ground pumice stone, ashes, &c., should be tightly fitted to a properly-shaped outlet, from the highest point at or above the old coil-chamber. The ducts should be extended all around the ceiling over the above-named tier of panels, and openings on the lower face of the ducts should be tightly fitted to those panels. These panels have not at present perpendicular open spaces of about 1 inches in width. for the escape of foul air. The height of this space would hereafter be so regulated as in the aggregate to present the most favorable sectional area for the ingress of the fresh air, which will be forced in with a low velocity.

The present doorway from the coil-chamber to the main hot-air duct would be walled up, when the net-work of the present hot-air ducts would, with the slightest modifications and alterations, be made available for use as foul-air ducts by simply constructing connecting ducts with the down-draft stacks, which are in convenient proximity. The efflux of the foul air should be provided for through the boxes at the side-walls of the hall near its floor, through a few floor registers, and through openings in the risers of the passages between the amphitheatrically-arranged seats, but the open risers under the feet of the members should be closed, as objectionable to comfort and health of the members. The proposed compound system of impulsion and exhaust hinges upon the preponderance of the force by which the fresh air is driven in through the ceilings and upon a moderate action of the suction by the exhaust-fans, so as to avoid a suction of air and consequent drafts through the 39 double doors leading to the House hall from corridors. By following this principle, the open fire-places in the retiring rooms around the hall will be more important auxiliaries of the new system, which would not be the case in any plan similar to the one we propose, but in which the exhaust process of the foul air would preponderate, since in the latter case the smoke from the fire-places would be drawn back into the hall and thus be in conflict with the system much more than at present.

it is believed that when the ducts admitting the fresh air, as well as those discharging the foul air, are brought under perfect control by confining the current of air within the required sectional area, there will be a vast gain in the useful effect of the present machinery. The sectional areas of the supply-ducts at present increase and diminish, branch off, diverge, wind in all possible directions, and at times open altogether in the dead spaces below the risers of the House floor, which want of system must result in a most serious waste, and must impair its efficiency. In recapitulating, we beg to state that, besides the thorough remodeling of the system of heating and ventilating the House hall, we propose, by way of modification of the present system:

1. The raising and perfecting of upper end of upcast shaft for discharging foul air.

2. The ventilation of the cellar by constructing a duct from kitchen to the upcast shaft.

3. Attention to the ventilation of the ranges of water-closets on the ground-floor of the building.

4. The careful trapping of the Capitol sewer at its junction with the Tiber main sewer.

5. Re-instatement of the hydration of the hot air.

6. A lining of the hot-air ducts near their junction with the coil-chambers with tin. This will be only necessary for a limited distance and need not be extended into the smaller ducts.

7. Proper guards should be put in by which the fresh air in its rapid course is arrested at the numerous narrow slots through which warm air is expected to reach the warm-air register at the side-walls of the hall. To come up to the standard of the present time, some steps should be taken during the next recess of Congress to increase the power for the supply of fresh air, and this is a feature of our proposition looking to mere changes of detail, as well as of those advising a thorough revisal of the whole system with its shiftless labyrinth of air-ducts under the floor of the ball.

In conclusion, it may not be out of place to outline the exact calculations by which the scientists of our day have proved the utter insuffici ency of the arbitrary assumptions so recently in vogue. Man exhales daily 173 cubic feet of carbonic acid at 32°, which at 65° expands to 18 cubic feet. Exhaled air contains four per centum of carbonic acid, and consequently these 18 cubic feet of that gas are distributed through 472 cubic feet of air, which each individual absolutely needs for respiration. If the air does not return to the lungs charged with four per centum of carbonic acid, then for each quantity of exhaled air an equal amount of fresh air must be introduced into the room. This minimum, however, is by no means the correct expression of the smallest want, since it can not be assumed that such an intense mixing and motion of the air result from it, that, on the one hand, the carbonic acid would be equally dis tributed, and, on the other, the exhaled air would be removed so fast that no part would be returned to the lungs. To obtain success, the above 472 cubic feet must be multiplied with at least eighty, in order, proba bly, to obtain air charged with no more carbonic acid than 5, which is the normal ingredient of outside air. But since the diffusibility of the gases is never so uniform that this condition is reached, there are still found, with such a ventilation of 1,575 cubic feet per hour and head, from eight to ten parts of carbonic acid in ten thousand parts of air. These figures appear to be high; still the experiments of Morin, Pettenkoffer, and many others of world-wide reputation, agree in this respect.

Carbonic acid serves as an indicator of miasmatic contents and other deteriorations in the air, and, as such, is used in argument to simplify the problem.

The maximum contents of water in healthy air is one-tenth pound in 2,100 cubic feet, the quantity required per head and per hour in conditions similar to those existing in the hall of the House of Representatives. The actual contents of the air should neither exceed the maximum not be much below it; for dry air, resulting from the abstraction of moisture from the human body, produces a peculiar sensation of headache and dizziness. If the aqueous contents, on the contrary, are in excess, the lungs cannot expel as much water as the organism requires, and thus transpiration, or perspiration, is rendered impossible. The products of transpiration, or perspiration, i. e., sweat and evaporation, will, with the, exception of aqueous vapors, be likely to escape chemical analysis, but are perceptible to the olfactory nerves.

We have now disposed of the subject presented for our consideration as we have been able in the limited time allowed and consistently with other pressing duties. If not presuming, the board would respectfully

suggest that they be authorized to prepare for the consideration of the next session of the present Congress an elaborate and full report, suggesting such methods as will secure the best possible sanitary conditions both in the Capitol proper and the various other public buildings in which Government work is conducted, in which heating, lighting, sewerage, and ventilation are defects of the most serious character and extent, calling loudly for correction. A reference to the Third Annual Report of the Board of Health (pages 43-44) will fully illustrate the disgraceful insanitary conditions of the Government buildings. A very moderate appropriation, to be strictly and economically applied, would enable the board to institute suitable experiments, and avail themselves of the experience and co-operation of distinguished scientists, in maturing a report covering the entire field of sanitary reform, and embracing suggestions and propositions of practical value and importance. We have the honor to be, very respectfully, your obedient servants, CHRIS. C. COX, M. D., D. W. BLISS, M. D.,

T. S. VERDI, M. D.,

Committee.

SUPPLEMENT.

Mechanical detail.

Five boilers of nearly 5 feet diameter and 15 feet in length are at present at disposal for generating steam for heating the coils, for forcing the air in, for the exhaust fans, for the bath-rooms, wash-basins, and so on. The generating power thus seems not very contracted, but after eighteen years' use some of the flues have most likely become defective. These boilers should be throughly overhauled after the recess. A fan-wheel of increased power for the supply of fresh air, and an engine of enlarged power to drive it, will be indispensable for reaching a higher standard of ventilation, while the present exhaust-fans are deemed ample.

There were formerly four large coils of steam-pipes in the heating-apparatus for the hall, but of these one was taken out last summer, so that this winter there were only three coils in the old chamber, leaving a large unoccupied space, which is unfavorable for the regular working of the apparatus; the fourth coil has evidently been taken out because after eighteen years' use it had become leaky and inefficient. An examination shows that whole sections of the coils still in use are in the same condition; that the heat is shut off from those sections, and that the concerned piping is just so much dead material in the coil, obstructing the passage of air without doing any service whatever. As at present arranged, the whole coils are filled with steam, when the hall is being heated up in the morning, with about 12 pounds pressure on the coils, but, except in extreme cold weather, a pressure of but about 24 pounds is used for the rest of the day, when only about 4 feet in height of the coils, measured from the upper face down, are filled with steam, and consequently hot. At such time, the air blows irregularly into the main air-duct; a hot puff from the upper part of the coil is often followed by a cool puff through the lower cold part of the coil.

If the present system of heating by impulsion of warm air from the lower part of the hall is maintained, measures should be taken to make better use of the energy exerted by the engine, since at present there is

no due proportion between useful and wasteful work done. The coils should be lowered, the tongue between the lower part of the coils and the hot-air chamber to be lowered also; the three large-sized windows in the outer wall of the coil-chamber should be walled up or made double for economy for heat, and but small openings, filled with thick, hammered glass, for admission of a moderate amount of light, left; the ceil ing of the coil-chamber should then be lowered, so as to be little above the top of the inlet door to the hot-air chamber, to which it should be drawn down with a slow curve, so that the velocity of the currents of air is not abruptly change 1, or that obstacles to their regular movements are found. If, as per some of the reports of the architect, which, it ap pears, are only partially followed, the dead space below the raised floor of the hall is to be used as a resorvoir for the hot air, ordinary caution advises the plastering of the wood-work on the under side. Since the coils are out of repair, and need, at all events, a thorough overhauling, we should recommend, for economy of heat and facilities of repair, that these coils be separated into compartments about 5 feet high each. These coils, instead of having vertical side-interstices all the way up, would thus be set zigzag fashion.

It is remarkable that, on the one hand, one of the four heavy coils has been taken out, and heat has been shut off from many sections of the remaining three coils, and that, on the other hand, this deficiency so created has been compensated by obstructing the inner hot-air duct with patent steam-boxes, or radiators, against all rules derived from the observations of the easy circulation of currents of air or similar gases. If these coils, as at present, were deemed sufficient, why not cut off one-third of the height of the remaining three coils, put that amount of steam-pipe in the now empty space of the fourth coil, decrease the present disproportionate height of the coil-chamber, and let the warm. air pass straight in the warm-air ducts, instead of allowing it to rise high up, and forcing it down again to the level of the warm-air ducts. This would not be mentioned if it were a mere waste; but since there is reasonable complaint about the want of efficiency of the means now at disposal, it is necessary to call attention to anything tending to increase useful effect.

The imperfect use of power generated is still arrangement of the exhaust than in the supply. ent discharge of 470 cubic feet per second; these atmosphere as follows:

more apparent in the Let us assume a preswill reach the external

1st. Through an aggregate area of 350 square feet in openings of ceilings, giving a velocity per second of 14 feet.

2d. They spread in the open loft over an area of 12,900 square feet, giving an average of of a foot.

3d. They pass in the chamber in front of the down-shafts, through an opening having 52 square feet, and resulting in a velocity of 9 feet. 4th. They move into the down-shafts through two openings, aggre gating an area of 22 feet, and resulting in a velocity of 21 feet.

5th. They are drawn through the two down-shafts, which aggregate an area of 50 square feet, and give a velocity of 94 feet.

6th. They issue from the exhaust-fans by two circular pipes of 3 feet diameter, having an area of 14 square feet, and giving a velocity of 33 feet.

7th. They pass up through the upcast-shaft, having a sectional area of 33 square feet, giving a velocity of 14 feet.

8th. They discharge through the mouth of the upcast-shaft, having a sectional area of 27 square feet, resulting in a velocity of 174 feet.