The velocities are thus, seriatim: 13 feet, foot, 9 feet, 21 feet, 9 feet, 33 feet, 14 feet, 173 feet. Whoever has driven a horse may know what is the result of giving an impetus and slackening speed at such hap-hazard. As for the earnest suggestion for the adoption of heating by downdrafts, we beg to suggest that Mr. Jencks's committee of 1871 left this an open question. They complain that the champions of this method have not presented any reasonable plans of alterations, and say that the changes made under their direction will make it easy hereafter to adopt a downward ventilation if adequate results are not obtained. They were afraid to shoulder what they call a total revolutionizing of the arrangements of the building, involving an expenditure of $700,000 and over on the House side, as per Engineer Stimer's plan. We herewith present a plan which does not require any revolutionizing of the present arrangements. Indeed, we take advantage of, and fall back upon, many of the ideas originally entertained and incorporated in the building, as per report of General Meigs to the Secretary of War in the year 1853, which was indorsed by Professor Henry, the Secretary of the Smithsonian Institution, and by Professor Bache, the Superintendent of the United States Coast Survey. At that early time, the problem was in its infancy; but it has stood the test, and has been introduced with success since that time in some of the most successful and largest structures in Europe, prominent among which is the Grand Amphitheater of the Conservatory of Arts and Trades in Paris, finished in 1864; the Houses of Parliament; and many of the largest halls in England, and so on. The feasibility of introducing downward heating and ventilation for the hall of the House became clear to us only after a thorough study of all the details of the present apparatus, locating its component parts with mathematical accuracy on plans and sections of the building, as taken from actual measurement, and comparison of same with photographs in circulation among officials and professional men. If the heated air had to pass out from the ceiling of the coil-chamber, the heat would do what it does not do now, it would regulate itself. In cold weather, when the pressure is kept up at a high mark all day, it would pass through hot steam-pipes for the whole height of the coil, while, as the weather moderated, it would pass between a less quantity of hot steam-pipes exclusively, as is now sometimes the case, and explained before; this because the heated air in its upward movement would reach the ceiling of the hall, while now it takes a route worse than that of a camel's back gradually weakened by age, as illustrated by the quaint steam-boxes in the hot-air ducts, and at last broken as by a straw, at, or rather before, the commencement of the present session of Congress. We are not blind partisans of downward ventilation. We are well aware that for a class of huge structures, with enormous chandeliers, like opera-houses, which are exclusively used at night, the heat created by thousands of gas-lights has been most effectually made use of for inducing regular upward currents of the foul air; but it is of record that in no successful modern structure of this class the fresh warm air is allowed to pass through the building right up to the ceiling without doing any good service, as for instance in the case of the large floorregisters in rear of the members' desks in the hall of the House. Invariably, the air is made to escape through registers in rear of pit, boxes, and galleries, to be sucked by "aspiration," as it is called, into the main outlet-ducts, in which a draft is produced by the heat from the gas-lights. A suggestion repeatedly made before this, that a person be stationed in the loft for regulating the louvers under the skylight in the roof, according to the frequent changes of the intensity of light in clear or cloudy weather, is respectfully called attention to. With the adoption of down-draft heating, the space between the skylight in the roof and the light-panels in the ceiling should be encased with galvanized iron, and painted on inner side with a light tint, so as to reflect light, which will be beneficial in cloudy weather, as well as in clear weather, when the louvers have to be partially closed to shut out the direct rays of the sun. Among minor details, we suggest to have thermometers and hygrom eters in various parts of the hall communicate by electrical apparatus with the room of the engineer in the cellar, so as to do away with the old-fashioned chase from the cellar to various parts of the hall, and inverse, which is now necessary to give satisfaction. It is impossible to know the exact state in which the machinery and piping now is, still we can guarantee that all improvements suggested could be carried out within the sum of fifty thousand dollars, and any required guarantee could be easily obtained to insure complete satisfaction. 9.-REPORT OF THE SPECIAL COMMITTEE ON MUDDINESS OF THE POTOMAC WATER. The special committee to whom was referred the resolution of the House of Representatives regarding the muddiness and impurity of the Potomac aqueduct water, have the honor to report: That the matter of the impurities which at times have rendered the Potomac aqueduct wa ter offensive to sight, smell, and taste has frequently commanded the attention of the board of health, and chemical examinations and microscopical inspections of the water have been made to ascertain the causes of such impurities, as will more fully appear by reference to the several annual reports of the board. The muddiness is due to an occasional extraordinary flow of surfacewater, caused by heavy and continuous rains, the melting of ice and snow over an extensive surface of upturned soil along the banks of the river, and the numerous streams flowing therein; that this muddiness occurs particularly during the early spring, when the frost leaves the ground in a spongy and soft condition, easily dissolved or carried away by water flows. At other seasons, the growth of vegetation retards the flow of the surface-water, thus giving it time to soak through the earth. thus causing the water to undergo a process of filtration through the substrata of sand and gravel lying at some distance below the surface. Vegetation is not only a mechanical but a chemical system of purification, for foul water passing through the soil imparts life to the plant through the cellular tissue through which it passes, giving up elements for the nutrition of the plant. It is by this operation, and the natural purification by sand and gravel, that foul water entering a field comes out fresh and pure as spring-water. Another source of the impurity of water at certain seasons, particularly during the summer, when the wa ter is rarely disturbed by storms and rains, is what is common to all stagnant waters, namely, the generation of animal and vegetable life, as confervæ, algæ, and infusoria. The heat of the season also contrib utes to the propagation of said vegetable and animal life. This has occurred in our rivers, streams, and reservoirs several times, when the water became very offensive, at least to the olfactories. These plants and animalcula generate very quickly, and in a very short space of time the surface is covered with them; but their organization is so imperfect that a heavy rain or a strong wind destroys them, and the water then becomes sweet as quickly as it became foul and offensive. After a strong wind, the shores of our reservoirs have been found to be covered with a green vegetation, cast upon them by agitation of the water; the water is then clear. OUR people have often been alarmed at the condition of the water in summer, and have attributed the foulness and bad smell to the presence of fish or spawn; but that is an error, as the reservoirs are protected by screens, through which only the minutest fish can pass, and, moreover, living fish would not impart to the water the offensive smell that characterizes it. An occasional fish may get into the waterpipes, die, and putrify, and when this is found it will suggest that as the cause of the trouble; but in that case the trouble would only be local, not general. The differences in the kind and quality of animalcular life depend not merely upon temporary storage in reservoirs, but also upon the condition of these as to cleanliness. If they contain much mud and sediment and accumulation of organic matter, then we may look for the presence in abundance of minute annelids, or worms. Reservoirs are exposed to light, air, and the sun; the air depositing on their surface many of the animalcules contained therein, and the water finds through light and heat an excellent field for propagation. It is well known that distilled water exposed to air and sun soon becomes alive with animalcules and putrid from their decomposition. So it is with reservoir-water and with sluggish rivers. The surface becomes covered with algæ, a nucleus for the shelter, growth, and development of the infusoria. Instead of being decomposed fish, as was supposed, that occasionally gave bad smell to the water, it is this decomposition of this imperfect vegetation and animal life that gives rise to the formation of sulphureted and phosphorated hydrogen, so offensive to the smell. Filtration will remove the infusoria, as well as the algae, and purify the water, even from mud. In London, the various companies have adopted the system of filter-beds; but the process is very expensive. From Mr. Theodore B. Samo, assistant engineer of the Washington aqueduct, we learn that from the best authorities it is assumed that half a cubic foot of water per hour per square foot of the sand floor is a fair exponent of the best English practice, and is a rate which, with the usual attention, will be certain to insure satisfactory results. on This rate, Mr. Samo calculates, is equivalent to 893 United States gallons per square foot per diem. Assuming the size of a filter-bed for such a city as Washington to be one acre, this area gives a filtration of 3,909,510 gallons in twenty-four hours. To filter 23,000,000 gallons, now used in the city, seven filters of this size would be necessary, the supposition that the flow of water through six of them is continuous through the twenty-four hours. Even these filters, to be successful, would require a subsiding reservoir. This process would entail a very great expense at present, yet the time will come when the popula tion of Washington will be so great as to imperatively demand filterbeds for the purification of the water. The construction of the aqueduct was commenced during the admin istration of President Pierce in 1853, when the population of Wash ington was about fifty thousand inhabitants. It was then considered by Captain Meigs, then chief engineer and architect of this magnifi cent work, to be of ample size for the purpose of that population; but that population has increased threefold since then, and the draft upon the reservoirs is consequently so great now that the water is in constant and rapid motion-not permitted to rest and settle-and must therefore come in the condition as it is issued from the river, muddy or otherwise, to the consumer's spigot. Running water, and particularly the water of our Potomac, that is fed by rivulets and streams that in their turn are often swollen with the muddy drains of a clay soil, requires rest for the deposit of the solids it holds in suspension. The present reservoir is not of sufficient area to afford that rest, and supply the city with water at the same time. In five days, the city of Washington would exhaust every drop of water in the reservoir if the feeding-pipes were locked. Five days of settling would hardly be sufficient to clear the water to satisfaction; but even if it did, the flow from the Potomac could not be interrupted for that length of time, because from the moment that the quantity of water is lessened in the reservoir just in that proportion the pressure is lessened, and before one-half of the water were drawn from it, one-half of the city of Washington would be deprived of water on account of the pressure lost at the reservoir. Hence that rest cannot be secured. In Paris and London, to secure rest to the reservoirs for potable water, there are introduced two systems of water-supply; one to carry the potable water, the other the water for washing, culinary, manufacturing purposes, &c. The quantity of potable water needed by a city is greatly less than water for other purposes; hence two reservoirs of the same size, one containing drinking water and the other water for other purposes, would be subject to a different rapidity of motion. The one from which less water is drawn would have time to settle, and would therefore give water a great deal purer than the other. But even this system is too expensive for our city. The distributing reservoir receives, when the conduit runs full, eighty million of gallons every twenty-four hours. This divided by one hundred and fifty thousand, our present population, would seem to give one hundred and twenty-three gallons per capita. This seems immeuse when it is considered that in England seldom are more than twenty-four gallons allowed. But our public buildings, manufactories, street-washers, fountains, &c., use up a very large proportion of that supply, and, moreover, our American people are fond of water, and we hope never to see the time when they must be stinted in that salutary commodity. Your committee is aware that the waste of water in the public service and by the citizens has been a cause of great complaint; to prevent this waste regulations have been promulgated, meters suggested, &c. But your committee dares assert that not a drop of water is wasted in the city of Washington; for every drop of water that escapes, even through the negligence of our people, is a minute scavenger and a drop of health. Water is not wasted that runs into our sewers and carries miles and miles of filth therein deposited every minute of the day. And your committee dare moreover assert that the health and mortality of a sewered city is just in proportion to the quantity of water that flows through the sewers. Hence, as sanitarians at least, we could not recommend any check upon the use or abuse of water. But we do recommend, inasmuch as an inexhaustible water-power is within our reach, that more water be brought to the city, and that more reservoirs be built to allow the water to settle and come into our houses in a purer condition. Major General Meigs suggests the erection of a reservoir in the northeastern section of the city, to be filled during the night by the present water mains. This plan has at least the recommendation of being an economical one. For seven or eight hours of the night, but little water is drawn from the pipes, and is therefore a loss of seven or eight hours of supply; a night reservoir would collect and distribute it the next day, a clear gain of nearly one-third of the water supply. Major-General Babcock, and his assistant, Mr. Samo, think that the present distributing reservoir might be extended, and thus supply the deficiency. It would be an incalculable good to Washington if both propositions were adopted and carried out. To the question of the committee, inquiring whether, if the Potomac water were uniformly distributed through Washington, it would secure greater pressure, Mr. Samo answers, "Comparatively inferior distribution of water can be insured in any city if it is divided into districts, each district mapped in reference to altitude, and provided with a main proportionate to its area." The quality of the Potomac water is shown by the analysis made last year under the direction of the Surgeon-General of the United States Army. The following table is the result. The quantities are in ten millions, or so many milligrams in ten liters of water, equivalent to so many grains in one hundred and seventy-one gallons. Of course, these are the products of decomposition of animal and vegetable matter. The Potomac water is as regards hardness rather better than the average of river-waters, being 10.4 degrees Clarke's scale. Your committee conclude therefore that one or two more reservoirs and watermains would not only secure to our people a sufficiency of water, but water that would well compare with the purest water supplied to any other city. Respectfully submitted. WASHINGTON, May 2, 1876. 18 B H T. S. VERDI, M. D., Committee. |