shape of an inverted siphon. The immense and expensive structure which has been described, was deemed necessary, by the legislature, to prevent obstruction of navigation of the Harlem river.

The greatest depression of the Clendinning valley is 50 feet below the top of the aqueduct, and the valley is 1,900 feet across. Streets cross the line of the aqueduct in this valley at right angles. The aqueduct passes the valley on a bridge, and archways are constructed over three of the streets. The archways for each street are one for carriage-way of thirty feet span, and an arch on each side for side walks of ten and a half feet span. The style of masonry is the same as that of the Sing-Sing bridge. That part of the bridge which has no provision for street arches is composed of a continuous wall of masonry, carried up on a bevel of one twelfth its rise to the grade line of the aqueduct, where it is thirty feet wide. The outside or face of this wall, for one foot in breadth, is laid in hydraulic mortar, and the remainder is dry masonry, consisting of courses of large stone, with the insterstices thoroughly filled with small broken stones.

The receiving reservoir is formed with earth banks, the interior having regular rubble walls, and the outside is protected by a stone wall laid up on a slope of one horizontal to three vertical; the face laid in cement mortar, and the inside dry. The inside is protected by a dry slope wall laid on the face of the embankment, which slopes one and a half horizontal to one vertical. The embankments are raised four feet above the top water-line and vary in width from eighteen to twenty-one feet. Vaults or brick archways are constructed, in which iron pipes are laid, so arranged that the pipes from the northern division of the reservoir connect with those of the southern division, and thence pass off to the distributing reservoir, and to supply the adjacent districts. The vault on the eastern side is 540 feet long and is 16 feet span; that on the western side is 400 feet long and 8 feet span. The pipes are all provided with stop-cocks, and so arranged that they can receive water from either division, except one pipe from each division leading to the distributing reservoir. A pipe is put through the division bank with a stop-cock, to allow the water, or not, to pass from one division into the other. The aqueduct intersects the reservoir at right angles with its westerly line, and 252 feet south of the northwesterly corner. At this

point a gate-chamber is constructed, with one set of gates to pass the water into the northern division, and another set to pass it into a continued conduit of masonry constructed within the embankment of the reservoir, to the angle of the southern division, which the water there enters by a brick sluice. This arrangement gives the power of directing the water into either division, or both, at the same time. A waste-weir is constructed in the division bank. It has not been deemed necessary to complete the excavation of this reservoir. It has at present a capacity for 150,000,000 imperial gallons.

The distributing reservoir is built upon ground higher than any part of the city south of it. The walls are built upon a foundation sunk five feet below the grade of the streets, and are of hydraulic stone-masonry, constructed with openings, to reduce the quantity of masonry and give a more enlarged base. The openings are made by an exterior and interior wall, connected at every ten feet by cross-walls, which are carried up to within seventeen feet of the top, and then connected by a brick arch thrown from one to the other, and the spandrels between them levelled up solid, and a course of concrete put on the whole six inches thick, which reaches a level ten feet below the top on which the exterior wall is carried up single to the top. The exterior wall has a bevel of one to six, and is uniformly four feet thick from the bottom to the top of the connecting arches. The inner wall is carried up plumb with off-sets; the lower section six feet thick; the middle section five feet thick. The span between the exterior and interior walls, at 41 feet below the top, is 14 feet, or 24 feet from the outside of exterior to the inside of interior walls, and the span between them at the spring of the connecting arches, in consequence of the bevel of the exterior wall, is reduced to 9 feet and 9 inches; and from outside of exterior to inside of interior walls, 17.75 feet. The cross-walls are four fect thick at the bottom, and have an off-set of six inches on each side, at eight feet below the spring-line of the connecting arches, and have openings at a suitable level near the bottom, to allow the construction of drains, and to permit persons to pass in and examine the work.

On each corner of the reservoir, pilasters 40 feet in width are raised, projecting four feet from the main walls, and in the centre on the streets and on the 5th avenue, are pilasters 60 feet wide, and projecting six feet. The pilaster in the centre on the 5th avenue.

rises seven feet above the main wall, and all the others four above. Doors are placed in the central pilasters on 40th and 42d streets, which give access to the pipe-chambers. In the central pilaster an entrance is made by a door to a stairway that leads to the top of the walls. On the outside walls is an Egyptian cornice, which accords with the general style of the work. Inside of the walls. of masonry, a thoroughly-puddled embankment of suitable earth is formed, 58 feet wide at the line of the reservoir bottom, and sloping on the inside face 1 to 1 per 24 feet high, and making, with the walls on top, a width of 17 feet; the face of the banks is lined with a course of rubble hydraulic masonry 15 inches. thick, and coped with dressing-stone. The bottom is an impervious hardpan, on which two feet of puddled earth is laid, and this covered by 12 inches of hydraulic cement. The reservoir is divided into two divisions by a wall of hydraulic masonry; the wall is 19 feet thick at the bottom, 63 feet at top water-line, and 4 feet at the top. In this wall a waste-weir is placed, with a well of two falls, together 52 feet, from which the waste-water enters a sewer and passes off about one mile to the Hudson. In each division there is a waste-cock to draw the water from the bottom. The reservoir is designed for 36 feet of water, and when full, will stand 115 feet above mean tide. The walls rise four feet above the water-line. An iron railing is to be placed around the walls on the top of the cornice. The capacity of this reservoir is 20,000,000 imperial gallons.

The general declivity of the aqueduct is 0.021 foot per hundred, or a fraction over 131 inches per mile. The Croton reservoir, which has received the name of Croton lake, is available for 500,000,000 imperial gallons of water, above the level that would allow the aqueduct to discharge 35,000,000 gallons per day. The flow of the Croton river is about 27,000,000 of gallons in twenty-four hours, at the lowest stages. The work was commenced in May, 1837, and has been so far completed that the water was admitted into the distributing reservoir on the 4th of July last. The survey, plans, and estimates of the work were made by Professor Douglass, who was succeeded as chief-engineer by John B. Jervis. The aqueduct has been constructed at the expense of the city of New York, under the direction and supervision of commissioners appointed by the governor and senate. The following persons have been commissioners: Stephen

Allen, Walter Bowne, Benjamin M. Brown, Saul Alley, Charles Dusenbury, William M. Fox, Thomas T. Woodruff, and Samuel R. Childs. The present commissioners are Samuel Stevens, John D. Ward, Benjamin Birdsall, and Zebedee Ring. The cost of the work is about twelve millions of dollars.*

In 1823, a place was assigned to the science of civil engineering in the programme of studies at the United States military academy at West Point. This excellent national institution traces its origin to the recommendation of Washington. It was founded in 1802, and having received especial care and attention under the administration of Jefferson, was enlarged in 1812, on the earnest recommendation of Madison. The school consists of two hundred and fifty cadets, divided into four companies, and taught in the field all the duties of the military profession. They are divided, for theoretical instruction, into four classes, and four years are required to complete the entire course of studies. That course includes mathematics, the French language, English composition, rhetoric, geography, topographical drawing, natural and experimental philosophy, chemistry, landscape-drawing, engineering, the science of war, ethics, constitutional law, infantry tactics, artillery, pyrotechny, mineralogy, and geology.†

Although our civil architecture is open to criticism, yet several of our state and municipal edifices furnish evidence of improving taste. The custom-house, the exchange, the university, and the halls of justice, in New York; the exchange, public edifices, and academic structures, in Albany; and the lunatic asylum at Utica, and the state-prison at Auburn-although they exhibit departures from severe canons, are nevertheless believed to be creditable to the enterprise of our citizens. Not much can be said in praise of the monumental branch. Notwithstanding some puerility of detail, when we compare St. Paul's and the old Trinity with more recent structures, we might infer that sacred architecture was declining. Our domestic architecture has improved with the increase of wealth in private life. While we can not now, or ever hereafter, compare with the palaces of individuals who enjoy hereditary wealth and rank in other countries,

*An account of the Croton aqueduct, prepared by J. B. Jervis, chief-engineer, was received from Samuel Stevens, the president of the board of commissioners.

Notes concerning the military academy were received from Col. De Russy, U.S. A.

we may safely claim, that for suitableness to our social state, and for all that can minister to domestic convenience and comfort, the edifices of our citizens are not surpassed in any other community.* Our naval architecture may perhaps justly be regarded as a peculiar triumph of American genius. Our packetships engaged in foreign trade, and especially the steam palaces which float upon the Hudson river, Long Island Sound, and the lakes, combine the elements of strength and beauty with great speed and perfection of internal arrangements. While the civilized world is in the full enjoyment of the advantages of steamnavigation, the people of New York, at least, need not to be reminded of their obligations to her own eminent citizens, Robert Fulton, John Stevens, and Robert R. Livingston. Experiments on steam-navigation were commenced in 1791, by John Stevens, of Hoboken. He invented the first tubular boiler. His first attempts were made with a rotary engine, for which, however, he speedily substituted one of Watts'. With various forms of vessels, and different modifications of propelling apparatus, he impelled boats. In 1797, Chancellor Livingston built a steamboat on the Hudson, and the legislature granted an exclusive privilege of steam navigation, on condition that he should, within a year, produce a vessel impelled by steam at the rate of three miles per hour. Being unable to perform this condition, the privilege failed. Livingston and Stevens united their efforts with those of Nicholas Roosevelt in 1800, but without success. Chancellor Livingston pursued his favorite object in Paris, where he engaged the efforts of Fulton. Fulton, after a trial of various other apparatus for propulsion, decided that the paddle-wheels possessed the greatest advantage. He then planned a mode of attaching wheels to Watts' engine, and, finding the experiment successful in a trial on the Seine, it was determined by him and Livingston to build a large boat upon the Hudson. He then proceeded to England, and personally superintended the construction of a new engine by Watts and Bolton. This engine was received in New York in 1806, and the vessel prepared for it was set in motion in 1807, the legislature having extended the law. During this time Stevens had persevered in his efforts at home, and only three or four days after Fulton's success was

*Notes on Civil Engineering and Architecture were received from Prof. Mahan, of the United States Military Academy of West Point.