Part 7

On the upstream side of the masonry of the dam, an embankment of earth is filled in, extending 275 feet from the masonry at the base, and extending from the masonry with a slope of 1 foot in 5 on the top.

The whole work about the dam possesses great interest, and though it be distant from the city and somewhat difficult of access, will not fail to please those who may take time to visit it. Just above the place where the dam is constructed the River had a bold turn and flowed along at the foot of a steep and rugged bank. A road passed along at the base of this hill leading to a mill which was situated at the turn of the River, before mentioned; a substitute for this road, which was submerged, has been made along the hill side passing on the right of the gate house. Enough of the forest has been cleared away to admit of the construction of the work, but the place still possesses much of its original wildness, and to see such beautiful mechanical work standing against the rude rocks,--to observe what changes have been wrought in the form of this rock to render it subservient to the purposes of the work, makes us feel that there has been a strife there; but it all shows that _art_ has gained the ascendency.

The form which has been adopted for the face of the extension of the overfall is a reversed or double curve which would be easily recognized as _Hogarth’s line of beauty_: the overfall for the original dam has a plane face with a curve at the base.

Walks are formed about the work bordered with grass, giving a neatness and finished appearance to the whole; and every thing in connection seems to indicate that the vicinity of the _Croton Dam_ will be one of the resorts in summer seasons for the citizens of New-York. From the Croton Dam the Aqueduct passes along the left side of the valley of the Croton River until at the mouth of this river it reaches the left bank of the Hudson, which it pursues, keeping at a distance of nearly half a mile from the River, until it arrives at the village of Sing-Sing, which is eight miles from the dam. In the course of this distance the Aqueduct passes through four tunnels and encounters many valleys and ravines where high foundation walls were required, and culverts for the passage of the streams.

At the village of Sing-Sing there are two Aqueduct bridges; one over a public road-way, and the other over the Sing-Sing Kill. These bridges and the adjacent work form a very interesting point on the line of Aqueduct.

Plate XII. is a view of the Aqueduct at this place: at the left of the picture may be seen the bridge over the road, and on the right that over the Kill. The bridge over the road has a span of 20 feet, and the direction of the road-way being not at right angles with the line of Aqueduct required the arch to be built askew; the arch lies in the direction of the road-way, having the ends in planes parallel with the direction of the Aqueduct. This bridge is worthy of notice, but public attention is more generally directed to the larger one: _that_ has an arch of 88 feet span and a rise of 33 feet; the form of the arch is elliptical, being a compound curve drawn from five different centres, or radius points. The Kill, or valley over which this arch stands, is a deep narrow gorge worn by a small stream which empties into the Hudson River.

The bottom of the ravine is about 70 feet below the soffit or under side of the arch. Plate XIII. is another view of the large arch taken from the bottom of the valley near it, and shows the bridge which has been constructed for a public road passing under it, and the mill near by.

This arch presents a singularly bold appearance, vaulting over the roadway and rising high up above the old mill, and what adds much to this boldness, is the narrowness of the arch, or small distance from one end of it to the other; being only 23⅓ feet long at the springing line while the span is nearly four times this length. The length of the arch diminishes towards the crown, the ends being in planes not vertical, but inclining towards each other at the top. Each end has a batter or inclination of one twenty fourth of its height, or half an inch to the foot. The arch is built of granite, is 3 feet thick at the crown and 4 feet at the spring or base. The abutments have a foundation of solid rock which was excavated in proper form to give them firm footing. The whole structure presents a degree of stability which seems to defy the effects of time. The Aqueduct has a cast iron lining over this bridge (as it has over all of this character): it is formed of plates five eighths of an inch thick, put together with screw-bolts and nuts and the joints closely filled with iron cement. This lining is within the brick work of the bottom and sides of the channel-way, having four inches of brick outside of it and four inside. The object of it is to prevent any water dripping through the work, lest by any means it should fill the exterior masonry of the bridge with moisture and thus render it liable to injury from frost. Other precautions are taken in forming the masonry about the channel-way, to prevent this exuding, and the whole plan of the work shows foresight and precaution worthy of the highest praise.

From the Sing-Sing Kill the Aqueduct pursues a course along the east bank of the Hudson and the first work of peculiar interest is the Aqueduct bridge over the road from Tarrytown to Sing-Sing; before it reaches this place it passes through three tunnels, over high foundation walls, and encounters deep excavations.

Plate XIV. is a view of this bridge: it is eleven and a quarter miles from the dam. The arch is 20 feet span and has a versed sine or rise of 5 feet. From this the Aqueduct passes on, encounters one tunnel, and reaches the valley of Mill River, twelve miles and three quarters from the dam. This River runs through Sleepy Hollow and enters the Hudson about a mile and a half above Tarrytown. The stream is 72 feet below the bottom of the Aqueduct, and the valley being of considerable width required a very heavy foundation wall.

Plate XV. is a view of the _Mill River Culvert_: it is 25 feet span and 172 feet long. It is about half a mile east of the road leading from Tarrytown to Sing-Sing, and to follow the course of the stream which passes through it, it is three quarters of a mile to the _Old Dutch Church_, near Tarrytown, which is well known, and familiar to every one who has read Irving’s “Legend of Sleepy Hollow.”

There is much of the wildness and beauty of nature about this place; the woods are standing close upon the work,--the stream which passes through the culvert displays its whitened crests as it tears along over the rocky bed, and utters its music until it is lost in the depth of the forest. The wild vines will soon climb the walls and cover them; vegetation will gather over the work until _nature_ and _art_ be harmoniously _wedded_.

From Mill River the Aqueduct passes the village of Tarrytown and through one tunnel and over several depressions and streams, reaching Jewell’s Brook which is seventeen and a half miles from the dam. This stream enters the Hudson River about two miles below Tarrytown. The distance from the mouth of the stream to the line of Aqueduct is only a quarter of a mile.

Plate XVI. is a view of the work at Jewell’s Brook. The culvert for the stream is 6 feet span and 148 feet long. The larger culvert for a private road is 14 feet span and 141 feet long. The wall which supports the Aqueduct at this valley is 50 feet high.

In this case, as in many others, the slope wall which covers the face of the embankment has an arch turned in it over the top of the culverts: the object of this is to prevent the direct pressure of the wall upon the top of the parapet wall, as it would tend to displace the coping or injure the parapet itself.

After crossing Jewell’s Brook the Aqueduct passes along the bank of the Hudson through the village of Dobb’s Ferry, where there is a tunnel and a valley requiring a culvert, and continues from this place to the village of Hastings, where there is an Aqueduct bridge over a rail-road which is used for transporting marble from the quarry near by, to the landing on the Hudson River.

Plate XVII. is a view of this bridge and the view under the arch shows the face of the quarry which is near the work; the landing at the river is near by, giving a very rapid descent from the quarry. The arch has a span of 16 feet and a rise of 1½ foot. This bridge is twenty-one miles from the dam.

From Hastings the Aqueduct continues along the bank of the Hudson until it reaches the village of Yonkers where it leaves the valley of the Hudson, and passing through a tunnel of considerable length reaches the valley of Saw-Mill River. At the crossing of this valley there is a culvert of 20 feet span for a public road to pass under the Aqueduct, and one having two arches each 25 feet span for the river.

Plate XVIII. is a view of the work at Saw Mill River.

The water is set back at this place by a dam for a mill a short distance below, giving the stream an appearance of more magnitude than it really possesses. This point is 25 miles from the dam. The wall which supports the Aqueduct over this valley is 40 feet high.

From Saw-Mill River the Aqueduct passing through one tunnel soon reaches Tibbit’s Brook, which it crosses by means of a foundation wall about 30 feet high and a culvert of 6 feet span, and continues along the south side of the valley of this brook, thence to the Harlem River which it crosses at one mile from McComb’s Dam. This crossing is thirty-three miles from the Croton Dam, and about ten miles from the City-Hall.

The distance across this valley is about a quarter of a mile, and the surface of the River is 120 feet below the bottom of the Aqueduct.

In all the examinations which were made with a view of bringing water from Westchester County, the crossing of this River, or _arm of the sea_, was regarded as the most formidable work that would be encountered; various plans were proposed, and in presenting these plans the project was such as to call into requisition much talent and skill.

An Aqueduct Bridge built of stone, having arches resting upon piers and abutments, was proposed so as to continue the Aqueduct across with its regular inclination.

An Inverted Syphon of iron pipes was proposed; the pipes to descend to a level near the surface of the River, and passing along upon a stone embankment rise again and connect with the Aqueduct: in this stone embankment an arch was to be built of sufficient dimensions to allow free passage of the water of the River.

Another plan was proposed which, though novel in its application to such purpose, was worthy of consideration: this was to build a Suspension Bridge of wire cables reaching across the valley, supported at intervals upon suitable stone piers. This, maintaining the regular inclination of the Aqueduct, would support iron pipes. The design was a bold one, yet instances where such bridges have been constructed for road-ways afford examples of the feasibility and permanency of the structures, and prove that the application of that principle for this purpose was not a visionary project.

The plan which was adopted as the most suitable under all the considerations of economy and security to the work, was a _Low Bridge_ to support an inverted syphon of iron pipes; and the design of it was as follows: adjacent to the southern shore of the river there was to be constructed an arch for the channel of the river, of 80 feet span and springing from abutments 10 feet above high water level; this would form a passage of 80 feet wide, and the height from high water level to the under side of the arch at the crown would be 50 feet: south of this arch followed three other arches on the slope of the rocky hill, of 35, 30, and 25 feet span: south of these arches a foundation wall was designed to continue the plane of inclination to the level of the Aqueduct. From the large arch to the northern shore of the river an embankment of stone was designed for the support of the pipes, and from this wall the table land on the northern shore and the slope of the northern side of the valley, would be excavated to a form to give the proper position to the pipes descending from the Aqueduct. The lowest level of the top of this stone embankment was designed to be 4 feet above flood tide. Suitable parapet walls were designed to be built along the sides of the embankment to sustain a covering of earth over the pipes. With the form which was given to this _inverted syphon_, four pipes, each of 3 feet interior diameter, were found to give a discharge of water equal to that of the Aqueduct of masonry on the established inclination.

In accordance with this plan of the _Low Bridge_ the work for crossing the River was put under contract and some progress made in its execution, when a law was passed by the Legislature of the State requiring, instead of this, a structure, the arches of which should be (over the channel of the river) at least 80 feet span and having a distance of 100 feet from the level of high water to the under side of the crown; or to go under the channel of the river by a structure which should not rise above the bed, and that would leave the present channel unobstructed. At this time when the work was going on vigorously, they were compelled to abandon the plan which had been adopted, and devise one which would comply with the requirements of the law of the Legislature. A comparison was instituted between the plan of a tunnel under the bed of the river and that of a bridge of masonry at the required height above the river.

The tunnel would be at least 300 feet long and the top of the masonry forming it, would be 18 feet below high water level. In this tunnel the iron pipes would pass under the River and would be protected from the salt water.

An estimate of the cost of crossing by means of each plan was made, and the result was in favor of the tunnel under the bed of the River; but from the imperfect knowledge which could at best be obtained of the formation of the bed, there was great uncertainty in the estimate of the cost of the tunnel and the time that would be required for its completion. The history of the progress of work in the tunnel under the Thames at London warned them of the difficulties of such a work and the uncertainty of arriving at a proper estimate of the cost.

In the alternative to which they were driven by the Act of the Legislature, the plan of an Aqueduct bridge of masonry was adopted as the proper one for crossing the River; but in establishing its altitude they complied _only_ with the requisitions of the law, and made the soffit or under side of the arches at the crown, 100 feet above common high water level. This would not carry the work up to the level of the Aqueduct, and would render it necessary to connect the Aqueduct on each side of the valley by iron pipes which would descend to the level of the bridge and crossing it rise again to the masonry channel-way. The plans which were before spoken of for a bridge of masonry across this valley, contemplated a structure which would maintain the regular inclination of the Aqueduct; and the channel-way would have been formed of masonry having a cast iron lining; but a more full consideration of the subject suggested the propriety of using iron pipes over the bridge, even if it had been carried up to the grade plane of the Aqueduct: when the use of iron pipes was determined upon, then considerations of economy induced them to build the work _only_ high enough to comply with the requirements of the law.

The plan which has been adopted for building an Aqueduct bridge across this valley is as follows: on the south shore of the river there is one arch of 50 feet span, across the river there are eight arches, each of 80 feet span, and on the north shore there are six arches each of 50 feet span; making a range of fifteen arches. From the extremes of this range of arches, a foundation wall of dry stone work connects with the Aqueduct.

Two of the piers in the river have a rock foundation and the foundations for those where rock is not obtained is formed by driving piles which are placed 2½ feet from centre to centre, and the spaces between filled with concrete to a depth of 3 feet below the top of them.

Plate XIX. is a view of this bridge, which, when completed, will be the most interesting work on the whole line of Aqueduct, and in its appearance will rival the grandeur of similar works of the Ancient Romans. The height from the foundations in the river, to the top of the work is 150 feet; the width across the top is 21 feet. The pipes when laid upon the bridge will be covered with earth to protect them from frost. The distance between the extremes of the pipes when laid across the bridge will be 1377⅓ feet. For a distance of 18 feet at each end of the pipes there is an inclination and the remainder of the distance across, which is 1341⅓ feet, they are level.

The bottom of the interior of the pipes on the level part, is 12-8/10 feet below the bottom of water way of the Aqueduct on the north side, and 10-5/10 below that on the south side of the valley.

In the progress of excavating in one of the coffer dams in the channel of the river a portion of a sunken vessel was found within the enclosure; it had the appearance of great age. Tradition among the inhabitants of the vicinity says that at an early period of the Revolutionary war a vessel was scuttled and sunk in that part of the river.

To a mind fond of antiquarian researches and accustomed to invest objects of such a nature with associations of the past, this ancient wreck would furnish a fruitful theme. We are now laying the foundation of a magnificent work: at the day when this vessel was sunk the American people were laying the foundation of a new form of government composed of principles which should support a fabric of enduring strength and beauty. We are now building a work which will stand as a monument of the genius and enterprise of the age, but it may be regarded among the fruits of that civil and religious liberty which has been reared upon the foundations formed by the people of that day.

The water is now conveyed across this valley by an iron pipe of 3 feet interior diameter. In the progress of preparing foundations for the piers of the bridge, an embankment has been formed across the River and the pipe leaving the Aqueduct on the north side of the valley follows down the slope of the hill, and crossing over the River upon this embankment, ascends on the south side again to the Aqueduct. At the bottom or lowest point in this pipe, a branch pipe of 1 foot diameter has been connected, extending a distance of 80 feet from it at right angles and horizontally: the end of this pipe is turned upwards to form a jet, and iron plates are fastened upon it giving any form that may be desired to the water issuing. The level of this branch pipe is about 120 feet below the bottom of the Aqueduct on the north side of the valley; affording an opportunity for a beautiful _jet d’eau_;--such an one as cannot be obtained at the fountains in the city. From an orifice of seven inches diameter the column of water rises to a height of 115 feet when there is only a depth of 2 feet of water in the Aqueduct.

To those who had watched over the work during its construction and looked for its successful operation, this was peculiarly gratifying. To see the water leap from this opening and rise upwards with such force and beauty, occasioned pleasing emotions and gave proof that the design and construction of the work were alike faultless, and that all the fondest hopes of its projectors would be realized.

The scenery around this fountain added much to its beauty; there it stood,--a whitened column rising from the river, erect, or shifting its form, or waving like a forest tree as the winds swayed it, with the rainbow tints resting upon its spray, while on either side the wooded hills arose to rival its height: all around was of _nature_; no marble basin,--no allegorical figures, wrought with exquisite touches of _art_ to lure the eye, but a fountain where nature had adorned the place with the grandeur and beauty of her rude hills and mountain scenery.

Plate XX. is a distant view of the jet at Harlem River.

From Harlem River the Aqueduct passes along the south bank of the River for a short distance where it rests in the side of the rocky hill, and continues over an uneven surface encountering two tunnels before it reaches Manhattan Valley, which is about 35 miles from the Croton dam. This valley is four fifths of a mile wide where the Aqueduct meets it, and the depression is 102 feet below the plane of Aqueduct grade.

Here was an opportunity for constructing a work of architectural beauty and boldness by building up with arcades of arches, one line above another, and thus maintain the regular inclination of the Aqueduct; but considerations of economy forbade it. Where the Aqueduct reaches the north side of the valley, a gate chamber is formed, and from this, two pipes of 3 feet interior diameter descend to the bottom of the valley and ascend on the south side to another gate chamber where they connect with the Aqueduct again. Provision is made for four pipes of 3 feet diameter, but at present only two are laid which answer the demands of the city at this time. At the bottom of the valley waste cocks are provided which discharge into a sewer leading to the Hudson River, a distance of half a mile.

The lowest point in the pipes is 102 feet below the bottom of the water way of the Aqueduct on the north side of the valley.

From Manhattan Valley the Aqueduct passes through a tunnel, and following its course the next work of interest is at Clendinning Valley, which is thirty-seven miles from the Croton Dam. This valley is 1900 feet across, and the Aqueduct is supported upon a foundation wall of dry stone work having the face laid in mortar, except over three streets where bridges are built, having an arch of 30 feet span for the carriage-way and one on each side of 10½ feet span for the side walks. These bridges are over 98th, 99th, and 100th streets.

Plate XXI. is a view of a portion of the work at Clendinning Valley showing the three bridges; and comprises a length of about 700 feet.

The greatest height from the foundation to the top of the work is 50 feet, and the width at the bottom of the Aqueduct is 30 feet. Parapet walls are built on the sides of the wall above the bottom of the Aqueduct to support a covering of earth over it.

Plate XXII. is an enlarged view of one of the bridges and a portion of the foundation wall and Aqueduct adjacent to it. The Aqueduct has a cast iron lining over the bridges like that described at the Sing Sing Kill.