"The Pneumatic Tunnel Under Broadway" (1870)

Scientific American · March 5, 1870

We give this week illustrations of this remarkable work, which, with a brief description of the details of construction and mode of operation, will give the general reader a good understanding of the nature of this mode of transit. Having fully set forth the benefits to be derived from it in a previous article, we shall confine ourselves at present entirely to a description of the work and a brief history of the origin and progress of transit by means of air inclosed in tubes.

The engravings give an excellent idea of the various parts and appliances. The tunnel is eight feet in diameter in the clear. It is lined with masonry (brick-work) laid up in water cement. A plan of a small portion of it is shown in Fig. 1, which includes the present terminus and passenger station at the corner of Broadway and Warren street, and shows the position of machinery, etc. This will be at once understood upon inspection, and we therefore pass to the...

Fig 1.

Mode of Excavation

This is shown in Fig. 2 [missing], which represents in section the tunneling machine or shield, designed by Mr. A. E. Beach, of the SCIENTIFIC AMERICAN. The body of the shield is shown at A, and is simply a short tube of timberwork, backed by a heavy wrought iron ring, against which the hydraulic rams, D, act to advance the entire machine. The front part of the shield is a heavy chilled iron ring, B, brought to a cutting edge, and crossed on the interior by shelves, C, also sharpened. Bearing blocks, E, of timber, are placed against the masonry, as shown, on which the rams press when the shield is advanced. F is the pump from which the water is carried to the rams by the pipes G. H is a hood of thin sheet steel within which the masonry is built, in rings of 16 inches length, the bricks interlocked.

The operation of this machine is as follows: The pump is worked by one man, and the rams press with a force of 126 tons against the end of the masonry. This forces the cutting edge and the shelves into the earth to a distance corresponding to the length of stroke in hydraulic cylinders and the earth being removed the masonry is again advanced, and so on step by step.

Whenever it is desired to alter the course of the shield, it is done by turning cocks in the pipes which lead from the pumps to the rams, on that side which is not being advanced. The rams then acting upon the opposite side advance it, thus changing the course of the shield. In this way the machine may be guided with the utmost exactness.

The soil through which the tunnel is advancing is of a loose sandy character. Stones are, however, occasionally met with, and of course must be drilled and split out. The hydraulic rams were finished by E. Lyon, 470 Grand Street, New York. We shall refer to them again.

The method of testing the position at night is shown in Fig. 3. [missing] This is done by driving up from the center of the tunnel a tube in sections until it reaches the surface, by which the position of the shield is accurately determined. It is generally done at night because the street is then vacant.

A Way Station

... is shown in Fig. 4. It will be seen that these stations are not to be damp and dimly lighted cellars, but commodious, airy, and comfortable apartments, wherein passengers may await the arrival of a car with as little inconvenience as they could in the best steam railway stations, and without any of the annoyances that attend the waiting for street cars at street corners.

Fig. 4

The Tunnel and Waiting Station

The portal of the tunnel, shown in Fig. 5, is a massive ornamental structure, of circular form, nine feet in diameter, its bed twenty-one and a half feet below the surface of Broadway. The mouth of the tunnel opens directly into a large underground apartment, one hundred and twenty feet in length, fitted up in good style, for the purposes of a waiting and reception station. This apartment is lighted from the pavement, and occupies the entire space under the Warren street sidewalk.

Fig. 5

The Pneumatic Car

Fig. 6 is a sketch of the interior of the passenger car used in the present tunnel. It is of circular form, richly upholstered, and very comfortable, with seats for eighteen persons. Its interior hight is greater than the cars of the London underground railways. When the pneumatic tunnel is further extended, luxurious cars, 100 feet in length, will be used. The car is brilliantly illuminated by means of a single zircon light.

Fig. 6

The Mode of Propulsion

is one of the most simple things imaginable. Air is forced into the tunnel by a gigantic blowing engine made by P. H. & F. M. Roots, of Connersville, Ind., a section of which is shown in Fig. 7. [missing] This blower is actuated by a steam engine of 100-horse power, and is calculated to deliver when worked at maximum speed, a volume of 100,000 cubic feet of air per minute. A pressure of one fourth of one pound to the square inch would be an aggregate of three-fourths of a tun on the end of the car, far more than required for propulsion.

The blowing engine is positive in its action, pressing the air into the tunnel in the direction shown by the arrows on the ground plan, Fig. 1. When the air current is reversed a partial vacuum is produced in the tunnel, and the pressure of the atmosphere then propels the car in an opposite direction.

The Scope of the Work

The tunnel will when completed, extend from the Battery to the Harlem river.

The tunnel starts from the east end of the reception room, corner of Warren street and Broadway, and extends on a curve to the center of Broadway, thence in a straight line down to a point a little beyond Murray street, where the shield, or tunneling machine now rests. The excavations have been temporarily suspended, for the purpose of affording the press and public an opportunity to examine the works, and witness the operations of the machinery. Mr. Joseph Dixon is the superintendent of the works.

Sketch of the History of the System of Pneumatic Transit

In 1824, John Vallance took out a patent in England for a method of propelling carriages through tubes by atmospheric pressure, and in 1826 he had a car running on this plan. This attempt was succeeded by similar efforts by Messrs. Medhurst and Pinkus. The plan adopted by these gentlemen was the propulsion of the cars by means of a piston running in a slotted tube; an arm projecting through the slot, forming the point of attachment for the cars, and an endless band closing the slot both before and after the arm as shown in Figs. 8 and 9. [missing] The air was in this method exhausted from the tube in front of the piston. This propulsion of cars was successfully performed in this way, but the system is not at present in use.

Vallance's system was again put in operation in 1861, by T. W. Rammell, in London, on a small scale, for carrying letters and packages, where pneumatic tubes, 2 1/2 miles long, and 3 feet in width, have been operated with success for the past seven years.

In 1864 a large tunnel for passenger cars was erected at Sydenham, 1/4 of a mile long, and thousands of passengers were transported. This resulted in the incorporation of the Waterton and Whitehall Railway, which is to extend from Charing Cross under the Thames to the Southwestern Railway. It is not yet completed.

Opening of the Broadway Tunnel to the Public

The doors of the Beach Pneumatic Transit Company were thrown open to the public for the first time on the 26th, when an "Under Broadway Reception" was given, by special invitation to the State authorities, city officials, and members of the press. All the prominent personages of the city and State were present, and the inspection of the works gave the greatest satisfaction. The various daily newspapers have published long accounts of the event, which has produced quite a novel sensation in the metropolis.

The New York Herald says "it was virtually the opening day of the first underground railway in America."

The New York Times says: "Certainly the most novel, if not the most successful, enterprise that New York has seen for many a day is the pneumatic tunnel under Broadway. A myth, or a humbug, it has hitherto been called by everybody who has been excluded from its interior; but hereafter the incredulous public can have the opportunity of examining the undertaking and judging of its merits.

"Yesterday the tunnel was thrown open to the inspection of visitors for the first time and it must be said that every one of them came away surprised and gratified. Such as expected to find a dismal cavernous retreat under Broadway, opened their eyes at the elegant reception room, the light, airy tunnel, and the general appearance of taste and comfort in all the apartments; and those who entered to pick out some scientific flaw in the project, were silenced by the completeness of the machinery, the solidity of the work, and the safety of the running apparatus."

The Evening Mail says: "The problem of tunneling Broadway has been solved. There is no mistake about it. Even as we write, a comfortable passenger car is running smoothly and safely between Warren and Murray streets, demonstrating, beyond contradiction, that it is only a question of time and money to give us rapid and comfortable transportation from the Battery to Harlem river."

The company has temporarily suspended operations on the tunnel in order to give the public an opportunity to examine their works, which are now open for inspection. The entrance is at 260 Broadway, corner Warren St., directly opposite the City Hall. The ladies of the Union Home for the Orphans of Soldiers and Sailors, a most deserving charity, are in possession of the doors, and receive the proceeds of the admission fee, 25 cents.