. The tunnel for City & South London Railway was the first railway tunnel to be excavated using a tunneling shield rather than the “cut and cover” method used elsewhere. The shield was designed by South African engineer James Henry Greathead. As we can see in Figure 24 and Figure 25, it was cylindrical and had steel blades that were forced into the soil by hydraulic rams operating at a pressure of 1575 tonnes per square meter (2240 psi)”  A completed section of tunnel is shown in Figure 26. Note the bolted together cast iron tunnel ring segments.
We end with this paper with the Greathead shield, one of the first of new pioneering tunnel construction technologies, methodologies and materials that would depart from tunneling methods and materials used since antiquity. These new technologies would facilitate the construction urban rail systems in New York, London, and in cities throughout the world, in the late 19th and early 20th centuries. Much can be written regarding the subway innovations that happened during this period. We will cover these in detail in a subsequent paper.
Figure 24. Illustration of the “Beach/Greathead Shield”  .
Figure 25. Illustration of picture of the “Beach/Greathead Shield”  .
Figure 26. Battery powered electric locomotive operating in first deep tube line ever built (Note: bolted together cast iron ring segments comprising the tunnel)   .
This paper traces the evolution of tunnel engineering from Ancient Mesopotamia and the Middle East though Greece and Rome. In the 19th century, New York, ancient roman tunneling technology was rediscovered and re-utilized for aqueducts like the Croton. Moreover, the Roman style of vaulted arch tunnel, which they utilized for pathways and roads (the Cryptoporticus), was repurposed in the 19th century Brooklyn and London for industrial age transportation applications. The first subway tunnels were essentially Cryptoporticus with railroad tracks.
In 1844, the world’s first Subway (aka. Tube, Metro, etc.) tunnel opened in Brooklyn. In many regards, the Atlantic Ave. Tunnel in Brooklyn, and the North Metropolitan Railway tunnel (the first London Tube tunnel) were enlarged versions of Roman Tunnels.
This emulation of the Romans in the first Subway tunnels made sense. When you seek to build something that has never been built before, it is often wise to adopt an architectural solution and structural engineering system from something similar that has withstood the ravages of time. In this paper, we sought to elucidate the engineer principles and mathematical formulas that these 19th century engineers utilized for vaulted arched aqueducts and subway tunnels.
An interesting side-note is that in addition to railway tunnels, the Romans were also emulated through the adoption of the Standard gauge railroad track, which is used throughout the NYC subway system. Moreover, Standard gauge is the most commonly used gauge (spacing between track) used by railroads throughout the contemporary world  .
1“First recorded in 1820-30; sub- + way1”  .
2In addition to the term subway’s most prevalent use in the NY area, as a label we affix to our urban rail transit system, the term “subway” can also refer to any underground passageway, i.e., things such as an underground: pipe gallery, utility area or water conduit. For example, in Manhattan, New York “The Empire City Subway” is not a railway―it is underground vaulting built to contain telephone company cables  .
3“The oldest [written] reference concerning the existence of a drainage system known today so far has been discovered on an older sealing inscription. It was referred to as the construction of a palace and the drainage system of a warehouse. Other information concerning drainage systems in Mesopotamian cities is much younger.” 
4Most dimensions in this paper, and the historical sources cited, are in feet and inches. However, all of Merckel’s measurements are in Meters (1 Meter = 3.28 feet). Further, his particular use of a “comma” when citing dimensions, is equivalent to our decimal point.
5“The brick is quadrangular but not wedge-shaped. The central space… is filled up with brick, laid down in linear length.”
6Cut and cover construction refers to trench excavation, then tunnel construction, then road restoration. This technique will be detailed later in this paper.
7“The exact survey of the Roman sewer network is due to the Italian Engineer Pietro. Due to him, the Cloaca Maxima consists of big Gabine ashlars stones with the following measurements: Length: 2, 50 meters, Height: 0, 80 meters, width: 1, 00 meters. The stones had been connected without grout and mortar. The walls consist of 3 - 4 ashlars layers. A semi-circular shaped arch is based upon them. This barrel vault has 7 to 9 ashlars layers formed by accurately arranged key stones. The river bed is paved with polygonal lava stones. The figures nos. 170 - 172 are illuminating the cross section resp. The longitudinal section of the Cloaca segment (up to the Forum Augustum) that was discovered in 1889. Figure No. 173 shows the cross section of Point No. 2 from the fig. No. 169 site map. Here, as it can be seen in figure No. 173, only two original ashlars stones still exist. Above them, there is a semi-circular vault based upon brick layers. The width of the channel is variable, depending upon the hydraulic gradient conditions. Towards the estuary mouth, the cross section widens. This is an appropriate constellation because the quantity of water that has to be drained is also increasing. The air shafts in fig. 176 & 178 are from a later date. Just after the Cloaca has passed the Janus quadrifons, the same covering vault of key stones ends into a perpendicular front (fig. 177). The adjacent 39 meters show a brick vault. Fig. 179 reproduces the longitudinal section of the Cloaca; fig. 180 is the view of the sewer at Point No. 10.” 
8The work was begun by the first Tarquin [Priscus]; it seems to have been in a degree suspended in the reign of Servius Tullius; and it was completed by Tarquin the Proud [Tarquin Superbus]”  .
9Compare this to Walt Whitman’s writing on the Atlantic Avenue tunnel, some 2300 years later: “A Passage of Solemnity and Darkness” [Whitman, 1963 #1]  .
10Furlongs: “a unit of distance, equal to 220 yards (201 meters) or 1/8 mile (0.2 km)”  .
11Cubit: “an ancient linear unit based on the length of the forearm, from elbow to the tip of the middle finger, usually from 17 to 21 inches (43 to 53 cm).
the other side of a mountain there were mountain streams that could supply the town with a source of water   .
12“In Paris, fragments of the former drainpipes from Roman Times are still preserved upon the isle of Notre Dame. The height of these pipes is 0, 60 meters, the width 0, 50 meters. Remnants of Roman drainpipes have been found in Cologne and in Treves, Germany. Fig. 181 shows the cross section of the channel which was exposed in the neighborhood of Alteburg in Cologne. Interestingly enough are the applied forms of the cross section as well as the embedding of the pipe in blue colored clay.” 
13“Flaminia, Via, an ancient high road of Italy, constructed by C. Flaminius during his censorship (220B.C.). It led from Rome to Ariminum, and was the most important route to the north… Vespasian constructed a new tunnel through the pass of Intercisa, modern Furlo, in A.D. 77”  .
14England was colonized by Rome. Then America was colonized by Britain. Therefore, what would become the United States began as a colony, of a colony of Rome. Therefore, when 19th century engineers were emulating and appropriating Roman vaulted tunnel technology, they were drawing upon what they viewed as the historical roots of their own culture.
15Fires also ravaged NYC during this era, often burning beyond control  . These hard to extinguish fires were partly due to lack of ample pressurized water.
16“It was 1883 before the bacterium Vibrio cholerae was discovered to be the agent causing the gastrointestinal disease. But a turning point in prevention came in 1854, when a London physician, Dr. John Snow, established the connection between contaminated water and cholera. Dr. Snow tested the idea by plotting cholera cases on a map of Soho. This showed that most of the victims drew their water from a public pump on Broad (now Broadwick) Street. An infected baby’s diapers had been dumped into a cesspool near the well. A recent book, ‘Ghost Map’ by Steven Johnson, recounts the discovery.” 
17Brooklyn did not become part of NYC until 1898-a half-century after the Atlantic Avenue Tunnel was built.
18See the following link for contemporary historical documentation:
19The Murray Hill Tunnel in Manhattan, we consider to be the second Subway tunnel, and the London tunnel is the third.
20This station resembles the original LIRR passenger/freight terminal at Atlantic Avenue & Columbia Street. This station was rebuilt (when the tunnel opened) in 1844, a decade prior to the first London Underground line. Also, another passenger/freight terminal station later arose on that same LIRR line at Flatbush & Atlantic Ave in Brooklyn, NY.
 Subway/Define Subway at Dictionary (2017)
 Empire City Subway. (2017) http://www.empirecitysubway.com/
 Sewer History Photos and Graphics (2017)
 How Did King David Conquer Jerusalem (2017)
 Ancient Bible and Book of Mormon Cities Part IV (2017)
 Rome Is Still Technically Using One of the First Sewer Systems in the World (2017)
 The History of Herodotus by Herodotus, 440 BCE (2017)
 Lahanas, M. (2017) The Eupalinos Tunnel of Samos.
 Lacus Curtius · Via Flaminia. (1911) Encyclopaedia Britannica.
 Wilford, J.N. (2008) Cholera Epidemic in New York City in 1832.
 Diamond, R. and Kassel, B. (2009) The Confluence of Four Events That Led to the Creation of the Atlantic Avenue Tunnel. The World’s First Subway.
 Diamond, R. and Kassel, B. (2011) http://brooklynrail.net/proj_aatunnel.html
 NYC Dept. of Highways, and Brooklyn Borough President’s Topographical Bureau. (1916)
 Engineering Timelines—City & South London Railway. (2017)