Chapter XII: Introduction: 203 (2)

Despite the ultimate success of Brunel's Thames Tunnel in 1843, the shield in that case afforded only moderately reliable protection because of the fluidity of the soil driven through, and its tendency to enter the works through the smallest opening in the shield's defense. An English doctor who had made physiological studies of the effects on workmen of the high air pressure within diving bells is said to have recommended to Brunel in 1828 that he introduce an atmosphere of compressed air into the tunnel to exclude the water and support the work face.

This plan was first formally described by Sir Thomas Cochrane (1775-1860) in a British patent of 1830. Conscious of Brunel's problems, he proposed a system of shaft sinking, mining, and tunneling in water-bearing materials by filling the excavated area with air sufficiently above atmospheric pressure to prevent the water from entering and to support the earth. In this, and his description of air locks for passage of men and materials between the atmosphere and the pressurized area, Cochrane fully outlined the essential features of pneumatic excavation as developed since.

In 1839, a French engineer first used the system in sinking a mine shaft through a watery stratum. From then on, the sinking of shafts, and somewhat later the construction of bridge pier foundations, by the pneumatic method became almost commonplace engineering practice in Europe and America. Not until 1879 however, was the system tried in tunneling work, and then, as with the shield ten years earlier, almost simultaneously here and abroad. The first application was in a small river tunnel in Antwerp, only 5 feet in height. This project was successfully completed relying on compressed air alone to support the earth, no shield being used. The importance of the work cannot be considered great due to its lack of scope.

In 1871 Dewitt C. Haskin (1822-1900), a west coast mine and railroad builder, became interested in the pneumatic caissons then being used to found the river piers of Eads' Mississippi River bridge at St. Louis. In apparent total ignorance of the Cochrane patent, he evolved a similar system for tunneling water-bearing media, and in 1873 proposed construction of a tunnel through the silt beneath the Hudson to provide rail connection between New Jersey and New York City.

It would be difficult to imagine a site more in need of such communication. All lines from the south terminated along the west shore of the river and the immense traffic--cars, freight and passengers--was carried across to Manhattan Island by ferry and barge with staggering inconvenience and at enormous cost. A bridge would have been, and still is, almost out of the question due not only to the width of the crossing, but to the flatness of both banks. To provide sufficient navigational clearance (without a drawspan), impracticably long approaches would have been necessary to obtain a permissibly gentle grade.

Haskin formed a tunneling company and began work with the sinking of a shaft in Hoboken on the New Jersey side. In a month it was halted because of an injunction by, curiously, the D L & W Railroad, who feared for their vast investment in terminal and marine facilities. Not until November of 1879 was the injunction lifted and work again commenced. The shaft was completed and an air lock located in one wall from which the tunnel proper was to be carried forward. It was Haskin's plan to use no shield, relying solely on the pressure of compressed air to maintain the work faces and prevent the entry of water. The air was admitted in late December, and the first large-scale pneumatic tunneling operation launched. A single 26-foot, double-track bore was at first undertaken, but a work face of such diameter proved unmanageable and two oval tubes 18 feet high by 16 feet wide were substituted, each to carry a single track. Work went forward with reasonable facility, considering the lack of precedent. A temporary entrance was formed of sheet-iron rings from the air lock down to the tunnel grade, at which point the permanent work of the north tube was started. Immediately behind the excavation at the face, a lining of thin wrought-iron plates was built up, to provide form for the 2-foot, permanent brick lining that followed. The three stages are shown in the model in about their proper relationship of progress. The work is shown passing beneath an old timber-crib bulkhead, used for stabilizing the shoreline.

The silt of the riverbed was about the consistency of putty and under good conditions formed a secure barrier between the excavation and the river above. It was easily excavated, and for removal was mixed with water and blown out through a pipe into the shaft by the higher pressure in the tunnel. About half was left in the bore for removal later. The basic scheme was workable, but in operation an extreme precision was required in regulating the air pressure in the work area.[5] It was soon found that there existed an 11-psi difference between the pressure of water on the top and the bottom of the working face, due to the 22-foot height of the unlined opening. Thus, it was impossible to maintain perfect pneumatic balance of the external pressure over the entire face. It was necessary to strike an average with the result that some water entered at the bottom of the face where the water pressure was greatest, and some air leaked out at the top where the water pressure was below the air pressure. Constant attention was essential: several men did nothing but watch the behavior of the leaks and adjusted the pressure as the ground density changed with advance. Air was supplied by several steam-driven compressors at the surface.

The air lock permitted passage back and forth of men and supplies between the atmosphere and the work area, without disturbing the pressure differential. This principle is demonstrated by an animated model set into the main model, to the left of the shaft (fig. 39). The variation of pressure within the lock chamber to match the atmosphere or the pressurized area, depending on the direction of passage, is clearly shown by simplified valves and gauges, and by the use of light in varying color density. In the Haskin tunnel, 5 to 10 minutes were taken to pass the miners through the lock so as to avoid too abrupt a physiological change.

Despite caution, a blowout occurred in July 1880 due to air leakage not at the face, but around the temporary entrance. One door of the air lock jammed and twenty men drowned, resulting in an inquiry which brought forth much of the distrust with which Haskin was regarded by the engineering profession. His ability and qualifications were subjected to the bitterest attack in and by the technical press. There is some indication that, although the project began with a staff of competent engineers, they were alienated by Haskin in the course of work and at least one withdrew. Haskin's remarks in his own defense indicate that some of the denunciation was undoubtedly justified. And yet, despite this reaction, the fundamental merit of the pneumatic tunneling method had been demonstrated by Haskin and was immediately recognized and freely acknowledged. It was apparent at the same time, however, that air by itself did not provide a sufficiently reliable support for large-area tunnel works in unstable ground, and this remains the only major subaqueous tunnel work driven with air alone.

After the accident, work continued under Haskin until 1882 when funds ran out. About 1600 feet of the north tube and 600 feet of the south tube had been completed. Greathead resumed operations with a shield for a British company in 1889, but exhaustion of funds again caused stoppage in 1891. The tunnel was finally completed in 1904, and is now in use as part of the Hudson and Manhattan rapid-transit system, never providing the sought-after rail link. A splendid document of the Haskin portion of the work is S. D. V. Burr's _Tunneling Under the Hudson River_ published in 1885. It is based entirely upon firsthand material and contains drawings of most of the work, including the auxiliary apparatus. It is interesting to note that electric illumination (arc, not incandescent, lights) and telephones were used, unquestionably the first employment of either in tunnel work.

THE ST. CLAIR TUNNEL

The final model of the soft-ground series reflects, as did the Hoosac Tunnel model for hard-rock tunneling, final emergence into the modern period. Although the St. Clair Tunnel was completed over 70 years ago, it typifies in its method of construction, the basic procedures of subaqueous work in the present day. The Thames Tunnel of Brunel, and Haskin's efforts beneath the Hudson, had clearly shown that by themselves, both the shield and pneumatic systems of driving through fluid ground were defective in practice for tunnels of large area. Note that the earliest successful works by each method had been of very small area, so that the influence of adverse conditions was greatly diminished.

The first man to perceive and seize upon the benefits to be gained by combining the two systems was, most fittingly, Greathead. Although he had projected the technique earlier, in driving the underground City and South London Railway in 1886, he brought together for the first time the three fundamental elements essential for the practical tunneling of soft, water-bearing ground: compressed-air support of the work during construction, the movable shield, and cast-iron, permanent lining. The marriage was a happy one indeed; the limitations of each system were almost perfectly overcome by the qualities of the others.

The conditions prevailing in 1882 at the Sarnia, Ontario, terminal of the Grand Trunk Railway, both operational and physical, were almost precisely the same as those which inspired the undertaking of the Hudson River Tunnel. The heavy traffic at this vital U.S.--Canada rail interchange was ferried inconveniently across the wide St. Clair River, and the bank and river conditions precluded construction of a bridge. A tunnel was projected by the railway in that year, the time when Haskin's tribulations were at their height. Perhaps because of this lack of precedent for a work of such size, nothing was done immediately. In 1884 the railway organized a tunnel company; in 1886 test borings were made in the riverbed and small exploratory drifts were started across from both banks by normal methods of mine timbering. The natural gas, quicksand, and water encountered soon stopped the work.

It was at this time that the railway's president visited Greathead's City and South London workings. The obvious answer to the St. Clair problem lay in the successful conduct of this subway. Joseph Hobson, chief engineer of the Grand Trunk and of the tunnel project, in designing a shield, is said to have searched for drawings of the shields used in the Broadway and Tower Subways of 1868-9, but unable to locate any, he relied to a limited extent on the small drawings of those in Drinker's volume. There is no explanation as to why he did not have drawings of the City and South London shield at that moment in use, unless one considers the rather unlikely possibility that Greathead maintained its design in secrecy.

The Hobson shield followed Greathead's as closely as any other, in having a diaphragm with closable doors, but a modification of Beach's sharpened horizontal shelves was also used. However, these functioned more as working platforms than supports for the earth. The machine was 21-1/2 feet in diameter, an unprecedented size and almost twice that of Greathead's current one. It was driven by 24 hydraulic rams. Throughout the entire preliminary consideration of the project there was a marked sense of caution that amounted to what seems an almost total lack of confidence in success. Commencement of the work from vertical shafts was planned so that if the tunnel itself failed, no expenditure would have been made for approach work. In April 1888, the shafts were started near both riverbanks, but before reaching proper depth the almost fluid clay and silt flowed up faster than it could be excavated and this plan was abandoned. After this second inauspicious start, long open approach cuts were made and the work finally began. The portals were established in the cuts, several thousand feet back from each bank and there the tunneling itself began. The portions under the shore were driven without air. When the banks were reached, brick bulkheads containing air locks were built across the opening and the section beneath the river, about 3,710 feet long, driven under air pressure of 10 to 28 pounds above atmosphere. For most of the way, the clay was firm and there was little air leakage. It was found that horses could not survive in the compressed air, and so mules were used under the river.

In the firm clay, excavation was carried on several feet in front of the shield, as shown in the model (fig. 42). About twelve miners worked at the face. However, in certain strata the clay encountered was so fluid that the shield could be simply driven forward by the rams, causing the muck to flow in at the door openings without excavation. After each advance, the rams were retracted and a ring of iron lining segments built up, as in the Tower Subway. Here, for the first time, an "erector arm" was used for placing the segments, which weighed about half a ton. In all respects, the work advanced with wonderful facility and lack of operational difficulty. Considering the large area, no subaqueous tunnel had ever been driven with such speed. The average monthly progress for the American and Canadian headings totaled 455 feet, and at top efficiency 10 rings or a length of 15.3 feet could be set in a 24-hour day in each heading. The 6,000 feet of tunnel was driven in just a year; the two shields met vis-a-vis in August of 1890.

The transition was complete. The work had been closely followed by the technical journals and the reports of its successful accomplishment thus were brought to the attention of the entire civil engineering profession. As the first major subaqueous tunnel completed in America and the first in the world of a size able to accommodate full-scale rail traffic, the St. Clair Tunnel served to dispel the doubts surrounding such work, and established the pattern for a mode of tunneling which has since changed only in matters of detail.

Of the eight models, only this one was built under the positive guidance of original documents. In the possession of the Canadian National Railways are drawings not only of all elements of the shield and lining, but of much of the auxiliary apparatus used in construction. Such materials rarely survive, and do so in this case only because of the foresight of the railway which, to avoid paying a high profit margin to a private contractor as compensation for the risk and uncertainty involved, carried the contract itself and, therefore, preserved all original drawing records.

While the engineering of tunnels has been comprehensively treated in this paper from the historical standpoint, it is well to still reflect that the advances made in tunneling have not perceptibly removed the elements of uncertainty but have only provided more positive and effective means of countering their forces. Still to be faced are the surprises of hidden streams, geologic faults, shifts of strata, unstable materials, and areas of extreme pressure and temperature.

BIBLIOGRAPHY

AGRICOLA, GEORGIUS. _De re Metallica._ [English transl. H. C. and L.
H. Hoover (_The Mining Magazine_, London, 1912).] Basel: Froben,
1556.

BEACH, ALFRED ELY. _The pneumatic dispatch._ New York: The American
News Company, 1868.

BEAMISH, RICHARD. _A memoir of the life of Sir Marc Isambard
Brunel._ London: Longmans, Green, Longmans and Roberts, 1862.

BURR, S. D. V. _Tunneling under the Hudson River._ New York: John
Wiley and Sons, 1885.

COPPERTHWAITE, WILLIAM CHARLES. _Tunnel shields and the use of
compressed air in subaqueous works._ New York: D. Van Nostrand
Company, 1906.

DRINKER, HENRY STURGESS. _Tunneling, explosive compounds and rock
drills._ New York: John Wiley and Sons, 1878.

LATROBE, BENJAMIN H. Report on the Hoosac Tunnel (Baltimore, October
1, 1862). Pp. 125-139, app. 2, in _Report of the commissioners upon
the Troy and Greenfield Railroad and Hoosac Tunnel_. Boston, 1863.

LAW, HENRY. A memoir of the Thames Tunnel. _Weale's Quarterly Papers
on Engineering_ (London, 1845-46), vol. 3, pp. 1-25 and vol. 5,
pp. 1-86.

The pneumatic tunnel under Broadway, N.Y. _Scientific American_
(March 5, 1870), pp. 154-156.

_Report of the commissioners upon the Troy and Greenfield Railroad
and Hoosac Tunnel to his excellency the governor and the honorable
the executive council of the state of Massachusetts, February 28,
1863._ Boston, 1863.

STORROW, CHARLES S. Report on European tunnels (Boston, November 28,
1862). Pp. 5-122, app. 1, in _Report of the commissioners upon the
Troy and Greenfield Railroad and Hoosac Tunnel...._ Boston, 1863.

The St. Clair Tunnel. _Engineering News_ (in series running October
4 to December 27, 1890).

FOOTNOTES

[1] There are two important secondary techniques for opening
subterranean and subaqueous ways, neither a method truly of
tunneling. One of these, of ancient origin, used mainly in the
construction of shallow subways and utility ways, is the "cut and
cover" system, whereby an open trench is excavated and then roofed
over. The result is, in effect, a tunnel. The concept of the other
method was propounded in the early 19th century but only used
practically in recent years. This is the "trench" method, a sort
of subaqueous equivalent of cut and cover. A trench is dredged in
the bed of a body of water, into which prefabricated sections of
large diameter tube are lowered, in a continuous line. The joints
are then sealed by divers, the trench is backfilled over the tube,
the ends are brought up to dryland portals, the water is pumped
out, and a subterranean passage results. The Chesapeake Bay Bridge
Tunnel (1960-1964) is a recent major work of this character.

[2] In 1952 a successful machine was developed on this plan, with
hardened rollers on a revolving cutting head for disintegrating
the rock. The idea is basically sound, possessing advantages in
certain situations over conventional drilling and blasting
systems.

[3] In 1807 the noted Cornish engineer Trevithick commenced a small
timbered drift beneath the Thames, 5 feet by 3 feet, as an
exploratory passage for a larger vehicular tunnel. Due to the
small frontal area, he was able to successfully probe about 1000
feet, but the river then broke in and halted the work. Mine
tunnels had also reached beneath the Irish Sea and various rivers
in the coal regions of Newcastle, but these were so far below the
surface as to be in perfectly solid ground and can hardly be
considered subaqueous workings.

[4] Unlike the Brunel tunnel, this was driven from both ends
simultaneously, the total overall progress thus being 3 feet per
shift rather than 18 inches. A top speed of 9 feet per day could
be advanced by each shield under ideal conditions.

[5] Ideally, the pressure of air within the work area of a
pneumatically driven tunnel should just balance the hydrostatic
head of the water without, which is a function of its total height
above the opening. If the air pressure is not high enough, water
will, of course, enter, and if very low, there is danger of
complete collapse of the unsupported ground areas. If too high,
the air pressure will overcome that due to the water and the air
will force its way out through the ground, through increasingly
larger openings, until it all rushes out suddenly in a "blowout."
The pressurized atmosphere gone, the water then is able to pour
in through the same opening, flooding the workings.

* * * * *

CONTRIBUTIONS FROM
THE MUSEUM OF HISTORY AND TECHNOLOGY:

PAPER 42

THE "PIONEER": LIGHT PASSENGER LOCOMOTIVE OF 1851
IN THE MUSEUM OF HISTORY AND TECHNOLOGY

_John H. White_

THE CUMBERLAND VALLEY RAILROAD 244

SERVICE HISTORY OF THE "PIONEER" 249

MECHANICAL DESCRIPTION OF THE "PIONEER" 251

FOOTNOTES

_John H. White_

The "PIONEER": LIGHT PASSENGER LOCOMOTIVE of 1851
_In the Museum of History and Technology_

_In the mid-nineteenth century there was a renewed interest in
the light, single-axle locomotives which were proving so very
successful for passenger traffic. These engines were built in
limited number by nearly every well-known maker, and among the
few remaining is the 6-wheel "Pioneer," on display in the Museum
of History and Technology, Smithsonian Institution. This
locomotive is a true representation of a light passenger
locomotive of 1851 and a historic relic of the mid-nineteenth
century._

THE AUTHOR: _John H. White is associate curator of
transportation in the Smithsonian Institution's Museum of
History and Technology._

The "PIONEER" is an unusual locomotive and on first inspection would seem to be imperfect for service on an American railroad of the 1850's. This locomotive has only one pair of driving wheels and no truck, an arrangement which marks it as very different from the highly successful standard 8-wheel engine of this period. All six wheels of the _Pioneer_ are rigidly attached to the frame. It is only half the size of an 8-wheel engine of 1851 and about the same size of the 4--2--0 so common in this country some 20 years earlier. Its general arrangement is that of the rigid English locomotive which had, years earlier, proven unsuitable for use on U.S. railroads.

These objections are more apparent than real, for the _Pioneer_, and other engines of the same design, proved eminently successful when used in the service for which they were built, that of light passenger traffic. The _Pioneer's_ rigid wheelbase is no problem, for when it is compared to that of an 8-wheel engine it is found to be about four feet less; and its small size is no problem when we realize it was not intended for heavy service. Figure 2, a diagram, is a comparison of the _Pioneer_ and a standard 8-wheel locomotive.

Since the service life of the _Pioneer_ was spent on the Cumberland Valley Railroad, a brief account of that line is necessary to an understanding of the service history of this locomotive.

_Exhibits of the "Pioneer"_

The _Pioneer_ has been a historic relic since 1901. In the fall
of that year minor repairs were made to the locomotive so that
it might be used in the sesquicentennial celebration at
Carlisle, Pennsylvania. On October 22, 1901, the engine was
ready for service, but as it neared Carlisle a copper flue
burst. The fire was extinguished and the _Pioneer_ was pushed
into town by another engine. In the twentieth century, the
_Pioneer_ was displayed at the Louisiana Purchase Exposition,
St. Louis, Missouri, in 1904, and at the Wheeling, West
Virginia, semicentennial in 1913. In 1927 it joined many other
historic locomotives at the Baltimore and Ohio Railroad's "Fair
of the Iron Horse" which commemorated the first one hundred
years of that company. From about 1913 to 1925 the _Pioneer_
also appeared a number of times at the Apple-blossom Festival
at Winchester, Virginia. In 1933-1934 it was displayed at the
World's Fair in Chicago, and in 1948 at the Railroad Fair in the
same city. Between 1934 and March 1947 it was exhibited at the
Franklin Institute, Philadelphia, Pennsylvania.

The Cumberland Valley Railroad

The Cumberland Valley Railroad (C.V.R.R.) was chartered on April 2, 1831, to connect the Susquehanna and Potomac Rivers by a railroad through the Cumberland Valley in south-central Pennsylvania. The Cumberland Valley, with its rich farmland and iron-ore deposits, was a natural north-south route long used as a portage between these two rivers. Construction began in 1836, and because of the level valley some 52 miles of line was completed between Harrisburg and Chambersburg by November 16, 1837. In 1860, by way of the Franklin Railroad, the line extended to Hagerstown, Maryland. It was not until 1871 that the Cumberland Valley Railroad reached its projected southern terminus, the Potomac River, by extending to Powells Bend, Maryland. Winchester, Virginia, was entered in 1890 giving the Cumberland Valley Railroad about 165 miles of line. The railroad which had become associated with the Pennsylvania Railroad in 1859, was merged with that company in 1919.

By 1849 the Cumberland Valley Railroad was in poor condition; the strap-rail track was worn out and new locomotives were needed. Captain Daniel Tyler was hired to supervise rebuilding the line with T-rail, and easy grades and curves. Tyler recommended that a young friend of his, Alba F. Smith, be put in charge of modernizing and acquiring new equipment. Smith recommended to the railroad's Board of Managers on June 25, 1851, that "much lighter engines than those now in use may be substituted for the passenger transportation and thereby effect a great saving both in point of fuel and road repairs...."[1] Smith may well have gone on to explain that the road was operating 3- and 4-car passenger trains with a locomotive weighing about 20 tons; the total weight was about 75 tons, equalling the uneconomical deadweight of 1200 pounds per passenger. Since speed was not an important consideration (30 mph being a good average), the use of lighter engines would improve the deadweight-to-passenger ratio and would not result in a slower schedule.

The Board of Managers agreed with Smith's recommendations and instructed him "... to examine the two locomotives lately built by Mr. Wilmarth and now in the [protection?] of Captain Tyler at Norwich and if in his judgment they are adequate to our wants ... have them forwarded to the road."[2] Smith inspected the locomotives not long after this resolution was passed, for they were on the road by the time he made the following report[3] to the Board on September 24, 1851:

In accordance with a resolution passed at the last meeting of
your body relative to the small engines built by Mr. Wilmarth I
proceeded to Norwich to make trial of their capacity--fitness or
suitability to the Passenger transportation of our Road--and
after as thorough a trial as circumstances would admit (being on
another Road than our own) I became satisfied that with some
necessary improvements which would not be expensive (and are now
being made at our shop) the engines would do the business of
our Road not only in a manner satisfactory in point of speed and
certainty but with greater ultimate economy in Expenses than has
before been practised in this Country.

_Columbia_

Hudson River Railroad
Lowell Machine Shop, 1852
Wt. 27-1/2 tons (engine only)
Cyl. 16-1/2 x 22 inches
Wheel diam. 84 inches

_Pioneer_

Cumberland Valley Railroad
Seth Wilmarth, 1851
12-1/2 tons
8-1/2 x 14 inches
54 inches

After making the above trial of the Engines--I stated to your
Hon. President the result of the trial--with my opinion of their
Capacity to carry our passenger trains at the speed required
which was decidedly in favor of the ability of the Engines. He
accordingly agreed that the Engines should at once be forwarded
to the Road in compliance with the Resolution of your Board. I
immediately ordered the Engines shipped at the most favorable
rates. They came to our Road safely in the Condition in which
they were shipped. One of the Engines has been placed on the
Road and I believe performed in such a manner as to convince all
who are able to judge of this ability to perform--although the
maximum duty of the Engines was not performed on account of some
original defects which are now being remedied as I before
stated.

Within ten days the Engine will be able to run regularly with a
train on the Road where in shall be enabled to judge correctly
of their merits.

An accident occurred during the trial of the Small Engine at
Norwich which caused a damage of about $300 in which condition
the Engine came here and is now being repaired--the cost of
which will be presented to your Board hereafter. As to the
fault or blame of parties connected with the accident as also
the question of responsibility for Repairs are questions for
your disposal. I therefore leave the matter until further called
upon.

The Expenses necessarily incurred by the trial of the Engines
and also the Expenses of transporting the same are not included
in the Statement herewith presented, the whole amount of which
will not probably exceed $400.00.

These two locomotives became the Cumberland Valley Railroad's _Pioneer_ (number 13) and _Jenny Lind_ (number 14). While Smith notes that one of the engines was damaged during the inspection trials, Joseph Winters, an employee of the Cumberland Valley who claimed he was accompanying the engine enroute to Chambersburg at the time of their delivery, later recalled that both engines were damaged in transit.[4] According to Winters a train ran into the rear of the _Jenny Lind_, damaging both it and the _Pioneer_, the accident occurring near Middletown, Pennsylvania. The _Jenny Lind_ was repaired at Harrisburg but the _Pioneer_, less seriously damaged, was taken for repairs to the main shops of the Cumberland Valley road at Chambersburg.

While there seems little question that these locomotives were not built as a direct order for the Cumberland Valley Railroad, an article[5] appearing in the _Railroad Advocate_ in 1855 credits their design to Smith. The article speaks of a 2--2--4 built for the Macon and Western Railroad and says in part:

This engine is designed and built very generally upon the ideas,
embodied in some small tank engines designed by A. F. Smith,
Esq., for the Cumberland Valley road. Mr. Smith is a strong
advocate of light engines, and his novel style and proportions
of engines, as built for him a few years since, by Seth
Wilmarth, at Boston, are known to some of our readers. Without
knowing all the circumstances under which these engines are
worked on the Cumberland Valley road, we should not venture to
repeat all that we have heard of their performances, it is
enough to say that they are said to do more, in proportion to
their weight, than any other engines now in use.

The author believes that the _Railroad Advocate's_ claim of Smith's design of the _Pioneer_ has been confused with his design of the _Utility_ (figs. 6, 7). Smith designed this compensating-lever engine to haul trains over the C.V.R.R. bridge at Harrisburg. It was built by Wilmarth in 1854.

According to statements of Smith and the Board of Managers quoted on page 244, the _Pioneer_ and the _Jenny Lind_ were not new when purchased from their maker, Seth Wilmarth. Although of recent manufacture, previous to June 1851, they were apparently doing service on a road in Norwich, Connecticut. It should be mentioned that both Smith and Tyler were formerly associated with the Norwich and Worcester Railroad and they probably learned of these two engines through this former association. It is possible that the engines were purchased from Wilmarth by the Cumberland Valley road, which had bought several other locomotives from Wilmarth in previous years. It was the practice of at least one other New England engine builder, the Taunton Locomotive Works, to manufacture engines on the speculation that a buyer would be found; if no immediate buyers appeared the engine was leased to a local road until a sale was made.[6]

Regarding the _Jenny Lind_ and _Pioneer_, Smith reported[7] to the Board of Managers at their meeting of March 17, 1852:

The small tank engines which were purchased last year ... and
which I spoke in a former report as undergoing at that time some
necessary improvements have since that time been fairly tested
as to their capacity to run our passenger trains and proved to
be equal to the duty.

The improvements proposed to be made have been completed only on
one engine [_Jenny Lind_] which is now running regularly with
passenger trains--the cost of repairs and improvements on this
engine (this being the one accidentally broken on the trial)
amounted to $476.51. The other engine is now in the shop, not
yet ready for service but will be at an early day.

The _Pioneer_ and _Jenny Lind_ achieved such success in action that the president of the road, Frederick Watts, commented on their performance in the annual report of the Cumberland Valley Railroad for 1851. Watts stated that since their passenger trains were rarely more than a baggage car and two coaches, the light locomotives "... have been found to be admirably adapted to our business." The Cumberland Valley Railroad, therefore, added two more locomotives of similar design in the next few years. These engines were the _Boston_ and the _Enterprise_, also built by Wilmarth in 1854-1855.

Watts reported the _Pioneer_ and _Jenny Lind_ cost $7,642. A standard 8-wheel engine cost about $6,500 to $8,000 each during this period. In recent years, the Pennsylvania Railroad has stated the _Pioneer_ cost $6,200 in gold, but is unable to give the source for this information. The author can discount this statement for it does not seem reasonable that a light, cheap engine of the pattern of the _Pioneer_ could cost as much as a machine nearly twice its size.

Service History of the _Pioneer_

After being put in service, the _Pioneer_ continued to perform well and was credited as able to move a 4-car passenger train along smartly at 40 mph.[8] This tranquility was shattered in October 1862 by a raiding party led by Confederate General J. E. B. Stuart which burned the Chambersburg shops of the Cumberland Valley Railroad. The _Pioneer_, _Jenny Lind_, and _Utility_ were partially destroyed. The Cumberland Valley Railroad in its report for 1862 stated:

The Wood-shop, Machine-shop, Black-smith-shop, Engine-house,
Wood-sheds, and Passenger Depot were totally consumed, and with
the Engine-house three second-class Engines were much injured by
the fire, but not so destroyed but that they may be restored to
usefulness.

However, no record can be found of the extent or exact nature of the damage. The shops and a number of cars were burned so it is reasonable to assume that the cab and other wooden parts of the locomotive were damaged. One unverified report in the files of the Pennsylvania Railroad states that part of the roof and brick wall fell on the _Pioneer_ during the fire causing considerable damage. In June 1864 the Chambersburg shops were again burned by the Confederates, but on this occasion the railroad managed to remove all its locomotives before the raid. During the Civil War, the Cumberland Valley Railroad was obliged to operate longer passenger trains to satisfy the enlarged traffic. The _Pioneer_ and its sister single-axle engines were found too light for these trains and were used only on work and special trains. Reference to table 1 will show that the mileage of the _Pioneer_ fell off sharply for the years 1860-1865.

TABLE 1.--YEARLY MILEAGE OF THE PIONEER

(From Annual Reports of the Cumberland Valley Railroad)

_Year_: _Miles_

1852 3,182[a]
1853 20,722[b]
1854 18,087
1855 14,151
1856 20,998
1857 22,779
1858 29,094
1859 29,571
1860 4,824
1861 4,346
1862 ([c])
1863 5,339
1864 224
1865 2,215
1866 20,546
1867 5,709
1868 13,626
1869 1,372
1870 ...
1871 2,102
1872 4,002
1873 3,721
1874 3,466
1875 636
1876 870
1877 406
1878 4,433
1879 ...
1880 8,306
1881 ([d])
---------
Total 244,727[e]

FOOTNOTES TO TABLE 1:

[a] Mileage 1852 for January to September (no record of mileage
recorded in Annual Reports previous to 1852).

[b] 15,000 to 20,000 miles per year was considered very high
mileage for a locomotive of the 1850's.

[c] No mileage reported for any engines due to fire.

[d] Not listed on roster.

[e] The Pennsylvania Railroad claims a total mileage of 255,675.
This may be accounted for by records of mileages for 1862, 1870,
and 1879.

In 1871 the _Pioneer_ was remodeled by A. S. Hull, master mechanic of the railroad. The exact nature of the alterations cannot be determined, as no drawings or photographs of the engine previous to this time are known to exist. In fact, the drawing (fig. 8) prepared by Hull in 1876 to show the engine as remodeled in 1871 is the oldest known illustration of the _Pioneer_. Paul Westhaeffer, a lifelong student of Cumberland Valley R. R. history, states that according to an interview with one of Hull's descendants the only alteration made to the _Pioneer_ during the 1871 "remodeling" was the addition of a handbrake. The road's annual report of 1853 describes the _Pioneer_ as a six-wheel tank engine. The report of 1854 mentions that the _Pioneer_ used link motion. These statements are enough to give substance to the idea that the basic arrangement has survived unaltered and that it has not been extensively rebuilt, as was the _Jenny Lind_ in 1878.

By the 1870's, the _Pioneer_ was too light for the heavier cars then in use and by 1880 it had reached the end of its usefulness for regular service. After nearly thirty years on the road it had run 255,675 miles. Two new passenger locomotives were purchased in 1880 to handle the heavier trains. In 1881 the _Pioneer_ was dropped from the roster, but was used until about 1890 for work trains. After this time it was stored in a shed at Falling Spring, Pennsylvania, near the Chambersburg yards of the C.V.R.R.

Mechanical Description of the _Pioneer_

After the early 1840's the single-axle locomotive, having one pair of driving wheels, was largely superseded by the 8-wheel engine. The desire to operate longer trains and the need for engines of greater traction to overcome the steep grades of American roads called for coupled driving wheels and machines of greater weight than the 4--2--0. After the introduction of the 4--4--0, the single-axle engine received little attention in this country except for light service or such special tasks as inspection or dummy engines.

There was, however, a renewed interest in "singles" in the early 1850's because of W. B. Adams' experiments with light passenger locomotives in England. In 1850 Adams built a light single-axle tank locomotive for the Eastern Counties Railway which proved very economical for light passenger traffic. It was such a success that considerable interest in light locomotives was generated in this country as well as in England. Nearly 100 single-axle locomotives were built in the United States between about 1845-1870. These engines were built by nearly every well-known maker, from Hinkley in Boston to the Vulcan Foundry in San Francisco. Danforth Cooke & Co. of Paterson built a standard pattern 4--2--4 used by many roads. One of these, the _C. P. Huntington_, survives to the present time.

The following paragraphs describe the mechanical details of the _Pioneer_ as it appears on exhibition in the Smithsonian Institution's new Museum of History and Technology.

BOILER

The boiler is the most important and costly part of a steam locomotive, representing one-fourth to one-third of the total cost. A poorly built or designed boiler will produce a poor locomotive no matter how well made the remainder of mechanism. The boiler of the _Pioneer_ is of the wagon-top, crownbar, fire-tube style and is made of a 5/16-inch thick, wrought-iron plate. The barrel is very small, in keeping with the size of the engine, being only 27 inches in diameter. While some readers may believe this to be an extremely early example of a wagon-top boiler, we should remember that most New England builders produced few locomotives with the Bury (dome) boiler and that the chief advocates of this later style were the Philadelphia builders. By the early 1850's the Bury boiler passed out of favor entirely and the wagon top became the standard type of boiler with all builders in this country.

Sixty-three iron tubes, 1-7/8 inches by 85 inches long are used. The original tubes may have been copper or brass since these were easier to keep tight than the less malleable iron tubes. The present tube sheet is of iron but was originally copper. Its thickness cannot be conveniently measured, but it is greater than that of the boiler shell, probably about 1/2 to 5/8 inch. While copper tubes and tube sheets were not much used in this country after about 1870, copper was employed as recently as 1950 by Robert Stephenson & Hawthorns, Ltd., on some small industrial locomotives.

The boiler shell is lagged with wooden tongue-and-groove strips about 2-1/2 inches wide (felt also was used for insulation during this period). The wooden lagging is covered with Russia sheet iron which is held in place and the joints covered by polished brass bands. Russia sheet iron is a planish iron having a lustrous, metallic gray finish.

The steam dome (fig. 18) is located directly over the firebox, inside the cab. It is lagged and jacketed in an identical manner to the boiler. The shell of the dome is of 5/16-inch wrought iron, the top cap is a cast-iron plate which also serves as a manhole cover offering access to the boiler's interior for inspection and repair.

A round plate, 20 inches in diameter, riveted on the forward end of the boiler, just behind the bell stand, was found when the old jacket was removed in May 1963. The size and shape of the hole, which the plate covers, indicate that a steam dome or manhole was located at this point. It is possible that this was the original location of the steam dome since many builders in the early 1850's preferred to mount the dome forward of the firebox. This was done in the belief that there was less danger of priming because the water was less agitated forward of the firebox.

The firebox is as narrow as the boiler shell and fits easily between the frame. It is a deep and narrow box, measuring 27 inches by 28 inches by about 40 inches deep, and is well suited to burning wood. A deep firebox was necessary because a wide, shallow box suitable for coal burning, allowed the fuel to burn so quickly it was difficult to fire the engine effectively. With the deep, narrow firebox, wood was filled up to the level of the fire door. In this way, the fire did not burn so furiously and did not keep ahead of the fireman; at the same time, since it burned so freely, a good fire was always on hand. The _Pioneer_ burned oak and hickory.[14] For the firebox 5/16-inch thick sheet was used, for heavier sheet would have blistered and flaked off because of the intense heat of the fire and the fibrous quality of wrought-iron sheet of the period. Sheet iron was fabricated from many small strips of iron rolled together while hot. These strips were ideally welded into a homogeneous sheet, but in practice it was found the thicker the sheet the less sure the weld.

The fire grates are cast iron and set just a few inches above the bottom of the water space so that the water below the grates remains less turbulent and mud or other impurities in the water settle here. Four bronze mud plugs and a blowoff cock are fitted to the base of the firebox so that the sediment thus collected can be removed (figs. 17, 18).

The front of the boiler is attached to the frame by the smokebox, which is a cylinder, bolted on a light, cast-iron saddle (not part of the cylinder castings nor attached to them, but bolted directly to the top rail of the frame; it may be a hastily made repair put on at the shops of the C.V.R.R.). The rear of the boiler is attached to the frame by two large cast-iron brackets, one on each side of the firebox (fig. 18). These are bolted to the top rail of the frame but the holes in the brackets are undoubtedly slotted, so that they may slide since the boiler will expand about 1/4 inch when heated. In addition to the crown bars, which strengthen the crown sheet, the boiler is further strengthened by stay bolts and braces located in the wagon top over the firebox, where the boiler had been weakened by the large hole necessary for the steam dome. This boiler is a remarkably light, strong, and compact structure.

BOILER FITTINGS

Few boiler fittings are found on the _Pioneer_ and it appears that little was done to update the engine with more modern devices during its many years of service. With the exception of the steam gauge, it has no more boiler fitting than when it left the builder's shop in 1851.

The throttle valve is a simple slide valve and must have been primitive for the time, for the balance-poppet throttle valve was in use in this country previous to 1851. It is located directly below the steam dome even though it was common practice to place the throttle valve at the front of the boiler in the smokebox. Considering the cramped condition inside the smokebox, there would seem to be little space for the addition of the throttle valve; hence its present location. The dry pipe projects up into the steam dome to gather the hottest, driest steam for the cylinders. The inverted, funnel-like cap on the top of the dry pipe is to prevent priming, as drops of water may travel up the sides of the pipe and then to the cylinders, with the possibility of great damage. After the steam enters the throttle valve it passes through the front end of the valve, through the top of the boiler via the dry pipe (fig. 18), through the front tube sheet, and then to the cylinders via the petticoat pipes. The throttle lever is a simple arrangement readily understood from the drawings. It has no latch and the throttle lever is held in any desired setting by the wingnut and quadrant shown in figure 18. The water level in the boiler is indicated by the three brass cocks located on the backhead. No gauge glass is used; they were not employed in this country until the 1870's, although they were commonly used in England at the time the _Pioneer_ was built.

While two safety valves were commonly required, only one was used on the _Pioneer_. The safety valve is located on top of the steam dome. Pressure is exerted on the lever by a spring balance, fixed at the forward end by a knife-blade bearing. The pressure can be adjusted by the thumbscrew on the balance. The graduated scale on the balance gave a general but uncertain indication of the boiler pressure. The valve itself is a poppet held against the face of the valve seat by a second knife blade attached to the lever. The ornamental column forming the stand of the safety valve is cast iron and does much to decorate the interior of the cab. The pipe carrying the escaping steam projects through the cab roof. It is made of copper with a decorative brass band. This entire mechanism was replaced by a modern safety valve for use at the Chicago Railroad Fair (1949). Fortunately, the old valve was preserved and has since been replaced on the engine.

The steam gauge is a later addition, but could have been put on as early as the 1860's, since the most recent patent date that it bears is 1859. It is an Ashcroft gauge having a handsome 4--4--0 locomotive engraved on its silver face.

The steam jet (item 3, fig. 18) is one of the simplest yet most notable boiler fitting of the _Pioneer_, being nothing more than a valve tapped into the base of the steam dome with a line running under the boiler jacket to the smokestack. When the valve is opened a jet of steam goes up the stack, creating a draft useful for starting the fire or enlivening it as necessary. This device was the invention of Alba F. Smith in 1852, according to the eminent 19th-century technical writer and engineer Zerah Colburn.[15]

The two feedwater pumps (fig. 20) are located beneath the cab deck (1, fig. 17). They are cast-iron construction and are driven by an eccentric on the driving-wheel axle (fig. 27). The airchamber or dome (1, fig. 27) imparts a more steady flow of the water to the boiler by equalizing the surges of water from the reciprocating pump plunger. A steam line (3, fig. 18), which heats the pump and prevents freezing in cold weather, is regulated by a valve in the cab (figs. 18, 27). Note that the line on the right side of the cab has been disconnected and plugged.

The eccentric drive for the pumps is unusual, and the author knows of no other American locomotive so equipped. Eastwick and Harrison, it is true, favored an eccentric drive for feed pumps, but they mounted the eccentric on the crankpin of the rear driving wheel and thus produced in effect a half-stroke pump. This was not an unusual arrangement, though a small crank was usually employed in place of the eccentric. The full-stroke crosshead pump with which the _Jenny Lind_ (fig. 22) is equipped, was of course the most common style of feed pump used in this country in the 19th century.

Of all the mechanisms on a 19th-century locomotive, the feed pump was the most troublesome. If an engineer could think of nothing else to complain about, he could usually call attention to a defective pump and not be found a liar. Because of this, injectors were adopted after their introduction in 1860. It is surprising that the _Pioneer_, which was in regular service as late as 1880 and has been under steam many times since for numerous exhibitions, was never fitted with one of these devices. Because its stroke is short and the plunger is in less rapid motion, the present eccentric arrangement is more complex but less prone to disorder than the simpler but faster crosshead pump.

The check valves are placed slightly below the centerline of the boiler (fig. 18). These valves are an unfinished bronze casting and appear to be of a recent pattern, probably dating from the 1901 renovation. At the time the engine was built, it was usual to house these valves in an ornamental spun-brass casing. The smokestack is of the bonnet type commonly used on wood-burning locomotives in this country between about 1845 and 1870. The exhaust steam from the cylinders is directed up the straight stack (shown in phantom in fig. 27) by the blast pipe. This creates a partial vacuum in the smokebox that draws the fire, gases, ash, and smoke through the boiler tubes from the firebox. The force of the exhausting steam blows them out the stack. At the top of the straight stack is a deflecting cone which slows the velocity of the exhaust and changes its direction causing it to go down into the funnel-shaped outer casing of the stack. Here, the heavy embers and cinders are collected and prevented from directly discharging into the countryside as dangerous firebrands. Wire netting is stretched overtop of the deflecting cone to catch the lighter, more volatile embers which may defy the action of the cone. The term "bonnet stack" results from the fact that this netting is similar in shape to a lady's bonnet. The cinders thus accumulated in the stack's hopper could be emptied by opening a plug at the base of the stack.

While the deflecting cone was regarded highly as a spark arrester and used practically to the exclusion of any other arrangement, it had the basic defect of keeping the smoke low and close to the train. This was a great nuisance to passengers, as the low trailing smoke blew into the cars. If the exhaust had been allowed to blast straight out the stack high into the air, most of the sparks would have burned out before touching the ground.

FRAME

The frame of the _Pioneer_ defies an exact classification but it more closely resembles the riveted- or sandwich-type frame than any other (figs. 18, 27). While the simple bar frame enjoyed the greatest popularity in the last century, riveted frames were widely used in this country, particularly by the New England builders between about 1840 and 1860. The riveted frame was fabricated from two plates of iron, about 5/8-inch thick, cut to the shape of the top rail and the pedestal. A bar about 2 inches square was riveted between the two plates. A careful study of photographs of Hinkley and other New England-built engines of the period will reveal this style of construction. The frame of the _Pioneer_ differs from the usual riveted frame in that the top rail is 1-3/4 inches thick by 4-1/8 inches deep and runs the length of the locomotive. The pedestals are made of two 3/8-inch plates flush-riveted to each side of the top rail. The cast-iron shoes which serve as guides for the journal boxes also act as spacers between the pedestal plates.

The bottom rail of the frame is a 1-1/8-inch diameter rod which is forged square at the pedestals and forms the pedestal cap. The frame is further stiffened by two diagonal rods running from the top of each truck-wheel pedestal to the base of the driving-wheel pedestal, forming a truss. Six rods, riveted to the boiler shell and bolted to the frame's top rail, strengthen the frame laterally. Four of these rods can be seen easily as they run from the frame to the middle of the boiler; the other two are riveted to the underside of the boiler. The attachment of these rods to the boiler was an undesirable practice, for the boiler shell was thus subjected to the additional strain of the locomotive's vibrations as it passed over the road. In later years, as locomotives grew in size, this practice was avoided and frames were made sufficiently strong to hold the engine's machinery in line without using the boiler shell.