Details

The monument is situated in the Tillingbourne valley around 4km south east of
Guildford and includes most of the area occupied by the middle works of
Chilworth gunpowder factory. This is the best surviving part of the disused
works and runs for around 1.5km along the valley bottom. The works survive
here in the form of standing buildings and structures, ruins, earthworks and
buried remains. Part of an associated water management system, a packhorse
bridge and the remains of a tramway are also included. In almost continuous
use from 1626 to 1920, the factory complex, which is associated with the
manufacture of gunpowder, brown powder and cordite, underwent many phases of
alteration and redevelopment. Most visible surviving components date to the
1880s-90s. The scheduling occupies two separate areas of protection either
side of Lockner Road.
The Chilworth gunpowder mills were established by the East India Company
in 1626. The early works were powered mainly by water wheels and utilised a
series of surviving, man-made mill races and watercourses which canalised the
east-west flowing Tilling Bourne. In 1636 new proprietors, Collins and
Cordwell, were appointed sole powder makers to King Charles I, and the
Chilworth mills thereby became the only authorised gunpowder factory in the
country. This privileged position lasted until 1641, when the royal monopoly
system was abolished. During the later 17th century, the works were greatly
expanded under Sir Polycarpus Wharton, who took over a 21 year lease in 1677.
The antiquarian John Aubrey visited the site during the 1690s and recorded the
presence of, amongst other components, a sulphur-crushing mill, 18
incorporating mills, a corning mill, and further separating and finishing
houses. Raw materials such as sulphur and saltpetre were brought to the site
by barges up the Thames and Wey and the Godalming navigation, and on their
return journey, the barges took the finished gunpowder to temporary storage in
magazines at Barking Creek on the Thames Estuary. Charcoal was made at or near
the works from wood supplied from managed coppices nearby.
Historical sources indicate that at this time the gunpowder works had expanded
beyond the monument into areas to the west of Blacksmith Lane, known as the
workshop area, where the raw materials were stored and prepared, and to the
east of Albury Mill, known as the upper works, which is thought to have housed
water-driven stamp mills. These further areas have been significantly
disturbed by subsequent, unrelated redevelopment and are therefore not
included in the scheduling.
After Wharton's eventual bankruptcy, Chilworth works went into a period of
decline which lasted throughout the 18th and early 19th centuries. A
cartographic survey of 1728 shows that only the western part of the middle
works was operating at this time. Most early factory buildings and structures
situated within the monument were demolished during the late 19th and early
20th century phases of the works, although the mill races and some water wheel
pits survive. Some of the large, circular, edge-running crushing stones which
are distributed over the monument may also date to this earlier period.
Further traces of buildings, structures and associated remains dating to the
17th-early 19th centuries are likely to survive within the monument in the
form of earthworks, buried foundations and associated, below-ground remains. A
new period of expansion began in the 1860s with the introduction of steam
power to the site. From around 1885, the Chilworth works manufactured a form
of gunpowder for use with the newly developed heavy guns. Known as brown or
prismatic powder, the new explosive was made from charcoal produced from straw
rather than wood. The Chilworth Gunpowder Company was formed as the subsidiary
of a German company, and the factory was again extended into the eastern part
of the middle works. A number of impressive buildings survive from this
period, including the restored, almost intact shell of a large, six-bayed,
steam-powered incorporating mill, some of the components of which were
supplied by the German company Burbach in 1884-85. Surviving safety features
include a roof-level lever system which ensured that an explosion in one
chamber triggered a drenching mechanism in all six bays. To aid the
transportation of the large quantity of coal needed to fire the steam boilers,
a narrow gauge, single track, manually operated tramway was laid during the
1880s, connecting the various factory buildings and linking the works to
Chilworth and Albury railway station around 300m to the south. Three bridges
carried the tramway over the watercourses, the best surviving of which is a
rare, almost intact, mainly iron swingbridge of 1888 which carried the wooden
wagons over the southern canal on the approach to the railway station. Most of
the wooden sleepers and mainly iron rails have been removed, and the course of
the tramway is represented by low linear earthworks, although some stretches
of track are believed to survive in situ in the eastern part of the monument.
Small punts were also used to transport materials and finished products around
the site along the watercourses, and parts of the canal edges were
consolidated during this later period with earthen embankments reinforced with
corrugated iron.
Chemical explosives replaced gunpowder for most military purposes at the turn
of the 19th century, and from the early 1890s the manufacture of cordite, a
mixture of guncotton and nitroglycerine, was introduced at Chilworth. The
middle works were again updated and new factory buildings constructed at the
eastern end of the monument. Surviving buildings associated with the 1890-1915
cordite factory include a number of magazines, a packing house, a blending
house, a long, tall brick building which housed kneading equipment and
hydraulic presses, and a number of drying stoves. Many of the buildings are
protected by distinctive semi-circular traverses, or blast banks, constructed
of earth and corrugated iron. These were known in the wider explosives
industry as Chilworth mounds. The Chilworth works were taken over by the
Admiralty during World War I, and a further area, forming the southern part of
the eastern end of the monument, was developed for cordite production in 1915.
Most of the Admiralty structures were demolished at the end of World War I,
and the Chilworth works closed in 1920. The factory lands were auctioned in
1922, and the sale particulars include an annotated plan which details
structures surviving at the time. Many structures have since been wholly or
partly demolished, although some of these will survive in the form of ruins or
buried foundations.
An area near the eastern end of the monument was heavily disturbed by the
excavation of a large pond in 1983 and is therefore totally excluded from the
scheduling.
A number of features are excluded from the scheduling, these are all modern
fences, gates, seats, railings and footbridges, the modern surfaces of all
paths and tracks, and the two information boards situated in the western part
of the monument; the ground beneath and around all these features is, however,
included.

MAP EXTRACT
The site of the monument is shown on the attached map extract.

Source: Historic England

Reasons for Scheduling

Gunpowder was the only explosive available for military use and for blasting
in mines and quarries until the mid-19th century. Water-powered manufacturing
mills were established in England from the mid-16th century, although powder
had been prepared by hand for at least 200 years. The industry expanded until
the late 19th century when high explosives began to replace gunpowder. Its
manufacture declined dramatically after the First World War with British
production ceasing in 1976. The technology of gunpowder manufacture became
increasingly complex through time with the gradual mechanisation of what were
essentially hand-worked operations. Waterwheels were introduced in the 16th
century, and steam engines and water turbines from the 19th century. Pressing
and corning were also introduced between the 16th and 19th centuries to
improve the powders. Pressing improved the explosive power of the mill cake
and corning broke the pressing cake into different sizes and graded it with
respect to its fineness. Additional techniques were developed throughout the
17th, 18th and 19th centuries to improve the quality and consistency of the
finished product, and this in turn resulted in a variety of types of powders;
ranging from large coarse-grained blasting powders used in mines and quarries,
to fine varieties used, for example, in sporting guns.
Gunpowder manufacturing sites are a comparatively rare class of monument with
around 60 examples known nationally. Demand for gunpowder centred on the
London area (for military supply), other ports (for trade), and the main metal
mining areas. Most gunpowder production was, therefore, in Cumbria, the south
west, and the south east around the Thames estuary. The first water-powered
mills were established in south east England from the mid-16th century
onwards, and many of the major technological improvements were pioneered in
those mills. All sites of gunpowder production which retain significant
archaeological remains and technological information and survive well will
normally be identified as nationally important.

The Chilworth gunpowder works survive comparatively well over most of their
original extent and contain a number of impressive standing buildings in which
internal features, such as the fixings for machinery, remain in place. Most
phases in the well documented, 300 years of the factory's use are represented
by visible remains, with structures from the 1880s-90s surviving particularly
well. Important survivals include components of the original transport and
power systems which connected the site, and the 1880s tramway has been
identified as running on one of the earliest metric-gauge tracks in Britain.
The earliest phase of use during the 17th century is of particular
significance, with the Chilworth mills for a time operating as the only
authorised gunpowder producer in Britain. The later adaptation of the site
for the manufacture of brown powder and cordite provides important evidence
for developments in the explosives industry during the late 19th and early
20th centuries.

Source: Historic England

Sources

Books and journals
Crocker, G, A Guide to the Chilworth Gunpowder Mills, (1994)
Crocker, A, 'Surrey Archaeological Collections' in The Tramway at the Chilworth Gunpowder Works, , Vol. 82, (1994), 181-195
Warner, D, 'Surrey History' in The Great Explosion and the Later History of the Chilworth G Mills, , Vol. 1, 4, (1976), 131-157

Source: Historic England