'A' Magazine, Museum Buildings

A Magazine is a highly significant ammunition magazine dating from 1770-6, designed by Major Archer, Commanding Royal Engineer to Portsmouth District, with assistance from Captain Brewse and General Skinner. The building is constructed of brick in English bond with a slate roof.

The magazine takes the form of a broad gabled block heavily buttressed along its long sides, with a central raking buttress at each gable end. The building has a central entrance from the west side and an exit on the east side, connecting to the Rolling Way and other buildings in the complex. Internally, the magazine is arranged in two aisles connected by four broad cross-vaults, with a central throughway running the length of the building.

Approximately 20 metres to the south and north are high traverse walls, built for protection. The southern traverse wall is partly incorporated into B Magazine, while the northern wall forms the flank wall to the Quick Fire Shell Store.

The long west elevation features a central wide raking buttress containing a deep-set doorway with a cambered head. This is flanked by two further wide buttresses, all topped with stepped brick cappings beneath swept-down sections of the main roof and a similar stepped brick eaves cornice. Six very narrow ventilation slits, each 18 courses high and half a brick wide, are evenly spaced along the wall at approximately half-height. The east elevation is similar but has a lower structure attached centrally.

Each gable end has a large central raking buttress, tumbled in at the top beneath a ventilation slit. A hatch is set high on each end, with two smaller louvred openings. The southern end has louvred openings, while the northern end features round-arched windows. The roof is tightly clipped to the gable ends and fitted with a cast-iron gutter at the eaves courses.

Inside, the building provides a rectangular two-aisled space contained by very thick outer walls, approximately 2.1 metres thick. A central row of large square brick piers, each measuring 1.4 metres, carries two wide arched openings of approximately 1.8 metres and a smaller central opening. These openings are carried continuously to form two longitudinal barrel vaults, which are cut through by the cross vaults at the openings. All of this is executed in very fine English bond brickwork, with cut and formed bricks at the curved intersections. The vault thickness at the crown is just over one metre.

At the end of each aisle is a plain wall with blind recessed openings, but with a single window to each at the north end. The central piers have a hardwood rail set flush all around at arch springing level and at approximately one metre from floor level. The timber floor is laid in broad planks running longitudinally.

Originally, the magazine was completely enclosed by traverse protective walling, but the only free-standing section that remains is now to the south. This wall is two and a half bricks thick, built in English bond incorporating many blue headers. It stands approximately 3.2 metres high to the oversailing string in two courses, which carries a steeply pitched brick coping. On the magazine axis is a wide gateway fitted with two large framed plank doors with early ironwork, hung on square piers with flat cappings. At the left-hand end is a further square pier. To the right, the wall becomes part of B Magazine. The northern stretch of wall forms part of the Quick Fire Shell Store. The line of the original front wall is still marked by a continuous curbed run.

This is a particularly well-preserved and magnificent example of a late 18th-century classic British magazine type, with its characteristic pair of vaulted chambers and splendidly handled brick detailing. Although at first free-standing within its traverse walls, it later became linked with a series of related buildings, including a Rolling Way connecting directly with the waterside at the Camber. From around 1880, with the completion of E Magazine, it was used for storing small arms ammunition and filled rockets and shells.

Priddy's Hard's magazines and related structures date from the late 18th century. The site's expansion from the mid-19th century was closely related to the development of land and sea artillery and the navy's transition from the age of sail, powder and solid shot to the Dreadnought class of the early 1900s. Priddy's Hard retains the best-preserved range of structures that relate to this remarkable history of continual enlargement and adaptation, one that encompasses that of Britain's dominance as a sea power on a global scale.

The first phase of the site is bounded by the northern end of the Gosport Lines, defences for the protection of the naval dockyard that date back to the late 17th century and were extended around Priddy's Hard from 1757. The first plans were drafted in 1769, and the first phase of the complex was finished by the end of September 1777. This comprised a basin for powder vessels, a powder magazine, a cooperage for the repair of powder barrels, a rolling way for moving powder in barrows or trolleys, officers' houses and a shifting house for the examination of powder. Two additional magazines were projected and designed in 1776, and though never built, had a permanent effect on the shape of the site, as Captain Archer was ordered to strengthen the line of fortifications, which until 1779 comprised temporary palisades and fascines, to allow for them. The earthwork defences comprise a rampart with demi-bastions. The space so provided was to prove invaluable during the site's expansion in the next century.

Like the other magazines around Portsmouth, Chatham and Plymouth, the years of peace after the Napoleonic Wars had caused deterioration, particularly in the earthwork defences. This type of fortification needed a lot of attention. By 1809 they had been reported to be 'very ruinous', and in 1844 it was decided to restore and improve them, making the dry ditch a wet one and adding a drawbridge which protected the main entrance.

In 1847-8, a Laboratory complex was built at Priddy's Hard, following a decision to move it out of Portsmouth onto a more secure site. Apart from the operational buildings, this involved the construction of a small Expense Magazine to hold the explosives needed for the daily work in the Laboratory and the introduction of a transit system from the Magazine to the Expense Magazine. The principal function of the Laboratories through the Revolutionary and Napoleonic Wars had been the production of small arms ammunition, but this situation was to change, and with it the role of Priddy's Hard. The development of artillery meant a great increase in the use of filled shells and the fuzes required to detonate them, the preparation of fuzes being a natural extension of the work of the Laboratories. From 1845 shells were being introduced into naval service on an unprecedented scale, and in the Crimean War preparations were made for shell filling at Priddy's Hard. As the filling and emptying of the shells could not be carried out in a magazine and required dedicated facilities, the Laboratories came more and more to deal with the projectiles and propellants for sea and land-service artillery.

The development of new propellants and projectiles from the mid-19th century took place against the background of the arms race of the second half of the 19th century. Thus the construction of an armour-clad and steam-powered fleet, followed by the introduction of steel guns and rotating turrets, was accompanied by the development of ordnance which rendered the forts of the Palmerston government, initiated in 1859 in reaction to a perceived threat from the French, obsolete only 20 years after their construction. The smooth-bore 68-pounder had been the largest gun in service at the time of the Crimean War. Vast quantities of powder were needed as propellant and explosive filling for shells of the 110-ton monster guns of the 1880s, a decade which saw the development of more effective breech-loading systems and the emergence of the 12-inch gun as the standard naval armament.

The development of complex shell-filling systems at once differentiated Priddy's Hard from the other Depots, and the survival of such a complete complex is unique in a national context. The covered rolling way and buildings around the Camber, all originally wooden, were rebuilt in brick in the 1860s. An increasing number of buildings sited around the Camber were required to house the store of empty cases in which shells were individually packed and supplied to the ships. There are seven of these stores, ranging from 1859 to the 1890s. The vital job of repairing these boxes was carried out in the carpenters' shop.

The further redevelopment of Priddy's Hard began in 1860 with the construction of C Magazine. This was originally intended for the receipt of ammunition from ships and formed the terminus of a transport system linked to the Laboratory that was to play a key role in the development in the 1860s of a shell-filling complex. This eventually necessitated the demolition of the east ranges of the Laboratory, converted for shell-filling purposes in the 1860s but without the capacity to meet the demand as shells replaced solid shot as the standard naval ordnance. Tramways connected the Powder Pier and new E Magazine, built in 1878-9 as a replacement for A Magazine, to the Shell Filling Room and finally Shell Store of 1879 and Pier.

After an explosion at the Shell Filling Room in 1883 it was decided to move this activity to outside the historic fortified boundaries of Priddy's Hard and to distribute the activity among several small buildings. In 1886-7, therefore, a set of Shell Filling Rooms and a Fuzing Room, later joined by a Shell Filling Room for quick-firing shells, an Expense Magazine and Unheading Room, were built without the ramparts along the edge of Forton Creek. All the filling rooms were heated by hot water pipe supplied from a boiler house. Priddy's Hard was to develop the most complex internal communications system of any of the Yards until the rails for the powder line (1 foot 6 inch gauge) and the shell tramway (2 feet 6 inch gauge) were replaced by small self-propelled vehicles. The site had 240 employees in 1895, and larger Shifting Rooms were required to accommodate the expanded workforce.

Drastic changes in the administration of the Yards were made following the decision in 1890 to divide their control between the two Services. Spurred on by the arms race with Germany, the Admiralty at once began a great expansion programme which affected Priddy's Hard, Bull Point, and Upnor. A great change in the construction of magazine buildings was also caused by the introduction in the 1890s of the new explosives cordite and guncotton, which were stored under different conditions from gunpowder to the north and northwest of the ramparts. This part of the site has lost its former layout and most of its buildings, Bull Point at Plymouth now having the best-retained buildings representative of the new technology. 1896 saw the construction of a new Laboratory for filling cartridges, mainly with cordite, comprising frangible wooden buildings protected by massive traverses within the southern section of the 18th-century defences. Although temporary buildings whose plan forms are not clearly related to their intended and differing functions, their imprint on the landscape is marked by the dividing traverse walls. The preparation of shell cases by lacquering to prevent spontaneous chemical reactions and the development of the fuze from a rudimentary device to a complex piece of mechanism added other types of building. Massive shell stores were added to store the finished articles, together with a Mine Store, though at that period the Naval use of mines was very limited.

The development of Priddy's Hard after 1900 was affected by the traumatic event of an explosion in the New Shell Store in November 1902. It was decided that the site was far too close to the naval dockyard for bulk storage of explosives, and that the magazines should be used only as ready use magazines to supply the shell and cartridge filling rooms. A new magazine establishment, to be laid out on the same lines as Lodge Hill opposite Chatham dockyard, was proposed and after some false moves work began in 1908 at Bedenham. Priddy's Hard was now largely turned over to shell and cartridge filling.

The First World War brought about a great expansion of Priddy's Hard. This was partly because of the extension of the Laboratory to meet the increased need for filled cartridges and partly because of the introduction of new explosives and weapons systems. TNT, known in the Services as Trotyl, could be melted on a water bath and poured into shells, and a set of Trotyl Rooms were added in 1915. Amatol was an explosive consisting of a mixture of ammonium nitrate with trotyl, and stores were required for this. A new Mine Store was built in close proximity to the Amatol Store, while buildings dedicated to fuze filling were required. New weapons requiring storage, filling and maintenance were depth charges, bombs for aerial use, and the anti-submarine device of the towed explosive paravane.