"The south arm of this estuary (Middle Harbour) runs westward for some distance, making of Middle Head a broad, bold peninsula. On the point of this, looking straight out to sea, stands the greatest fortification of Sydney & Port Jackson. The gun-carriages are placed in shallow, circular wells; the rock is caverned with magazines, and the powerful guns sweep all the water's face in front. To this point come the artillery, professional and volunteer, to practice marksmanship, and to learn with accuracy the distance of any point that could be occupied by an invading foe. Often on a Saturday afternoon the headlands are alive with spectators watching the practice. Here, too, the scientific maneuvres of the Easter Encampment (voluntary infantry) are elaborately gone through, while a detachment of infantry occupies an entrenched camp on the summit, and rehearses the operations necessary to prevent a landing on either of the Middle Harbour bays, and an attempt to take the forts in the rear. At the foot of the cliff at St. George's Head are embrasures reached by tunnels, in which are guns that command the line of the bar intended to protect any boom which might be constructed, or sweep the area of the torpedo field."
Sydney Heads form the entrance to Sydney Harbour (Port Jackson) in New South Wales Australia.North Head and South Head are to the north and south respectively and Middle Head and St George's Head are to the west and within the bay.The fortifications at Middle Head were constructed between 1801 and 1942 as part of Sydney Harbour's defence.The majority of the fortifications at Middle Head were built between 1870 and 1911 when the defence was moved from Sydney Cove to The Heads.Three sets of fortifications were built in Mosman and Middle Head in the 1870s.The battery on Middle Head was designed by the colonial architect James Barnett and constructed in1871.The whole area is linked by a network of tunnels that still existMost of the Middle Head area became a national park in 1979.The army moved out completely from George's Heights in 1997.