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Image credit: Portrait of Gother Kerr Mann, Mitchell Library, State Library of NSW (ML PXB 555)

Gother Kerr Mann: Colonial engineer

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10 min read
One of the nation’s foremost engineers during the 19th century, Gother Kerr Mann played an instrumental role in the development of Cockatoo Island’s penal establishment. Today, the remnant convict structures, including Fitzroy Dock, are a testament to his enduring impact.

This article, jointly written by volunteers Michelle Harper and Fay Jubb, shows the civic-minded engineer was a man who wore many hats well.

Soldier, engineer, councillor, husband

Mann was born at Queenstown, Ireland on 20 February 1809, the sixth child of Major General Cornelius Mann of the Corps of Royal Engineers and his wife Sarah Mann (née Fyers). Following in his father’s footsteps, Mann enrolled in the East India Company Military Seminary in Addiscombe, Surrey in the 1820s. Colloquially known as Addiscombe College, the seminary trained young officers to serve in the East India Company’s private army in India. Here, Mann trained as both a colonial engineer and soldier.

In 1828, Mann joined the Royal Bombay Horse Artillery, bearing a commission signed by King George IV, and was posted to India, where he rose to the rank of Captain. Due to poor health, he left departed India in 1836 and travelled to Sydney aboard the East India Company’s frigate Tigris. The following year, he embarked on a trip to New Zealand aboard the HMS Rattlesnake.

By 1838, Mann had returned to Sydney where he married Mary Joanna Hely – the 19-year-old daughter of the late Frederick Hely, the colony’s former Superintendent of Convicts. In addition, he established a private engineering practice and, from 1839, served as local magistrate in the district of Gosford. He would go on to become an elected district councillor for Gosford a decade later.

During the depression of the early 1840s, Mann was listed as insolvent by the NSW Government Gazette after numerous failed business ventures. He subsequently found employment with the colonial government. Working as a draughtsman in the Department of Royal Engineers, he designed a lightweight mortar which was used in the New Zealand Wars, which was commonly known as the Māori Wars at the time.

Fitzroy Dock and the rise to superintendent

On 3 February 1847, Mann was appointed Engineer in Chief of Cockatoo Island and became responsible for designing all civil and corrective buildings at the penal establishment. His first major task was designing a dry dock and overseeing its construction with convict labour.

On 6 September 1848, Mann ordered the ignition of 500 pounds of gunpowder to demolish the sandstone cliff on the island’s south-east corner and progress the dock’s construction. A crowd gathered on Balmain Peninsula to watch the spectacle while boats were warned off and the island’s prisoners ordered to take shelter. The ensuing explosion caused the cliff to tumble into the sea. This marked the first occurrence of electrical firing of gunpowder in the colony.

On 5 June 1854, the first stone of sill for the dock was laid during a ceremony by Charles Fitzroy, the Governor of NSW. Further, it was renamed Fitzroy Dock in honour of its namesake. A man of many interests, Mann established a battery of artillery that same year and was appointed commandant of the colony’s Volunteer Artillery Corps. In July 1855, he was also appointed Commissioner of Railways for New South Wales – this followed the government’s takeover of the bankrupt Sydney Railway Company.

The completion of Fitzroy Dock in 1857, following ten years of construction, signalled the beginning of Cockatoo island's storied maritime era (1857 to 1991). On 30 September 1857, the dock received its first vessel: the punt of a steam-powered dredging boat known as “Hercules”. Two months later, on 1 December, HMS Herald became the first sailing vessel to use the dock. Although the dock had been officially completed, works would continue for some time. Today, Fitzroy Dock holds the distinction of being both the earliest graving dock commenced in Australia and the only surviving example, nationally, of a dry dock constructed by convicts.

In 1859, Mann became the Superintendent of Cockatoo Island’s penal establishment, succeeding Charles Ormsby. As he still held the title of Engineer in Chief, he found himself responsible for every aspect of island life, both civil and penal. Mann continued to run Cockatoo Island until his retirement in 1870, a year on from the penal establishment’s closure.

Mann’s family, home and enduring legacy

When Mann was first appointed Cockatoo Island’s Engineer in Chief, he lived at St Leonards and commuted to his office in Circular Quay and to the island by ferry. In 1853, he purchased a two-storey Georgian mansion, which he later named Greenwich House, from George Green for £1250. He lived there with his family until his promotion to Superintendent necessitated that he reside on the island. Initially, his wife and 12 children – five boys and seven girls including Minnie – remained at Greenwich, a short boat ride away. From 1864 until Mann’s retirement, his family lived with him at Biloela House on the upper island.

Mann died on New Year’s Day 1899 – just a month and a half shy of his 90th birthday – and was buried at St Thomas Rest Park in Crows Nest. His wife, Mary, passed away two years later. A year prior to his death, Mann and his wife celebrated their diamond wedding anniversary at Greenwich House, surrounded by their 12 children, 19 grandchildren and 4 great-grandchildren. Greenwich house remained in the family’s possession until 1949.

Mann’s designs for Cockatoo Island, including the Free Overseers' Quarters and his extension to the Prisoner Barracks, survive to this day. His sketchbooks, which contain rough pencil sketches of the island and its structures, are held in the Mitchell Library.

In Greenwich, Manns Point, Manns Park, Gother Avenue and Manns Avenue are named after him. Mann Street in Gosford also bears his name and plaque on the front wall of the Old Courthouse commemorates him. It reads: “He looked ahead with confidence”.


Article was originally published on 16 April 2021.


"[Mann] looked ahead with confidence"

– Plaque, Old Courthouse on Mann Street in Gosford

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