Platypus Submarine Gold Dredge - A Brief History

May 11, 2010
Mike Bown

Remains of the Platypus Submarine Gold Dredge - Mike Bown

The story behind the curious remains of New Zealand's first submarine, built in 1874, lying beside the Strath Taieri Museum at Middlemarch, Central Otago

In the 1860s New Zealand was gripped by ‘gold fever’ after the discovery of easily won alluvial gold in Otago and West Coast rivers. Early miners panned gold from the easily accessible gravels near the riverbanks and in old riverbeds. The easy gold was soon exhausted and attention turned to dredging deeper rivers, particularly the Clutha (then known as the Molyneaux) and its tributaries the Kawarau and Shotover rivers.

Gold Dredging

Miners dredged the submerged gravels along the edges of deeper rivers with spoon dredges consisting of a leather bag tied around an iron hoop attached to a stout pole (rather like a robust butterfly net). Although miners could now reach and process deeper gravels the spoon dredges were unwieldy and inefficient and still could not reach the potentially rich deposits in the deepest river channels.

Proposal for a Submarine Dredge

In August 1872, Mr R.W. Nuttall arrived in Dunedin from Melbourne, Australia with plans for a ‘sub-marine boat apparatus’ designed for digging and sluicing under water. Nuttall claimed a prototype had been built and successfully tested in the Yarra River.

The plans illustrated a submarine shaped, self-contained diving bell equipped with compressed air and ballast chambers to control buoyancy in the same manner as a modern submarine. A working chamber accommodated the crew and gravel washing machinery. After descending to the riverbed, an eight square-feet hatch in the floor of the working chamber would be opened to allow the miners to dig up and process the riverbed gravel to recover the gold. The ‘crew’ of three miners was expected to work 6-hour shifts for 2 shillings per hour per man. There was no mechanism for communication between the submerged dredge and the supporting crew above.

Financial Woes

Nuttall issued a prospectus for the New Zealand Rivers Gold Mining Company seeking capital of £10,000 to build up to 40 such vessels to work the gold-rich Otago rivers. Despite a generous projected dividend of 500% per annum Nuttall’s company failed to raise even the first £1500 needed to build a prototype. Nuttall’s company was taken over by the New Zealand Submarine Gold Mining Company Ltd which contracted the Dunedin Ironworks (R.S. Sparrow & Co.) and the Railway Foundry to construct a prototype.

"I Name This Boat the Platypus"

In August 1873 the directors took possession of the vessel. Fitting out took another three months and on 14th December the boat was launched successfully from the Rattray Street wharf. Miss Grant, a friend of one of the directors, formally christened the boat Platypus with the traditional bottle of champagne.

The completed Platypus looked very much like a modern submarine. The vessel was 35ft (10.6m) long, 7ft 2in (2.2m) in diameter with a pointed nose and constructed from riveted iron plate. A dome amidships provided access to the interior and paddle wheels either side of the dome, driven by the river current, would power the internal air pumps.

Trials in Otago Harbour

On January 30th 1874, the Platypus was towed out into the Otago Harbour accompanied by a steamer carrying curious public observers. Eight men boarded the platypus including the designer (Monsieur Villaine) and his son, a company director and four men hired to work the pumps.

After screwing down the dome hatch, it took nearly two hours for the Platypus to reach the harbour bed, even though the vessel was only just submerged. After another 2 hours without any sign of activity the Platypus began to resurface but a strong wind jammed it under the stern of the support boat.

The Platypus was towed to shallow water and the men, exhausted from pumping, finally emerged after a total of 4 hours and 20 minutes. Leaking air-pump valves had made it difficult to create sufficient pressure to expel water ballast and refloat the Platypus. It also prevented them from opening the bottom hatch to get access to the harbour bed. Further modifications would be required before trials could continue.

The Demise of the Platypus

Three months later the New Zealand Submarine Gold Mining Company Ltd went into liquidation and the Platypus and patent rights were sold at auction for £400. The vessel was stripped of equipment and the empty hull lay forgotten and rusting by the Rattray Street wharf for 50 years. In 1924 it was bought for £10, cut into three sections (a fourth middle section housing the dome and paddles has disappeared) and transported to Barewood Reefs, ironically the site of a former gold mining settlement. For many years the largest section was used as a household water tank on Pukerangi Farm Station.

Final Resting Place of the Platypus

In 1991 the historical significance of the remains of the Platypus was recognised and the remains were donated by W.F. Stewart, owner of Pukerangi Station, to the Strath Taieri Museum in Middlemarch.

Lying beside the museum building, New Zealand’s first submarine now attracts the curiosity of visitors to Middlemarch and cyclists on the Central Otago Rail Trail.