Politicians and economists talk glibly about the so-called knowledge
revolution. The reality is that knowledge is fundamental to economic progress.
Consequently there have been many technological revolutions. The global impacts
of the invention of the steam engine and the development of the frozen meat
industry are well known. Another less publicised technological advance occurred
in Central Otago late in the nineteenth century. This was the adaptation of the
bucketladder dredge to the mining of placer deposits. A product of over 30 years
experimentation and innovation, New Zealand dredging technology was taken to the
Risdon Iron and Locomotive Works, San Francisco by R H Postlethwaite, a Dunedin
based mining engineer. New Zealand-style dredges built by Risdon operated
successfully in California, Alaska and the Yukon. Californian engineers
assimilated the best features of the New Zealand dredges with American (Bucyrus)
designs to produce a standard for the worldwide placer mining
industry.