This map shows the 28 meridional circuits established by John Turnbull Thomson in the late 1870s. Each circuit was a block of land with a primary station, whose location was carefully established by astronomical observations. The station formed the basis of the triangulation networks which followed.
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Alexander Turnbull Library
Reference: Appendices to the Journals of the House of Representatives, 1879, H-19 (B-K 969-H19/4-5)
Permission of the Alexander Turnbull Library, National Library of New Zealand, Te Puna Mātauranga o Aotearoa, must be obtained before any re-use of this image.