Martin’s “Artificial Transit”

Benjamin Martin published several books on the transits of 1761 and 1769. His final transit text was Institutions of Astronomical Calculations (1773), which used the results of both transits to compute the dimensions of the solar system.
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In this book, Martin also took the opportunity to publicise the “artificial transit” which we have reconstructed. The mechanism photographed here is identical to the one working in the reconstruction; it is fitted to the reverse of the Sun disk and its gearing makes Venus move in proportion to the Sun’s motion. (Martin’s original engraving of the mechanism is also reproduced here.)
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