ABSTRACT
In his second Cutlerian lecture, Robert Hooke critically discussed the newly published Machina Cœlestis of Johannes Hevelius.1 When preparing this material for the press he took the opportunity of including illustrations of some astronomical instruments of his own devising.2 One of these was a quadrant mounted equatorially so as automatically to follow a chosen star as it moved across the celestial sphere. There is no evidence that Hooke ever made a practical version of this paper invention. Instruments mounted in this way and driven by a waterwheel were known in thirteenth-century China,3 but there is no reason to think reports of them had reached Europe, even though Tycho Brahe did make use of certain instruments rotatable manually on an equatorial frame.4
