Abstract

In two recent articles by Russell and Whiteside, the reception of those particular conclusions of Kepler that have come to be called his laws of planetary motion has been subjected to the first research beyond the pioneering efforts of Delambre at the beginning of the nineteenth century. Independently conceived, and directed towards quite different ends, these two investigations overlapped in only one substantial area—their survey of citations of Kepler's second law by English astronomers between 1650 and 1670. Not surprisingly, they reached essentially identical conclusions about the situation in 1670. Finding ‘equant’ theories instead of the law of areas, wherever he looked, Russell qualified his general claim ‘that the importance of Kepler's ideas during the period [up to 1666] has been greatly underestimated’, to the extent of describing the history of the second law as ‘chequered’ and ‘complicated’. And Whiteside simply reported that Kepler's scheme for reckoning motion in the elliptical orbit ‘was seemingly firmly accepted by no one, and even its formal enunciation but rarely stated in the period’