In 1661 Gerard Kinckhuysen published at Haerlem an introduction to algebra written in Dutch. Because of the clarity and compactness of its presentation it was considered suitable for dissemination to a wider class of readers than those able to read Low Dutch. Nicolaus Mercator, a wellknown mathematician of German origin, who had come to England as a young man in the later 1650s, was asked by Lord Brouncker to prepare a Latin translation of it. To this Isaac Newton, at the request of Isaac Barrow and John Collins, added explanatory notes and comments, and the manuscript was sent to Collins in London on 11 July 1670. Newton's draft, though still unpublished, is preserved, but Mercator's original translation was believed to have been lost. Only recently I rediscovered it in the Bodleian in a bound volume deriving from the estate of the Oxford mathematician John Wallis, which contains several books and pamphlets once in his possession.

This article is divided into four sections:

I. A survey of Kinckhuysen's Algebra ofte Stel-konst.

II. A summary of Newton's notes and additions to it.

III. An account of the unsuccessful efforts of Collins and Newton to publish the Mercator translation, enlarged with Newton's comments—this is abstracted from Collins' correspondence with Newton, Wallis and Gregory.

IV. A description of the volume now in the Bodleian Library, press-marked ‘Savile G. 20’, which has Mercator's translation interleaved with the printed Dutch original and bound with other books once owned by Wallis.