"Grégoire de Saint-Vincent, the most gifted pupil of Clavius... received a sound grounding in Greek mathematics and was... acquainted with the works of Stevin and Valerio. The integration methods which he devised, probably... 1622-9, constituted an extension of Archimedes and [was] in no sense a development of the indivisible techniques of Galileo and Cavalieri. Unfortunately... the original manuscript was lost for many years and not [published] until 1647. Even so, the Opus geometricum attracted attention... it contained... [an] attempt to square the circle, but also... the systematic approach to volumetric integration developed under the name ductus plani in planum. ...geometric series played a significant part [in the integration method] and we are indebted to Grégoire for the clearest early account of the summation of geometric series. ...He goes on to consider... the paradox of Achilles and the tortoise, Zeno, he notes... had failed to recognize that the time intervals were in falling geometric progression, and... although the number of such intervals is infinite, their sum is finite."