The correspondence in 1680 and 1681 between John Flamsteed and Isaac Newton on Flamsteed’s theory of the comet of 1680 tells half the story. Related manuscripts reveal Newton was pursuing his own comprehensive line of inquiry based on principles that were the antithesis of Flamsteed’s procedures. Following generally accepted views in England, Newton’s work was marked by critical evaluation of data but marred by uncritical use of simple calculating techniques based on what might be termed Platonic archetypes of straightness. Flamsteed’s (...) intervention provided useful data and allowed Newton to seek additional information. Although Newton supposedly briefly considered a solution that vaguely resembled his parabolic approximation of the path of the comet determined 5 years later, the evidence Newton provided (based on simple hypotheses) did not support such a highly curved path or one in which the sun apart from the solar vortex exerted influence. Newton’s work, including an alleged harmonic law of tails, was quietly abandoned in favor of other work. With new insight, Newton revived work on comets as fully gravitational objects immediately following Halley’s visit in 1684. This little known side of the episode provides a fresh opportunity to examine Newton’s sources and actual practice in developing a new line of inquiry. An appendix dating sections of Newton’s Waste Book entries on comets is included. (shrink)