Two lectures on comets : read in the chapel of Harvard-College, in Cambridge, New England, in April 1759. On occasion of the comet which appear'd in that month. : With an appendix, concerning the revolutions of that comet, and of some others. / - Winthrop, John, (Printed and sold by Green & Russell, at their printing-office in Queen-Street. Sold also by D. Henchman, at his shop in Cornhill,, 1759)