Hariot was undoubtedly as great a mathematician and astronomer as Galileo. In 1607 at Ilfracombe and in South Wales, he had taken by hand and Jacob’s staff, the old patriarchal method, valuable observations of the comet of that year, and compared notes with his astronomical pupil William Lower, and afterwards with Kepler. This comet, now known as Halley’s, ought perhaps to have been named Hariot’s, for it confirmed his notions that the motions of the planets were not perfect circles and afforded probably the germ of his reasoning out the elliptical orbits of comets, especially afterhis friend and correspondent [see infra, pages 178-180] Kepler’s book _de Motibus Stella Atartis_ came out in 1609, and he had invented and improved his telescope or perspective ‘truncke’ or cylinder in 1609-10. It is not positively stated that Hariot held direct correspondence with Galileo in 1609 and 1610 or even later, but the evidence is strong that he was promptly kept informedof what was going on in Italy in astronomical and mathematical discovery, as well as in Germany and elsewhere. That he was using a ‘perspective truncke’ or telescope as early as the winter of 1609-10, and that his ‘servaunte’ Christopher Tooke (or as Lower in 1611 familiarly called him’ Kitt’) made lenses for him and fitted them into his ‘trunckcs’ for sale by himself, is known. From this circumstance,and from the fact that he disposed of many ‘trunckes’ by his will, and left a considerable stock of them to Tooke, it is manifest that he manufactured and traded in telescopes from 1609 to 1621. With his invention of the telescope then it required no correspondence with Galileo to induce him to rake the heavens and sweep our planetary system for new astronomical discoveries. To an astronomer of his activity and mathematical acumen these discoveries followed as a matter of course. Like Galileo he may have borrowed from the Dutch (or quite as likely they of him) the idea that by a combination of lenses it was possible to bring distant objects near, but that he worked out the idea independently of Galileo admits hardly of a doubt. But he seems to have been less ambitious than Galileo to claim priority in either the invention or the discoveries that immediately followed. In this connection the following hitherto unpublished letter will be read with interest: LETTER OF SIR WILLIAM LOWER _in South Wales to_ THOMAS HARIOT _at Sion_ 21 _June_ 1610. _Printed from the holograph original in the British Museum_