Another Letter from the Same Hand, upon the Same Subject with the Former

Another Letter from the same hand, upon the same Subject with the former. Dom. Henrico Oldenburgio, Illustrissimae Regiae Societ. Secretario, amico honorando, Joh. Hevelius, S. Iteras meas, die 1 Maii super datas, spero Te optimè accepisse, atque ex eis intellectisse, Cometam hic Gedani die 27 April. primùm illuxisse: nunc ad continuandam hujus phænomeni Histò- violam nonnulla adhuc addam, quid videlicet tum ejus cursu conti- gerit, & quando plane hic visui se se subduerit. Atque ita die 1 Maii vesperi, ut in dictis literis vobis perscripseram, sperabam me Cometam quoque observaturum, ut ut in decliviore situ; sed adversa aëris temperies, id omnino tum impediebat: At vero die 2 Maii vesperi, Cælo rursus sereno, horâ 8.45', etiam si eà in parte Cæli, nulla adhuc Stella emicarent, intensumque crepusculum existere, nihilominus Cometam Tubo Optico ivimus quaestum, quem etiam protinus inveni, scienti omnes spectatores testabantur. Paulò post, illum in altitudine 3.30' sextante majori, à Capella & Lucida Ca- thedrae Cassiopeæ dimensum sum: Caudam referebat, ratione cre- pusculi, valde tenuem, quam inter utrumque genu Cassiopeæ, pro- pius tamen sinistro exporrigerat: occidebat eà vesperâ horâ 10 Cir- cium versus, h.e. Nord Nord west. Die 3 Maii mane, Cælo rursus perquam sereno Cometa oriebatur Boream versus, h.e. Nord Nord ost, horâ scilicet 1.23', quamquam Cauda paulò citius à nobis dete- éta, nempe hor. 1.18'; observatus est à Capella, Lucido Latere Persei, & Lucida Cathedrae Cassiopeæ, versabatur in 14 grad., cum Sole ferè in ipsâ Conjunctione, Latitudinem habens 17 grad., & tantam etiam distantiam ferè ab ipso Sole. Caudam hác die longè prolixiorem & acutiorum satisque splendidam 2 vel 3 ferè grad. ostendebat. Hincque à me aliisque spectatoribus visu pollutibus nudo oculo ad hor. 3.34' deprehensus est, & Telescopio ad hor. 3.40', in altitudine 11°.30'; adeò ut Sol eo tempore tantummodò 6 grad. infra horizontem lateret; imò diutius il- lum vidissimus, nisi nube culæ illum nobis eripuisset: Motus diur- nus decrescere videbatur, quantum conjecturà absque omni calculo assequi potui. Nam inter 29 & 30 April. 2°.45' ferè extitit; inter 30 Apr. & 1 Maii 2°.15'; inter 1 & 2 Maii 1°.55'; inter 2 & 3 Maii 1°.40'; sed ipsæ observationes calculusque id clariùs ostendent. Die 3 Maii vesperi Cælum minimè erat serenum; die vero 4 Maii vesperi, aëre admodum sudo, horâ 8.53', iterum Cometa detectus, sed obscurior paulò extitit, quàm diebus praecedentibus, tum Cauda brevior; dimensus eum sum à Capellà, & Lucidà Cathedræ Cassiopeæ. Die 5 Maii mane hor. 1.41'. Cometa primùm apparuit, ob obscuriores scilicet nubes horizontem insidentes; observatus rursús est, à Capellà, Cingulo Andromedæ, & Lucido Latere Persei, caudam dextrum genu Cassiop. versús exponens; versabatur in 17°, in 16° Latit. Bor., pariter in tantâ distantiâ à Sole; motus proprius à die 3 ad 5 Maii fuit ferè 2°.40', decrecente Latitudine, ab ipso initio scilicet ferè ad 3 grad.; sic ut in 29 April. motus proprius Cometa ad 5 Maii propemodum fuerit 12 grad. Fádem die vesperi clare quidem rursús illuxit, sed minime, ob gravissimas occupationes, observatus. Die 6 Maii mane, rursús illum dimensus sum; sed ruditer tantum, ob nubes, à Capellà inprimis & Lucidà Cathedræ Cass.; commemorabatur eo tempore in 18°, & Latit. Bor. 15°.30', Sole existente in 17°; motus diurnus erat 50°. circit. Quoad caput, quam caudam multò tenuior ac debilior videbatur, ob Solem non nisi 16° grad. à Cometà remotum. Die 6 Maii vesperi visus quidem Tubo Optico hor. sc. 8.35', cauda adhuc breviori & dilutori; sed cum in decliviòri siti, atque in crepusculo intenso existeret, nullo modo distinctè in nudos incurrebat oculis. Die 7 Maii deprehensus primum hor. 2.22' in altitudine 3°; observabatur rursús à Capellà, & Lucido Latere Persei, ut ut valde tenuis videbatur; occupabat eo tempore 19°, in Latitudine 15° Bor., & distantiâ à Sole 16° ferè, Sole existente in 18° grad.; motus ejus proprius magis magisque decrescet quantum colligere absque calculo dabatur. Die 8 Maii mane ab hor. 1. sedulo nudis quaestus est oculis, sed nusquam apparuit, Telescopio tamen 12 ped. inventus, caudam quidem adhuc praeferebant, sed brevissimam, paulò à circulo verticale sinistrum versus extensam. Quantum conjectura assequi potui; versabatur in 20°, in distantiâ à Sole 15°, qui tum 19 gradum possidebat; stabat ferè hoc tempore in linea recta, cum humero dextro Persei, & Algol. Medusa, exquisitè tamen à fixis observari bodie hand potuis. Diameter Cometae, ad Jovis diametrum comparata, vix ad dimidiæ partem accedebat. De reliquo, Tubi beneficio satis erat adhuc conspicuus, adeò ut eum ad hor. 3.45' distinctè conspicere potuerimus, in altitudine scilicet 9° ferè: unde colligere datur, arcum visionis vix 5° tum fuisse. Sol enim vix 5 grad. sub horizonte herebat; quo tempore omnes jam Stellaæ, excepto unico Jove, evanuerunt: Sol oriebatur limbo suo superiori hor. 4.6' ferè. Die 8 Maii vesperi Cometam nec nudis oculis, nec ullo Telescopio detegere amplius potuimus. Die 9 mane & vesperi, ut ut anxìè quaestus, nullà tamen ratione conspectus; nec die 10 Maii; sic ut certum I have this day received a Note from Sr. Jonas Moore, in which he informs me, that you have received Papers concerning the late Comet both from Mr. Hevelius and Mr. Cassini, and that you desire to know what I observed of it. I am glad to hear you have accounts of it from two such able persons, who having observed and made theories for the Comets which appeared near the same place twice of late at twelve years interval, viz in 1653, and 1665, may best inform us, what conformity there is betwixt the Motions of this and them, and whether it may probably be the same returned hither after two revolutions; or another: My Observations of it, by reason of our cloudy Nights, were so few, that I can determine nothing from them; however perhaps they may be of use to others, who had more frequent opportunities, and therefore such as they are, they are at your service. The first time that the Comet was taken notice of with us, that I can hear of, was about the middle of our Easter week; I believe it might have been observed long before, had not the unwonted cloudiness of our Heavens (which has permitted me to observe but 4 of almost 50 appulses of the Moon and Planets to fixed Stars foreseen hitherto) prevented. The first certain notice I had of it was on April 21. I waited the rising of the Comet; but immediately after midnight the Heavens were over-