Philosophical Transactions of the Royal Society Part 43

_Correct in Number._ 19.

Page, 342. line, 33. read _mixt Ores_, in stead of, _mixt with Ores_.

_London_, Printed for _John Martin_, Printer to the _Royal Society_, and are to be sold at the _Bell_ a little without _Temple-Bar_.

{369}

_Numb._ 21.

PHILOSOPHICAL _TRANSACTIONS._

_Munday_, _January_ 21. 1666.

The Contents.

_An Account, formerly promised, of Monsieur _Hevelius's_ Calculation of the late _Solar Eclipse's_ Quant.i.ty, Duration, &c. The Figure of the Star in the Constellation of _Cygnus_, together with the New Star in it, discovered some years ago, and very lately seen again by the same Mr. _Hevelius_. An Extract of a Letter, written by Mr. _Auzout_, concerning a way of his, for taking the _Diameters_ of the Planets, and for knowing the _Parallax_ of the _Moon_: Giving also a Reason, why in the _Solar Eclipse_ above-mentioned, the _Diameter_ of the _Moon_ did increase about the end. A Relation of the loss of the Way to prepare the _Bononian Stone_ for shining. A Description of a _Swedish Stone_, affording _Sulphur, Vitriol, Allum_, and _Minium_. A Relation of the Raining of Ashes. An Extract of a Letter from _Rome_, rectifying the Relation of _Salamanders_ living in Fire. An Account of several Engagements for _Observing of Tydes_. Some Suggestions for Remedies against Cold. A Relation of an uncommon accident in two Aged Persons.

An Account of Two Books, _I. ISMAELIS BULLIALDI ad Astronomos Monita duo: Primum, de Stella Nova, in _Collo Ceti_ ante aliquot annos visa.

Alterum, de Nebulosa Stella in _Andromedae_ Cinguli parte _Borea_, ante biennium iterum orta. II. ENTRETIENS sur les vies & sur les Ouvrages des plus excellens Peintres, antients & modernes, par M. FELIBIEN_._

_Monsieur _Hevelius_'s Calculation of the late _Solar Eclipse's_ Quant.i.ty, Duration, &c._

This _Calculus_ was not long since communicated by Monsieur _Hevelius_ in a Letter to the _Publisher_, as follows, {370}

_Eclipsis Solaris._

_Observata An. 1666. D. 2. Julii, St. N. Mane, a Johanne Hevelio._

----+-----------------+-----------+----------+--------+--------+---- Ordo| |Temp aestin | |Alt.i.tude| | Pha-|Quant.i.tas |sec. horol |Temp. sec.| [Sun] |Tempus | sium|Phasium |ambulat. |Sciother. | |correct.|Anim.

----+-----------------+-----------+----------+--------+--------+---- | |H. ' " |H. ' " | . ' |H. ' " | | |5.51.11 |5.51. 0 |17.45 |5.53.12 | 1.

| |5.57. 5 |5.57. 0 |18.37 |5.59.28 | | |6. 0. 0 |6. 0. 0 |18.55 |6. 1.28 | ----+-----------------+-----------+----------+--------+--------+---- |Initium |6.55.30 | | |6.57.30 | 2.

1 |0-3/8 dig. |6.57.30 | | |5.59.30 | 2 |0-3/4 |7. 0.23 |7. 0. 0 | |7. 2.23 | 3 |1-1/8 |7. 2.30 |7. 2. 0 | |7. 4.30 | ----+-----------------+-----------+----------+--------+--------+---- 4 |1-1/2 dig. |7. 4.50 |7. 5 fere.| |7. 6.50 | 5 |1-3/8 fere. |7.10.57 |7.10 | |7.12.57 | 6 |3-3/8 |7.14.59 |7.15 | |7.16.59 | 7 |3-3/4 |7.17.50 |7.18 fere.| |7.19.50 | ----+-----------------+-----------+----------+--------+--------+---- 8 |4-3/8 dig. |7.21.35 |7.21 | |7.23.35 | 9 |4-2/3 |7.23.43 |7.23 fere.| |7.25.43 | 10 |5-1/4 |7.27.53 |7.28 | |7.29.53 | 3.

11 |6 |7.31.50 |7.32 | |7.33.50 | ----+-----------------+-----------+----------+--------+--------+---- 12 |6-3/4 |7.36.55 |7.37 | |7.38.55 | 13 |6-7/8 paul. plus.|7.38. 5 |7.38 | |7.40. 0 | 14 |7-1/8 |7.39.45 |7.39 | |7.41.45 | 15 |7-1/4 paul. plus.|7.42.30 |7.42 | |7.44.30 | ----+-----------------+-----------+----------+--------+--------+---- 16 |7-1/2 |7.44. 6 |7.44 | |7.46. 6 | 17 |7-2/3 |7.46. 0 |7.46 | |7.48. 0 | 18 |8 fere |7.48.25 |7.48 fere | |7.50.25 | 19 |8-1/5 |7.51.15 |7.51 | |7.53.15 | ----+-----------------+-----------+----------+--------+--------+---- 20 |8-1/4 paul. plus.|7.53.37 |7.52 | |7.55.37 | 21 |8-3/4 |7.55.45 |7.56 fere | |7.57.45 | 22 |8-3/4 paul. min. |7.59. 5 |7.59 | |8. 1. 5 | 4.

23 |8-1/5 |8. 6.30 |8. 6 | |8. 8.30 | {371} ----+-----------------+-----------+----------+--------+--------+---- 24 |7-3/4 |8.11.25 |8.12 | |8.13.25 | 5.

25 |7-1/4 fere. |8.17.30 |8.18 | |8.19.30 | 26 |7 fere. |8.19.41 |8.19 | |8.21.41 | 27 |5-7/8 |8.28. 8 |8.28 | |8.30. 8 | ----+-----------------+-----------+----------+--------+--------+---- 28 |5-1/2 fere. |8.30.14 |8.30 | |8.32.14 | 29 |4-3/4 |8.36.25 |8.36 | |8.38.25 | 30 |3-5/8 |8.43.19 |8.43 | |8.45.19 | 31 |3-1/4 |8.46.12 |8.46 fere.| |8.48.12 | ----+-----------------+-----------+----------+--------+--------+---- 32 |3 |8.47.32 |8.47 | |8.29.32 | 33 |2-3/4 |8.50.57 |8.50 | |8.52.57 | 34 |2-1/2 fere |8.54.15 |8.54 | |8.56.15 | 35 |1-3/4 |8.58.24 |8.58 | |9. 0.24 | ----+-----------------+-----------+----------+--------+--------+---- 36 |1-1/8 |8.59.35 |8.59 | |9. 1.35 | 37 |0-5/6 |9. 1.38 |9. 1 | |9. 3.38 | 38 |0-1/2 |9. 3.20 |9. 3 |Alt.i.t. |9. 5.20 | 39 |Finis. |9. 6.53 |9. 6 |[Sun] |9. 8.53 | 6.

----+-----------------+-----------+----------+--------+--------+---- | |9.23. 6 | |47.33 |9.25 28 | | |9.24.16 | |47.42 |9.26.45 | | |9.28.29 | |48.10 |9.30.42 | | |9.30.36 | |48.28 |9.33.12 |

_Animadvertenda._

1. Qud Sciateric.u.m c.u.m correcto tempore non omnino convenit, non-nisi Lineae Meridianae imputandum.

2. Initium circa 79 gr. a puncto _Zenith_ occasum versus contigit.

3. Hujusque Semidiameter Lunae aequalis ext.i.tit Solari.

4. Maxima obscuratio ext.i.tit digit. 8.25' hora 8.2'.

5. Hic Semidiameter _Lunae/_ ad 8" vel 9" major apparuit.*

* _See Numb. 19 of the Philosophical Transactions, p. 347._

6. Punctum finis dist.i.tit a verticali ad Ortum 143 gr.

This Observation is by the same _Astronomer_, represented also by the _Figures AAAAAA_; as that of the _Horizontal Eclipse_ of the _Moon_, is, by the _Figures BB_.

[Ill.u.s.tration]

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_The Figure of the Stars in the Constellation of _Cygnus_; together with the _New Star_ in it, discover'd some years since, and very lately seen by M. _Hevelius_ again._

The Relation concerning this _New Star_ in the _Brest of Cygnus_, very lately discover'd again at _Dantzick_, by M. _Hevelius_, was publish't _Numb_. 19. _p_. 349. The _Figure_ of that _Constellation_, with the _New Star_ in it, was thus, hastily drawn, sent over by that Observer.

[Ill.u.s.tration]

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_An Extract of a Letter written _Decemb. 28. 1666_. by M. _Auzout_ to the Publisher, concerning a way of his, for taking the _Diameters_ of the _Planets_, and for knowing the _Parallax_ of the _Moon_; as also the Reason, why in the _Solar Eclipse_ above calculated, the _Diameter_ of the _Moon_ did increase about the end._

I did apply my self the last Summer to the taking of the _Diameters_ of the Sun, Moon, and the other Planets, by a Method, which one M. _Picard_ and my self have, esteem'd by Us the best of all those, that have been practis'd hitherto; since we can take the _Diameters_ to _Second Minutes_, being able to divide one foot into 24000. or 30000. parts, scarce failing as much as in one only part, so as we can in a manner be _a.s.sur'd_, not to deceive our selves in 3. or 4. _seconds_. I shall not now tell you my Observations, but I may very well a.s.sure you, that the _Diameter_ of the _Sun_ has not been much less in his _Apogee_, than 31. m. 37. or 40. sec. and certainly not lesse than 31. m. 35. sec. and that at present in his _Perigee_ it pa.s.ses not 32. m. 45. sec. and may be lesse by a second or two. That, which is at the present troublesome, is, that the _Vertical_ Diameter, which is the most easie to take, is diminisht, even at _Noon_, by 8. or 9. sec., because of the _Refractions_, which are much greater in Winter than Summer at the same height; and that the _Horizontal_ Diameter is difficult, because of the swift motion of the Heavens.

As for the _Moon_, I never yet found her Diameter less than 29. m. 44. or 45. sec. and I have not seen it pa.s.s 33. m. or if it hath, it was only by a few _seconds_. But I have not yet taken her in all the kinds of situations of the _Apogees_ and _Perigees_ which happen, with the _Conjunctions_ and _Quadratures_. I do not mention all, what can be deduced from thence, but if you have Persons at _London_, that observe these _Diameters_, we may entertain our selves more about this Subject, another time. I shall only tell you, that I have found a Way to know the _Parallax_ of the _Moon_, by the means of her _Diameter_: _Vid_. If on a day, when she is to be in her _Apogee_ or _Perigee_, and in the most _Boreal_ Signes, you take her Diameter towards the _Horizon_, and then towards the _South_, with her _Alt.i.tudes_ {374} above the Horizon. For, if the Observation of the Diameters be exact; as in these Situations the Moon changes not considerably her Distance from the Earth in 6. or 7. hours, the _Difference_ of the Diameters will shew the Proportion there is of her Distance, with the Semi-diameter of the Earth. I do not enlarge, because that as soon as one hath this _Idea_, the rest is easie. The same would yet be practis'd better in the places, where the Moon pa.s.ses through the _Zenith_, than here, for the greater the difference is of the Heights, the greater is that of the Diameters. I do not note (for it easily appears) that, if one were under the same _Meridian_, or the same _Azimuth_ in two very different places, and took at the same time the Diameter of the Moon, one would do the same thing, though this Method goes not to preciseness.

From what has been said, may be collected the reason of the Observation, which M. _Hevelius_ made in the last _Eclipse of the Sun_, touching the increase of the Moon's Diameter about the end. I am exceeding glad, that a person, who probably knew not the cause of it, has made the Experiment: but it is strange, that until now no Astronomer has foreseen, that that should happen, nor given any precepts for the Change of the _Moons Diameter_ in the _Eclipses of the Sun_, according to the places, where they should happen, and according to the Hour and Height, the Moon should have. For, what hapned in that _Eclipse_ of Augmentation, would have faln out contrarily, if it had been in the Evening; for, the Moon, which in that _Eclipse_, that began in the Morning, was higher about the end than at the beginning, was nearer us, and consequently was to appear bigger: But if the _Eclipse_ should happen in the Evening, she would be lower at the end, and therefore more distant from us, and consequently appear lesser. So also in two different places, whereof one should have the Eclipse in the Morning, and the other at Noon, the Moon should appear bigger to him that hath it at Noon: And she must likewise appear bigger to those, who shall have a leser _Elevation_ of the _Pole_ under the same _Meridian_, because the Moon will be nearer them.