Johannes Hevelius

Author of the First Complete Moon Atlas

(April 1685)

The Telescope vs the Naked Eye

“ Given this convenient opportunity,  and having published my little work of observations,  namely Annus Climactericus, I did not want to neglect my duty any longer, but to offer it duly to you and the Royal Society... Humbly asking that you will receive,  in good spirit and in love of truth, these little pages ... written in defense of my observations, and that you, rnoreover, deem the author worthy of your protection against all envious persons and those wishing me ill. In the said little work you will not only see discussed that controversy between Hooke and me long ago conducted with mere words and [more recently] when Halley was here [whom the Royal Society sent to me at the end of 1679] clearly and with the eye [itself], but you will also find my observations of planets as well as occultations and eclipses, made by me here in Gdansk [Danzig] in my new observatory, after that abominable misfortune of mine.”   [The abominable misfortune was the fire which destroyed Hevelius' observatory and many of his books. The Annus Climactericus is his defense of naked-eye measurements of stellar positions].        

 

Hooke argued that while he could measure with a telescope an angle of 1 second of arc, the minimum angular separation given by a normal eye was, at the most, about an angle of 30 seconds to 1 minute of arc. Unless two stars were separate further than this amount, they would appear as one. Hevelius did not deny this. He claimed, however, that good eyesight and long practice had enabled him to exceed these limits. In proof, he sent a set of measures to Hooke, requesting him to check them with his own instruments.  These remarks, and others like them, received the strong and tactless censure of Hooke in his retaliatory work: Animadversions.  Hooke passed over Hevelius' optical difficulties but ridiculed his instruments and slighted the value of his observations.  This did but exasperate Hevelius, but made him adhere more obstinately to his former practice. Eventually, the dispute became so heated that the Royal Society intervened and, in 1679, sent young Edmund Halley to Danzig to ease the tension. Hevelius received him warmly,  and the two astronomers, one at the beginning and the other near the end of his career, made and compared observations. Halley found that Hevelius’ claims were justified but he could not convince his host of the greater accuracy of the telescopic sight.  Even after this, a further passage of arms ensued between Hevelius and Hooke in 1685, but to the gain of neither.

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Hevelius, Johannes.  2 ALS  To Francis Aston.  2 ½; 2 pp.  Folio.  In a cloth slipcase., Gdansk, April - 29 December 1685

Oldenburg, Henry. [Secretary: Royal Society] 2 autograph letters, signed.  To Johannes Hevelius.  London, 29 Aug- 25 Sept 1674

 

            An important collection of 4 autograph letters illustrating the relations between the astronomer Johannes Hevelius (1611-1687) and the Royal Society.  Two letters were written by the secretary of the Royal Society Henry Oldenburg to Hevelius in 1674; two others were written by Hevelius to Francis Aston, the new secretary, in 1685.  The letters do much to illuminate the traffic in books and scientific instruments which drew European scientists together in the later 17th century. 

1.  Oldenburg begins by writing that he has not received a reply to his letters of 23 March and 30 March 1674 (o.s.) [although Hevelius had indicated in his letter of 9 May, received by Oldenburg on 17 May (o.s.) that he had received the letter of 23 March, see:  Oldenburg, 10, 572].  Oldenburg therefore recapitulates these two letters [which are printed:  Oldenburg, 10, 531-533, 550-551].

About the number of copies of Machina coelestis received, Oldenburg would like to send the money from the sale of them by bill of exchange.  Would Hevelius please designate a merchant?

He has sent Robert Hooke’s Attempt to prove the motion of the earth from observation [1674] with his letter of 30 March.  Although this is in English, a certain Englishman named Kirkby, then in Gdansk (Danzig), would help Hevelius read it.

            He has also sent John Wallis’ new edition of Grammatica linguae anglicanae [1674] and Robert Boyle’s The excellency and grounds of the mechanical hypothese [1674].

            The recapitulation of his earlier letters:  “There is now in the press the said Hooke’s description and illustration of some astronomical quadrant which he thinks is better and more useful than all astronomical instruments devised and used up to now.  As soon as the little book will have come out, you will be in possession of it, have no doubt.”  [This is Hooke’s Animadversions on the first part of the Machina coelestis of Hevelius (1674), in which Hooke attacked Hevelius’ naked eye measurements of stellar positions and advocated the use of telescopic sights on measuring instruments.  This was the great controversy between Hooke and Hevelius which lasted for many years.  The tract did, in fact, not appear until several months later:  the Royal Society’s Council licensed it for the press on 9 November and it was discussed in the December issue of the Phil Trans.].

2.     “In order to comply with your letter,…I took pains that an excellent microscope was procured for you, which you will receive herewith…It is provided with six objectives, as you wished, but only two oculars, since our most skilled opticians prefer these two to three, which will, no doubt, also be proved by you through experience.”

Oldenburg also sends two books:  Boyle’s De hypothesis mechanicae excellentia et fundamentis considerationes quaedam [1674], [which is a Latin translation of the excellency and grounds, published earlier that year]; and John Mayow’s Tractatus quinque medico-physici [1674].

            The books and microscope together cost 12 pounds sterling.  But this will be offset by the income from the sale of Machina coelestis in London. 

            He mentions again that he has sent a package with books by Boyle and Wallis.

            There is some discussion about packages to and from Ismael Boulliaud in Paris.  [Apparently Oldenburg was acting as an intermediary].  A certain Captain Smith had acted as a carrier, but he had died near the end of 1672, and now Oldenburg cannot remember the details exactly.  [All these complications were, of course, largely due to the war with the Dutch; see Oldenburg, 10, Introduction].

            Hooke’s Animadversions have not yet come off the press.

            [Hevelius had apparently asked what the chances were of having English sailors make observations of the stars near the South Pole.  Oldenburg answers]:

            “It will be most difficult to obtain for you the observations of stars situated near the South Pole.  The English may organize voyages to South America or Africa, but it is hardly to be hoped that sailors will want to take pains in this so that we may obtain from them accurate observations such as are needed.  The The most recent eclipse of the moon was not observed in England.  Perhaps people in other places had more luck.  Oldenburg believes that in Paris Cassini and Huygens are trying Hooke’s method of determining annual parallax [see above, Hooke’s Attempt…].  Time will teach with what result.

 

The Correspondence of Henry Oldenburg is now published through 29 April 1674 old style, i.e., 9 May 1674 new style), in Vol. 10. 

 

The last letter printed in that volume is from Hevelius to Oldenburg, 9 May 1674 (n.s.).  In a note to this letter, the editors, Rupert and Marie Hall, write:

 

“…from some reason [Oldenburg] appears not to have kept a copy of any letter he may have written after these letters were read to the Society on 23 April 1674, nor has any original survived.  It is difficult to account for this mysterious and atypical silence, which extends to the present letter, endorsed as received 17th May [o.s.].”

 

“I don’t know how long this silence went on, but it may just mean that these two Oldenburg letters are unknown.  Volume II should appear soon, and this should answer that question.” - Albert van Helden.

 

3.  This is a reply to Aston’s letter of 20 February 1684 (o.s.).  Hevelius had put off the reply until he had something to send.

 

“Given this convenient opportunity, and having published my little work of observations, namely Annus Climactericus, I did not want to neglect my duty any longer, but to offer it duly to you and the Royal Society…Humbly asking that you will receive, in good spirit and in love of truth, these little pages…, written in defense of my observations, and that you, moreover, deem the author worthy of your protection against all envious persons and those wishing me ill.  In the said little work you will not only see discussed that controversy between Hooke and me long ago conducted with mere words and [more recently] when Halley was here (whom the Royal Society sent to me at the end of 1679) clearly and with the eye [itself], but you will also find may observations of planets as well as occultations and eclipses, made by me here in Gdansk [Danzig] in my new observatory, after that abominable misfortune of mine.”  [The abominable misfortune was the fire which destroyed Hevelius’ observatory and many of his books.  The Annus Climactericus is his defense of naked-eye measurements of stellar positions].

 Royal Society has not yet returned [from its summer recess] to its meetings, but as soon as this happens I shall not forget to put your request before them.”  [This may be the first mention of a project which led to Halley’s trip to St. Helena, 1676-1678.  Incidentally, Birch does not show any mention of such a project in the autumn meetings of the Royal Society that year].

 

In return, Hevelius asks to be sent new works “in mathematics and philosophy” which may have appeared recently, especially the Phil. Trans. since July 1683.  [Obviously contact with the Royal Society was now considerably less frequent than it had been in the days of Oldenburg].

 

Besides the copies for Aston and the Society, there are twelve to be disposed of as follows:  two for John Wallis, together with an enclosed letter, one each to the University of Cambridge, John Greaves, Edmund Halley, John Flamsteed, and Mr. Cluver.  The remaining five copies can be sold at 7 shillings to whomever Aston wishes.  The receipts of this will offset the cost of the Phil. Trans. issues requested.  [Note that Hevelius did not give Robert Hooke a copy.].

 

4.  Hevelius has received Aston’s letter of 9 February 1685 (o.s.), but the announced books, Backer’s Clavis algebrae [?], Boyle’s Experiments and considerations about the porosity of bodies [1684], and Plot’s De origine fontium [1685], have not arrived.

 

He has received nine books:  Thomas Burnet’s Telluris theoria sacra [1681, but perhaps the English edition of 1684], books by Vossius, Lister and Goddart on mineral waters [of these I have only been able to identify Martin Lister’s De fontius medicatis angliae, 1685], Isaac Barrow’s Lectiones [either Lectiones habitae in scholis publicis Academiae Cantabrigiensis of 1684, or its reissue entitled Lectiones mathematicae of 1685], Thomas Lydiate’s Canones chronologici [1675?], Boyle’s Short memoirs on the natural experimental history of mineral waters [1684?], and William Briggs’ Nova visionis theoria [1685].  He send his thanks for these.

 

[Apparently Aston had written that Annus Climactericus had been well received, (which was a white lie) for Hevelius writes]:  “I am especially pleased that that little work of mine, Annus Climactericum was received by all friends, as well as by the Royal Society, with such a serene countenance…”

 

He is encouraged by this to press on and finish by the next summer his Uranographia and his Prodromus together with his new catalogue of fixed stards. 

[The Prodromus was published posthumously by his wife].

 

He has some information on the recent lunar eclipse and hopes to see the observations of Flamsteed and others of this event in the Phil. Trans.

 

He sends greetings to the University of Cambridge, from which he has received a letter, and to John Wallis, whose letter he will answer at a better opportunity.  [Presumably both letters were to thank Hevelius for copies of his Annus Climactericus].  Greetings also to Flamsteed, Cluver, and Halley, and other friends [to whom he had sent copies of Annus Climactericus], but why hasn’t he had responses from them?  He asks Aston to find out the reasons for this and, should letters have been lost, to obtain copies for him. The remainder is a New Year’s wish and greeting to his friends and the Royal Society.

 

            The Two Letters to Francis Aston, Secretary of the Royal Society, are drafts or copies in Hevelius’ hand.  The first one, dated April 1685, was perhaps never sent, or if it was sent, it was not received.  Birch shows no letter of Hevelius being read in 1685 before the meeting of 10 June (Birch 4, 406):

 

“A letter of Mr. Hevelius to Mr. Aston, Dated at Dantzick May 19 1685 N.S. was read, giving notice, that he sent several copies of his Annus Climactericus, newly printed.”  This letter is printed in MacPike, Halley, 197.

 

The letter dated 29 December 1685 was read at the meeting of 20 January 1685/6(o.s.), see Birch 4, 452.  Only one further letter from Hevelius was read before the Society, his letter of 17th April 1686, read 24 November 1686 (o.s.).  There is no mistake about the year of Hevelius’ first letter here, for the letter of 17 April 1686 is quite different in content from that of April 1685.

 

Conclusion

 

The Two Letters from Henry Oldenburg, the eminent secretary of the Royal Society to Hevelius together with the Two Letters written by Hevelius to Oldenburg’s later successor as secretary, Francis Aston, represent a vivid picture of the great strides made in science, especially in astronomy, in the late seventeenth century.  They also stress the importance of the distribution of scientific information and the observations made and imparted through correspondence between  Hevelius and the Royal Society.

 

This correspondence is of special interest in relation to the Hooke and Hevelius controversy.  H. C. King writes that “Hooke argued that while he could measure with a telescope an angle of 1 second, the minimum angular separation given by a normal eye was, at the most, about 30 seconds and more generally, only 1 minute.  Unless two stars were separate further than this amount, they would appear as one.  Hevelius did not deny this.  He claimed, however, that good eyesight and long practice had enabled him to exceed these limits.  In proof, he sent a set of measures to Hooke, requesting him to check them with his own instruments…  These remarks, and others like them, received the strong and tactless censure of Hooke in his retaliatory Animadversions… Hooke passed over Hevelius’ optical difficulties but ridiculed his instruments and slighted the value of his observations.  ‘This’ Molyneux writes, ‘did but exasperate the Noble old Man, and made him adhere more obstinately to his former practice’ … Eventually, the dispute became so heated that the Royal Society intervened and, in 1679, sent young Halley to Danzig to ease the tension.  Hevelius received him warmly, and the two astronomers, one at the beginning and the other near the end of his career, made and compared observations.  Halley found that Hevelius’ claims were justified, but he could not convince his host of the greater accuracy of the telescopic sight.  Even after this, a further passage of arms ensued between Hevelius and Hooke in 1685, but to the gain of neither…” - The History of the Telescope.  pp.  100-101.

 

See also:  Wolf, A History of Science…:I, pp.  182-83.

 

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