Introduction

The originals and copies of Johannes Kepler’s letters in the Bibliothèque nationale and the Bibliothèque de l’Observatoire in Paris come from the great collection of manuscripts and astronomical observations that Joseph Nicolas Delisle brought together between 1709 and 1750, as astronomer of the Paris Observatory, on his travels through Germany and during his stay in Russia.¹ An important part of this collection is formed by the observation journals that he acquired at Danzig and the far-reaching correspondence of Hevelius, which still awaits close study.² Delisle also tried to obtain Kepler’s papers, which had passed in 1708 from the heirs of Hevelius to Hanschius and were at that time, 1736, still in Vienna; but his efforts came to nothing. He did, however, acquire a very interesting correspondence addressed to the Leipzig physician and astronomer Philipp Müller, which, besides letters from the chronologer Sethus Calvisius and the Danzig astronomer Peter Crüger, contains a number of letters from Kepler and others from Kepler’s son-in-law Jacob Bartsch. Copies were made at the time (probably while still in Germany) of some of the more important letters and added to the collection.

After his return to Paris, Delisle handed over his whole collection on astronomy and geography to the State in return for a life annuity and the title of Astronome de la Marine.

About 1750 the collection was incorporated into the Dépôt de la Marine, which is why the manuscripts still bear, unless it has been forcibly removed, a green stamp: an anchor with three lilies and the legend “Dépôt des cart. pl. et journ. de la Marine”. In 1795 the Comité de Salut public ordered the manuscripts transferred to the newly founded Bureau des Longitudes, from which they were soon afterwards handed over to the Bibliothèque de l’Observatoire de Paris, then being formed.

When, in the 1840s, G. LibriGuglielmo Libri (1803–1869), mathematician and inspector of French libraries, who stole thousands of manuscripts from them. made his ruinous raids, bound up with forgeries, through the libraries of France, he plundered the library of the Paris Observatory too. Along with part of the manuscripts of Hevelius, Kepler’s original letters and some of the copies were stolen from there. Some of these pieces, original letters of Kepler and copies, came to England with the great collection of manuscripts and printed works that Libri secretly sold to the Earl of Ashburnham in 1847. After the Earl’s death in 1878, when his son put his father’s precious library up for sale, the Bibliothèque Nationale set about buying back the treasures stolen in France: besides the so-called “Fonds Libri”, these included the objects of the Fonds Barrois, acquired by the Earl of Ashburnham in 1849. Both collections were bought back in 1888.³

The letters of Kepler that came to the National Library through this repurchase are contained, with other manuscripts of the Delisle collection, in Codex no. 1635 of the “Nouvelles acquisitions latines”. The “Correspondance de Hévélius” (Nouvelles acq. lat. Cod. 1639–1642) also contains (in Cod. 1640) a “projet d’un recueil des oeuvres posthumes de Kepler” by Hevelius, headed “Opera posthuma praeclarissimi et acutissimi Joh. Kepleri ex bibliotheca Heveliana edenda”, to which I shall return when discussing other lists of Kepler’s manuscripts.

The documents still at the Observatoire (the copies of five letters of Kepler) are contained in fascicle no. 89 of Delisle’s original list, which under Delaunay’s new cataloguing of 1871 bears the shelfmark

B, 1 9. 89. “Lettres de Sethus Calvisius, Jean Kepler etc. 1612—1635. Lettres écrites à G. Kirch 1674—1709. 1 portef. in Fo.”⁴

If we now put together the letters of Kepler in the Bibliothèque Nationale and those in the Observatoire, it turns out that, with one single gap, either the originals or at least copies survive of all the letters of Kepler that Delisle originally acquired.

For of the letters that Delisle gathered at the time in fascicle 89, the parts each with its own cover,

89, 5; 89, 10; 89, 7; 89, 8 and 89, 9

form precisely that correspondence addressed to Philipp Müller which Delisle had acquired in Germany.⁵

This correspondence bears a numbering 1, 2, 3 … 50, evidently made before Delisle acquired it, at the bottom centre of the front of each letter. Beside this, the letters and covers also bear the shelfmark Delisle added (at the bottom left of the front of each piece): the letters A (in each case for the cover), B, C … added to the part numbers 89, 5; 89, 10 and so on. The letters of Kepler filed under 89, 7 and 89, 8 are in each case followed by the copies made of them; the other letters exist only in the original. Since, moreover, each cover records the sender and recipient of the letters and the number of pieces filed in it, a list can be drawn up of the letters and copies originally and now present, from which we can judge how complete Kepler’s letters are.

The result is the following list, arranged by the original numbering 1, 2 …:

List of the collection of letters to Philipp Müller, Licentiate of Medicine and Professor at the University of Leipzig, from the years 1612–1635, acquired by Delisle about 1736.⁶

89, 5. “Lettre de Sethus Calvisius de Leipzic, le 5 mars 1612 à l’academie de Leipzic. Deux pièces cottées compris l’envelope.”
Original in the Bibliothèque de l’Observatoire.

89, 5. A. Cover.
89, 5. B. 1. Letter from Sethus Calvisius, on the question of the calendar.

89, 10. “Lettres de Jac. Bartschius à Philippe Müller. Les années 1629, 1630 et 1632.”
“Neuf pièces cottées, compris l’envelope.”
Originals, all in the Bibliothèque de l’Observatoire.

89, 10. A. Cover.
89, 10. B. 2. Letter from J. Bartsch to Ph. Müller. Dated Lauban, 30 April 1629.
89, 10. C. 3. Letter from J. Bartsch to Ph. Müller. Dated Lauban, 29 July/8 August 1629.
89, 10. D. 4. The same. Dated Lauban, 9/19 January 1630.
89, 10. E. 6. [!]⁷ The same. Dated Sagan, 7/17 November 1630.
89, 10. F. 7. The same. Dated Sagan, 3 January 1631.
89, 10. G. 8. The same. Dated Lauban, 5 May 1631.
89, 10. H. 9. The same. Dated Lauban, 19/29 June 1631.
89, 10. J. 11. [!] The same. No place given, dated 3 Sept. new style 1631.

89, 7. “Lettre de Jean Kepler à Jean Seussius, secretaire de l’electeur de Saxe, du mois Juillet 1622.”
“it. Une autre lettre de Kepler sans datte n’étant pas non plus marquée à qui elle est addressée avec une copie des mesmes.”
“Cinq pièces cottées, compris l’envelope.”
Originals and copies, all in the Bibliothèque Nationale except the cover (A), which stayed at the Observatoire.

89, 7. A. Cover with the heading above.
89, 7. B. 12. Letter from J. Kepler to J. Seussius. No place given, dated 1 July 1622. Original Nouv. acqu. lat. Cod. 1635. Fol. 92, 93.
89, 7. C. 13. Letter from J. Kepler [to Ph. Müller]. Addressee, place and date missing. Original Nouv. acqu. lat. Cod. 1635. Fol. 102. 103.
89, 7. C. 14. “Postscripta [to the preceding letter]”. Addressee, place and date missing. Original Nouv. acqu. lat. Cod. 1635. Fol. 104.
89, 7. D. Copy of the letter to Seussius. B. 12. Nouv. acqu. lat. Cod. 1635. Fol. 94, 95.
89, 7. E. Copy of the “Postscripta”. C. 14. Nouv. acqu. lat. Cod. 1635. Fol. 105–108.

The letter to Seussius, B. 12, has not been published until now. The letter C. 13 is known from a draft in Kepler’s hand in the first volume of the Kepler manuscripts kept at the Pulkovo Observatory. Hanschius included the letter, from this manuscript, in his collection “J. Keppleri aliorumque Epistolae mutuae”, pp. 698–704.⁸ It is addressed to Philipp Müller and answers a letter of Ph. Müller dated Leipzig, 3 August 1622, printed in the Epistolae mutuae, pp. 695–698. The letter to Seussius mentioned in these two letters is precisely the letter B. 12 above, dated 1 July 1622.The letter itself is dated Idibus Iuliis, the Ides of July: 15 July 1622. The Paris manuscript of Kepler’s letter to Ph. Müller lacks some sentences of the text printed by Hanschius, and the final pages, about half the letter. To hide the missing final page, a strange hand (Libri’s?) has added at the foot of the last surviving page (fol. 103 in the numbering of the codex), as a catchword, “Abrahamo”, the first word of the “Postscripta” on the following page of the manuscript (fol. 104 of the codex).

89, 8. “Lettres de Jean Kepler à Philippe Müller. Les années 1629 et 1630.”
“Avec la copie de la plupart.”
“Quinze pièces cottées, compris l’envelope.”

89, 8. A. Cover, bearing the heading above. Bibl. Nat. Nouv. acqu. lat. Cod. 1635. Fol. 91.
[89, 8. B. 15. Letter from J. Kepler to Ph. Müller. Dated Sagan, 17/27 October 1629. Original missing.]
[89, 8. C. 16. The same. Dated Sagan, 13/23 November 1629. Original missing.]
[89, 8. D. 17. The same. Dated Sagan, 4 January 1630. Original missing.]
[89, 8. E. 18. The same. Dated Sagan, 16/26 January 1630. Original missing.]
89, 8. F. 19. Letter from J. Kepler to Ph. Müller. Dated Sagan, 27 February 1630. Original Bibl. Nat. Nouv. acqu. lat. Cod. 1635. Fol. 98.
[89, 8. G. 20. The same. Dated Sagan, 22 April 1630. Original missing.]
89, 8. H. 21. Letter from J. Kepler to Ph. Müller. Dated Sagan, 26 August 1630. Original Bibl. Nat. Nouv. acqu. lat. Cod. 1635. Fol. 100. 101.
[89, 8. J. 22. The same. Dated Lauban, 2 September 1630. Original missing.]
89, 8. K. Copy of B. 15. Bibliothèque de l’Observatoire.
89, 8. L. Copies of C. 16; H. 21; J. 22. The same.
89, 8. M. Copy of D. 17. The same.
89, 8. N. Copy of E. 18. Bibl. Nat. Nouv. acqu. lat. Cod. 1635. Fol. 96.
89, 8. O. Copy of F. 19. The same, fol. 97.
89, 8. P. Copy of G. 20. The same, fol. 99.

89, 9. “Lettres de Petrus Crugerus à Philippe Müller. Les années 1620—1635.”
“Vingt-huit pièces cottées, compris l’envelope.”

These letters bear the numbers 24–50 of the original arrangement. Delisle gave them the shelfmarks 89, 8. A. (cover), 89, 9. BSic. Read 89, 9. A.: the Crüger letters' cover. to 89, 9. Z (leaving out V), then 89, 9. Aa to 89, 9. Dd. The series is complete except for number 43 (between September 1632 and February 1633). Between the two series of letters 89, 8 and 89, 9, number 23 is missing, of which I have been able to find no trace in the whole fascicle B. 1, 9 of the Observatory library.

Delisle’s collection of letters thus contains 10 letters of Kepler, in originals or copies.

The letters B. 12 and C. 14, addressed to Seussius and Ph. Müller and surviving in original and copy, belong together in time and content, and complete the letter C. 13, already known from Hanschius, of which the Paris manuscript has only a fragment.

The other 8 letters, addressed to Philipp Müller in 1629 and 1630, two of which survive in original and copy and the rest only in copy, are likewise connected with each other and probably form an unbroken series. Some letters of Jac. Bartsch to Ph. Müller also fit into it by their content; but they go on beyond the year of Kepler’s death (November 1630). We give them, like some letters of P. Crüger to Ph. Müller, in extracts in the following appendix (C, I), so far as they concern Kepler.

Finally we add, also in extracts, a letter not published until now, which J. Bartsch addressed to Kepler in the autumn of 1628 and placed at the front of his “Ephemeris nova Tychonico-Kepleriana” for 1629 (Lipsiae 1629). Kepler put his answer to this letter at the front of the new edition of these ephemerides (Sagan 1629). It is printed in the Opera, vol. VII, pp. 581 ff. Both letters complete the picture, given by our eight letters to Ph. Müller, of the circumstances in which Kepler found himself in the last years of his life.