Showing papers in "Journal for the History of Astronomy in 1986"

Atmospheric Extinction Effects on Stellar Alignments

Abstract: The extinction angle is the lowest angle on the horizon at which a star is visible. In other words, if the star were any lower on the horizon than the extinction angle, then the increased amount of atmospheric scattering and haze would render the star invisible. It should be noted that the value of the extinction angle can vary from place to place and from night to night. In this paper, the extinction angle will be measured from the zenith and will be denoted by z. The determination of extinction angles is an important problem for archaeoastronomy, because z is usually needed for calculations regarding the azimuth of proposed stellar alignments: errors in the value of z will translate into errors in azimuth of the first or last sighting of a star. In many practical cases, the error in azimuth is greatly magnified from the error in z by the low angle at which stars may rise relative to the horizon. Hence, a thorough understanding of extinction angles is required to discover and assess any stellar alignment. There have been many studies of models of extinction as a function of zenith distance, which is an important quantity in modern astrophysical photometry. There is a survey of much of this earlier work in Schoenberg (1929), including a reference to an interesting study by Muller (1891) of extinction at all zenith distances up to 89 from both low and high altitude observing sites. Unfortunately, to the best of my knowledge, no accurate model of extinction angles as defined in this paper has ever been proposed; and worse, no actual observations of such extinction angles have ever appeared in the literature. In this paper, I seek to fill these gaps with a three-part approach. In Section 2, I will present numerous observations of extinction angles for objects ranging between -2.7 and 5.4 magnitudes (m). In Section 3, I advance a quantitative and modern astronomical model for predicting z. In Section 4, I analyse the statistical errors associated with the azimuth of a star's first appearance. The results from these sections are then applied to a wide variety of claimed stellar alignments.

The Greenwich List of Observatories: A World List of Astronomical Observatories, Instruments and Clocks, 1670–1850

Abstract: When the publication of the General history ofastronomy was being planned, it was realised that basic historical data on observatories and their instruments for the period from 1670 to 1850(when vol. iii ends) had never before been gathered together. The Greenwich List of Observatories (GLO), which was to detail major astronomical instruments and clocks, observatory by observatory and country by country, was therefore launched at a meeting of Commission 41 (History of Astronomy) of the International Astronomical Union in Grenoble, France, in August 1976. The response was overwhelming. Since that date, scholars from 28 nations their names are listed below on p. iv have sent me data on some 230 observatories worldwide. It is hoped to include the essentials of these data in the Generalhistory of astronomy itself, but, as a preliminary measure, a fuller though necessarily imperfect version is published here. The layout and selection of data have been chosen to reflect the fact that weare interested here primarily in observatories, rather than the instruments for their own sake: with the GLO the reader will be able easily to establish the calibre of the observatories in a given country at a given period. For the most part we are concerned with the major instruments of each observatory, which we define in general as those onfixedmountings but here weallow ourselves some latitude in the seventeenth and eighteenth centuries, in order to include observatories that were considered important in their day even though they had no fixed instruments. Furthermore, what constitutes a major instrument is somewhat date-dependant, as a similar instrument could be major in the seventeenth century but minor in the nineteenth. So that a definitive version can one day be published, I would warmly welcome data to correct errors and omissions. Please send them to me: H. Derek Howse, 12 Barnfield Road, Riverhead, Sevenoaks, Kent TN 13 2AY, England; telephone (0732) 454366.

J. C. Kapteyn and the Early Twentieth-Century Universe

Abstract: With only a few recent exceptions, scholarly literature in the history of astronomy has generally emphasized planetary astronomy to the neglect of developments in stellar astronomy.1 Within the broad field of stellar astronomy, the sub-discipline of 'statistical astronomy' has been among those areas that have fallen victim to this tendency.' Yet this sub-discipline has been of great importance, for during the first several decades of this century astronomers generally believed that a statistical approach to analysing the aggregate of stars would eventually lead to an accurate understanding of the architecture of the stellar universe. Although William Herschel initiated this program in the late eighteenth century, it was not until a century later that it began to achieve promise with the work of two prominent astronomers, J. C. Kapteyn (18511922)and Hugo von Seeliger(1849-1924). From about 1890until roughly 192.0, Kapteyn and Seeliger shaped astronomers' views of the stellar universe. To understand the stellar universe through the use of statistical techniques, referred to as the \"sidereal problem\" in much of the technical literature, was considered the major research program of stellar astronomy during much of the period considered here. It is the purpose of this paper to examine Kapteyn's contributions to this field of astronomy during the three decades prior to the \"astronomical revolution\" of the 1920s. Kapteyn was motivated principally by his life-long desire to understand how the stars were distributed and arranged in space. Many of the methods he developed to investigate the complexities of the Milky Way system have become fundamental. The techniques he used and the provisional models of the stellar system he obtained provided astronomers with tools and concepts needed to explore with increasing success the Milky Way system. All of his efforts, including those directed towards his organization of star catalogues, and his work in the field of international diplomacy, were motivated by this one great, astronomical project. In what follows, we will focus principally on two developments: (1) Kapteyn's studies of systematic stellar motions, and (2) his analysis of the sidereal problem. Equally significant for the development of astronomy, Kapteyn's interests in the Milky Way directly shaped the contributions of several generations of his students. Willem de Sitter, H. A. Weersman, Pieter van Rhijn, and through van Rhijn, Jan Oort, Bart Bok and others, made fundamental advances in modem astronomy. As Bok has recently reminisced in an oral interview for the American Institute ofPhysics: \"In astronomy, I think we [the Dutch] all derived from Kapteyn. It all started with Kapteyn. Oort was Kapteyn's student. I was Oort's student. I was van Rhijn's student; van Rhijn was Kapteyn's student. Pannekoek was a great friend ofKapteyn's. So the rise of Dutch astronomy was entirely Kapteyn.'? But Kapteyn's influence extended far beyond his native Holland. Early in his career he collaborated with David Gill in the production

The star catalogue commonly appended to the alfonsine tables

Abstract: In earlier works on the history of star names! the Alfonsine Tables, or "the authors of the Alfonsine Tables", or summarily "the Alfonsinians", were often made responsible for the introduction of new Arabic material into the corpus of star names traditionally transmitted, and continuously used until today, in mediaeval Western, and modern, astronomy. Owing to the knowledge we now have of a considerably larger number of original sources, both Oriental and Occidental, and our better understanding of their historical interdependence, we are now in a position to examine and revise the judgement on the star catalogue included in the Alfonsine Tables. It may be remembered that the Alfonsine Tables were a set of astronomical tables for chronology, for the Sun, Moon, and planets, etc., accompanied by an explanatory introduction (quite in the manner of the Arabic-Islamic zfjes) , which were compiled and composed by order of King Alfonso X of Castile (reigned 1252-84). Of the Old Castilian original version of the tables made in Castile around 1263to 1276, only the introductory text has survived.s The Old Spanish text was of no major influence outside Spain. In the first decades of the fourteenth century, however, a Latin version of the Alfonsine Tables was constructed in Paris which later became the most influential handbook of practical astronomy in Europe until the sixteenth century or even later.' In what follows, when we speak of the Alfonsine Tables, we always refer to their Latin version. Like every complete zij, or work of astronomical tables, the Alfonsine Tables also contain a star catalogue. When we examine it we find at once that the star catalogue accompanying the Alfonsine Tables is nothing else but Ptolemy's star catalogue in the Almagest, in the wording of Gerard of Cremona's Latin translation made in Toledo about 1175from the Arabic, save for the values of the longitudes (in the coordinates). These were increased against Ptolemy's, for precession, by 17°8' for an assumed epoch 1252, i.e., adopting the value used in several star tables and in the complete Ptolemaic star catalogue included in Alfonso's Libros del Sabers The Alfonsine Tables proved very popular and were circulated in innumerable manuscripts. The star catalogue is included in many of these copies, but it is also transmitted separately in many manuscripts (where naturally it is easily recognized from the 'Alfonsine' longitude value, Ptolemy + 17°8').5 The popularity and dissemination of the Alfonsine Tables were certainly increased by several printed editions which, later on, became highly influential in the formation of the nomenclature of the stars. Of these editions I have examined seven: Alfontij regis castelle illustrissimi celestium motuum tabule, Venice 1483 [henceforth called at1]; Tabule astronomice Alfonsi Regis, Venice 1492 [henceforth called at2]; Tabule astronomice Diui Alfonsi Regis, Venice 1518(at the end of the book: 1521); Alfonsi Hispaniarum Regis Tabule, Venice 1524 [henceforth called at4]; Divi Alphonsi... Regis Astronomicae tabulae, Paris 1545; the same, Paris 1553 (identical in the text to the preceding edition of 1545);and

John of London and his Unknown Arabic Sources

Abstract: In my 1959 book on Arabic star names, 1 I made out a group of names which could be traced back only to an \"unbekannte Quelle\" (\"unknown source\"), but not beyond.? Some years later, it had become clear thatthe \"unknown source\" for this group of Arabic star names in Western texts was a star table established by John of London in Paris, in 1246.3 But John of London's star table offered, in its turn, several names for which no evidence in Arabic original texts or on instruments could be found. Having continued, in the years that followed, the study of related Arabic and mediaeval Western sources, I think it appropriate now to sum up and report on John of London's star table and his \"unknown Arabic source\". For the fixed stars, the basic and most comprehensive table was that incorporated in Ptolemy's Almagest, Books VII-VIII (containing 1025 stars), available to the mediaeval West since 1175 in Gerard of Cremona's Latin translation made from the Arabic.' Apart from that, for practical use on instruments, especially the astrolabe, shorter tables of basic stars (mostly containing from c. 20 to 50 stars) were drawn up in the Latin West from the late tenth century onwards, partly obtained, through translation, from Arabic sources, and partly compiled by Western authors after such translated models.! One such table was drawn up in 1246 by John of London in Paris. It contains 40 stars with ecliptic coordinates (longitude and latitude) and their magnitudes. John of London's table is ofgreat historical interest for several reasons: in itself, it is an outstanding document of astronomical observation because John has not, as many others, merely computed the coordinates by adding a constant, for precession, to the values of the longitudes in the Almagest, but he has observed all his stars per instrumentum armillarum (\"with an armillary sphere\") and thus found their coordinates by observation, which is very rare in mediaeval times.s Further, his table influenced the compilation of another star table which was appended to the astrolabe treatise of Pseudo-Messahalla and, in this context, was widely diffused.\" Eventually, partly directly and partly through the PseudoMessahalla table, John's star nomenclature became influential in modern astronomy down to our own day. John's name as the author, and the date and place of the observational work, are transmitted in the respective manuscripts, in the title of the star table.! The correctness of these indications is corroborated by a letter of John ofLondon to a certain magister R. de Guedingue in which he answers six astronomical and related questions asked by the latter.\" In one manuscript'? there is a reexamination of the star table made four years later (i.e., in 1250) with an instrument devised by an otherwise unknown Rogerus Linconus who calls himself a discipulus of the \"famous astronomer\" John of London. Fontes suggests that our John of London is identical to one Jo. Lond. sometimes mentioned by Roger Bacon.'! The letter to R. de Guedingue shows John as a learned and well-read man; among his authorities he cites: Albategni (al-Battant), Thesbith (Thabit ibn Qurra), Ptholemeus and tiber Almagesti, Abrachis (Hipparchus, in Gerard of

Failure and Success: Two Early Experiments with Concave Gratings in Stellar Spectroscopy:

Abstract: Henry Crew tried to use a Rowland concave grating for stellar spectroscopy with the Lick 36-inch refractor in 1892-93.He did not succeed. A few years later George Ellery Hale planned a similar instrument for Mount Wilson Observatory. His attempt was highly successful, although the spectrograph became quite different along the way. It is instructive to examine the differences between Crew's failure and Hale's success. Crew graduated from Princeton in 1882, and afterward studied physics in Germany for one year, attending lectures by Helmholtz, Kirchoff, and Kayser. Then he returned to the U.S. and became a physicsgraduate student under Henry Rowland at Johns Hopkins University. Crew wrote his thesis on the spectroscopic determination ofthe rotation period of the Sun as a function oflatitude. He used a large laboratory grating spectrograph, and a small, primitive heliometer to bring the solar image to the slit. The result he found, that the rotation period decreases from the equator to the pole, was contrary to the direct evidence from sunspots known at the time, and has been proven incorrect by better spectroscopic measurements since.' After earning his PhD in 1887,Crew stayed in Baltimore for one year as an assistant to Rowland, and then got a job as instructor and head of the physics department at Haverford College, near Philadelphia.? In 1891 when James E. Keeler left Lick Observatory to become director of Allegheny Observatory, Edward S. Holden hired two men, W. W. Campbell and Crew, to carryon the spectroscopic program Keeler had initiated. Holden rightly considered the spectroscopic determination of stellar \"motions in the line of sight\", (or radial velocities, as we say today) then just getting underway, the most important program of the observatory. Campbell had only an undergraduate education from the University of Michigan in engineering and in the older astronomy of position, but he had good experience in astronomical spectroscopy, for he had worked as Keeler's volunteer assistant the whole summer of 1890. Crew, the first Lick faculty member with an earned PhD, was well-schooled in laboratory spectroscopy, but had practically no astronomical training or experience. Holden wanted Campbell and Crew to work together, to complement each other's skills, but Crew refused, took his fight with the director all the way to the University of California Regents, and won. They ruled that he should be allowed to observe on his own with the 36-inch one night each week. Campbell, given two nights a week for himself, added a photographic camera to the prism spectroscope Keeler had designed as a visual instrument, and began the pioneering research that was to make him famous.' Crew started the program that he had wanted to do from the first, the application of the Rowland concave grating to astronomy.' Gratings form a spectrum by diffraction, an interference effect dependent on the wave nature of

Presentation of New Solar and Planetary Tables of Interest for Historical Calculations

Abstract: For about twenty years, historians of astronomy have been using the tables of B. Tuckerman I which give the geocentric positions of the Sun, the Moon and the five bright planets (Mercury, Venus, Mars, Jupiter and Saturn) over the period 600 to + 1649(601B.C. to A.D. 1649).Tuckerman's tablesof the Sun and planetsare based upon the theories of Le Verrierand Gaillot.! These theories have formed the basis of the Connaissance des Temps until 1984 and were among the best planetary theories available, along with the theories of Newcomb,' ROSS5 and Hill.s the basis of the Astronomical ephemeris and American ephemeris over a long period. Recently, F. R. Stephenson and M. A. Houlden? indicated thatthe accuracy of Tuckerman's tables, for the whole interval600,+ 1649,was better than 0° .05for the Sun, Mercury and Venus, about 0°.10 for Jupiter, and about 0°.15for Saturn. For Mars, the error is much more important because of a confusion, originating with P. V. Neugebauer, between Ephemeris Time (ET) and Universal Time (UT), as shown by P. J. Huber.\" Progress in the construction of planetary theories realized at the Bureau des Longitudes and at Jet Propulsion Laboratory makes it possible to plan the construction of more accurate tables than Tuckerman's for the Sun and planets, and covering a much longer period. Theories computed at the Bureau des Longitudes give the position of the Sun and planets with verygood precision over a period of 1000years. Recently, we have extended these theories for a period of 6000 years and we have constructed tables that give the positions of the Sun and the five bright planets with good precision over the period 4000,+2000.We now describe these theories and present the tables we plan to establish.

A Neglected Galilean Letter

Abstract: In 1966 I published the Italian text of a long astronomical letter as \"reasonably attributable to Galilee\".' Left undated and unsigned, it was written by Galileo at the Tuscan embassy in Rome where he was awaiting trial by the Inquisition on grave suspicion of heresy. Evidence for this willbe presented here. Crucial parts of the evidence were unknown to me in 1966, and the letter has lain neglected until now. Its interest is threefold: it demolishes the belief that Galileo was in any significant sense a Platonist: it throws light on his scorn for the Tychonic system; and it explains his neglect of the Keplerian elliptical orbits of planets. The letter (see Figure I), to be translated below, occupies five pages, four pages formed by folding a full sheet plus a half-sheet, on the final side of which are the words \"P.re Abbate Lanci\" in a hand different from that of the letter. The letter is in Galileo's hand, in my opinion, and both sheets are watermarked as are four signed and dated letters of his written in March-April 1633.2 Its salutation, \"Ill.mo mio Sig.re\", shows it to have been written to a layman, whom I believe to have been Filippo Magalotti. A reason for writing it was given, that it might serve \"il mio caso\"; Galileo was the only Italian astronomer concerned about a case, in the legal sense. In the letter is an allusion to Kepler and two quotations from William Gilbert's De magnete, both of them authors mentioned in Galileo's Dialogue and seldom cited by other Italian astronomers of the period. The style is informal, though technical astronomical matters are considered, in accord with Galileo's writings. Finally, a statement is made in connection with the Tychonic system that I believe to contain an item of information known only to Galileo; Kepler may have noticed it, but hardly any Italian except Galileo. Magalotti, if I am correct, proposed a question to Galileo on behalf of the author of a Latin composition without disclosing his identity. Only a few brief passages are quoted from it in the letter, but its subject is evident; the author believed he had found the archetypal reason for the obliquity of the ecliptic. Galileo was asked his opinion of this. The author was Abbot Giovanni Maria Lanci. That Galileo was unaware of his identity is clear from references to him as \"the Author\", \"this Gentleman\", and \"the Proponent\", lacking any clerical title. Lanci was probably in Rome at the time, and received his Latin composition back, together with the letter, on which Magalotti had noted his title and name. I have reason to believe, though I am not certain, that the letter was found about a quarter-century ago in the vicinity of Fano, Lanci's native city. Galileo's situation at the time entailed a certain risk if he signed any discussion of astronomical matters in which Copernicans were mentioned. No signature was necessary for Magalotti or for the author who wanted Galileo's opinion. To date and sign the letter might result in a copy, accurate or altered, coming into the hands of a hostile person interested in Galileo's case. The letter is complete except as to date and signature, omissions that I regard as deliberate in this instance. Filippo Magalotti was of a distinguished Florentine family that had many

Scepticism and French Interest in Copernicanism to 1630

Abstract: France was.unusually late in prod ucing a committed advocate of heliocentrism. It alone among the major nations of western and central Europe had none before the seventeenth century. Perhaps this was a consequence of the fact that France had no tradition of technical astronomy in the sixteenth century. Pierre de La Ramee (Ramus) can be regarded as the only well-known writer on astronomy in France in that period.' Nonetheless, Frenchmen in numbers much greater than is usually noted for the era before Descartes revealed themselves in print as having an interest in Copernicanism.! Lacking strength in technical astronomy, whydid the French intellectual community find it useful to cite the Polish astronomer? It is the thesis of this paper that philosophical scepticism and one of its offshoots, fideism, were significant factors in creating interest in the heliocentric theory among the French intellectuals. Certainly it is the nature of sceptics to refuse to commit themselves to any idea, and especially not to an untested hypothesis; but the heliocentric theory had a strong attraction for many, not as an explanation of the universe but as a challenge to established thought. As one sceptic put it, Copernicus used beautiful demonstrations to show that the Earth moves despite the contrary evidence of the human senses. As Richard Popkin, Charles Schmitt, Nicholas Jardine, and others have demonstrated, the mid-sixteenth century saw a strong upsurge in interest in several modes of scepticism, particularly in France. Popkin in his works has emphasized the reappearance of Pyrrhonian scepticism, promoted in large part by the printing of the works of the ancient sceptic Sextus Empiricus in 1569.3 Pyrrhonism was the point of view that the human mind was incapable of being certain about anything: "I don't know what I know." Schmitt has examined academic scepticism, which more emphatically insisted on the inability of the human mind to know anything.' "All I know is that I know nothing." Numerous printed editions of its main text, Cicero's Academica, appeared in the sixteenth century, including one by the Frenchman Omer Talon in 1547. Jardine has concentrated on a type of scepticism more directly associated with scientific thought the opinion that the mind was unable to understand the nature of the heavens.! In this view, which found a very influential sixteenth-century voice in Andreas Osiander's unattributed preface to Copernicus's De revolutionibus orbium celestium (1543), astronomical hypotheses could neither be proven nor disproven. Astronomers were to restrict themselves to calculating the movement of the heavenly bodies. With two or three exceptions none of the French authors considered in this paper was concerned with this last type of scepticism. Their concerns were with the broader epistemological question of what the mind was capable of knowing and with their often very belligerent attack on the Aristotelian tradition.

The Interrelationship of Rock Art and Astronomical Practice in the American Southwest

Abstract: In recent years researchers have made various claims that indigenous peoples in the American Southwest used rock art to record astronomical phenomena. The bases for such claims range from postulated rock art depictions of the supernova explosion of A.D. 1054 that resulted in the formation of the Crab Nebula to the idea that petroglyphs were carved and positioned to interact with light and shadow phenomena at calendrically significant times of the year. This paper reviews the nature of the evidence presented, in the context of the anthropology and ethno-archaeology of contemporary and prehistoric Southwestern peoples, and suggests directions for future research.

The Length of the Year in the Original Proposal for the Gregorian Calendar

Abstract: In a note! published in this journal in 1974 I considered the origin of the length of the year in the Gregorian Calendar, concentrating in particular on the earliest proposal by Petrus Pitatus in 1560for the year eventually adopted in the reformed calendar, the general principles of which are usually attributed to Aloysius Lilius. At the time I had not seen the proposal of 1577, the Compendium novae rationis restituendi calendarium, that preceded the adoption of the calendar in 1582,and as I mistakenly believed that no copies ofthe proposal survived I made no attempt to consult it. In fact, as I have since learned, some few copies of the original 1577 printing do survive, but more to the point, the text has always been readily available in countless libraries since it is printed in Christopher Clavius's comprehensive treatise on the calendar, originally published in 1603and reprinted in vol. v of the 1612edition of his Opera mathematica.l I have recently examined the 1577 proposal as reprinted eisdem prorsus verbis, as Clavius says, in the 1612 edition, and found that it contains an interesting alternative plan for intercalation, taking account, after a fashion, of the variable tropical year of Copernicus. The plan was not adopted, for very sensible reasons, but does show that the possibility of incorporating the most up-to-date, although questionable, astronomy was at least considered. The 1577 proposal actually contains four different plans for intercalation. First come two that follow the adopted plan for omitting three out of four centennial leap years, but differ in their procedure for the initial adjustment of the date of the calendrical equinox to 21 March. The next two follow the plan for a variable intercalation depending upon the variable length of the tropical year, and likewise give two versions for the two ways of initially adjusting the equinox. Before considering these, we shall briefly review the substance of our earlier note. The version of the calendar adopted in 1582 uses the following intercalation: (I) A common year contains 365 days, a leap year 366 days, the extra day being added to the end of February. (2) Every year of the Christian Era (A.D.) after 1582 divisible by 4 is a leap year (3) except centennial years, which are leap years only if divisible by 400. From (3) it follows that A.D. 1600is a leap year, 1700, 1800,and 1900are not, and 2000 will be a leap year. Consequently, there are 97 additional-days in 400 years, and the mean length of the year is 365 97/ 400 days. Further, the calendrical vernal equinox was moved to 21 March, its date at the time of the Council of Nicaea in 325, by omitting 10 days, from 5 to 14 October, of 1582. The plan of omitting three out of four centennial leap years was earlier proposed by Pitatus, who, however, would have begun the omission in 1600-so 1600,1700, and 1800would be common years and 1900a leap year-and would in addition have moved the calendrical equinox to 25 March in a common year and 24 March in a leap year, as in the time of Julius Caesar and Christ.' Pitatus

Archaeoastronomical Research in Veneto-Friuli, Italy

Abstract: Archaeoastronomical research in the Veneto-Friuli region of northern Italy (Figure I) was begun in 1979and some papers already have reached press in this field. I The aim of the research has been the identification of alignments between various structures associated with prehistoric and protohistoric monuments or between the monuments found in the region that might have been correlated with the directions of astronomical phenomena at the horizon. There are several reasons to anticipate the use of astronomical sighting schemes in Italy, and therefore, to determine through accurate astronomical observation the degree to which alignments might be related to the principal dates of the year:

Book Review: Byzantine Astronomy: Nicéphore Grégoras: Calcul de l'eclipse de Soleil du 16 Juillet 1330Nicéphore Grégoras: Calcul de l'eclipse de Soleil du 16 juillet 1330.(Corpus des Astronomes Byzantins, i.) MogenetJoseph(†), TihonAnne, RoyezRobert, BergAnne (J. C. Gieben, Amsterdam, 1984). Pp. 222. DFL 70.

Abstract: disparate sources. Few modern editors have had the stamina to do what is done here, namely, examine more than four score manuscripts in order to establish a text. The edition does ample justice to the accretions, and the numerous manuscripts in which they are found, without losing sight of the basic work. My only regret about the editions as a whole is that it eschews medieval orthography, in favour of classical (as when 'lunae' is preferred to 'lune', to take an example). By comparison with the kalendar, the text on the eclipsorium is much more straightforward, although its intrinsic interest is greater. It was the subject of a previous edition by the same editor, as indeed was the equatorium treatise of Peter of St Orner. Its author followed the procedure of astronomical tables, in that he started from mean syzygy, found the true positions of the luminaries at that time, and evaluated the time interval corresponding to their true separation, knowing their velocities. The edition contains two quadrant treatises, one by Peter of St Omer, the other previously attributed to him, but here discredited. (In fact this is a treatise that I have suggested was due to John Maudith, as is mentioned in a postscript in the edition.) The semisse is now available in an authoritative edition, as it well deserves to be, for it is an important text in the history of the equatorium, and makes a fine supplement to Olaf Pedersen's pioneer study of it, and Emmanuel Poulle's general survey of the history of equatorium. Throughout the new edition, the diagrams are clear, the indexes are full, the editing is exemplary, and as those familiar with the series Corpus philosophorum will expect, the volumes are very attractively presented and produced, and this at an extremely modest price. The price reflects support from the Carlsberg Foundation. Would that other countries had such enlightened patrons, capable of recognizing that there are more ways than one of raising the spirits. For the time being, medievalists have no moral choice when it comes to the selection of drink.

Les manuscrits delambre du bureau des longitudes

Abstract: En 1983, le Bureau des Longitudes quittait definitivement les locaux de son observatoire situe au pare Montsouris, dans le sud de Paris. A cette occasion, un grand nombre de manuscrits de la fin du l8eme siecle et du 190me siecle ont ete retrouves dans un ancien batiment depuis longtemps al'abandon. Le fonds, qui comporte environ 21000 feuillets, porte la trace d'un classement fait aux environs de 1906,mais d'apres diverses considerations, il semblerait que tous les manuscrits ayant fait l'objet de ce classement n'aient pas ete retrouves, Une partie importante du fonds actuel (plus de 9000 feuillets) est constituee de manuscrits de Delambre (1749-1822). Ceux-ci refletent les nombreux domaines d'activite scientifique de Delambre: observation, construction de tables astronomiques, mesure du meridien, enseignement, histoire de l'astronomie. Par ailleurs, nous y avons trouve un nombre assez important de lettres ou messages dont certains nous semblent presenter beaucoup d'interet. Ces lettres ou messages se trouvent melanges aux papiers de Delambre qui en a, Ie plus souvent, utilise les parties restees blanches pour ses propres calculs.