Scientific Instruments and Museums: Proceedings of the XXth International Congress of History of Science (Liège, 20-26 July 1997) Vol. XVI (de Diversis Artibus) 2503513697, 9782503513690

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SCIENTIF IC INSTRUMENTS AND MUSEUM S

DE DIVERSIS ARTIBUS COLLECTION DE TRA VAUX

COLLECTION OF STUDIES

DEL' ACADEMIE INTERNATIONALE

FROM THE INTERNATIONAL ACADEMY

D'HISTOIRE DES SCIENCES

OF THE HISTORY OF SCIENCE

DIRECTION EDITORS

EMMANUEL

ROBERT

POULLE

HALLEUX

TOME 59 (N.S. 22)

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BREPOLS

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PROCEEDINGS OF THE XXth INTERNATIONAL CONGRESS OF HISTORY OF SCIENCE (Liege, 20-26 July 1997)

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VOLUMEXVI

SCIENTIFIC INSTRUMENTS

AND MUSEUM S

Edited by

Maurice DORIKENS

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BREPOLS

BREPOLS

The XX1h International Congress of History of Science was organized by the Belgian National Committee for Logic, History and Philosophy of Science with the support of :

Banque Nationale de Belgique Carlson Wagonlit Travel Incentive Travel House Chambre de Commerce et d'Industrie de la Ville de Liege Club liegeois des Exportateurs Cockerill Sambre Group ICSU Credit Communal Ministere de la Politique scientifique Derouaux Ordina sprl Academie Royale de Belgique Disteel Cold s.a. Koninklijke Academie van Belgie Etilux s.a. FNRS Fabrimetal Liege - Luxembourg FWO Generale Bank n.v. Communaute fram;;aise de Belgique Generale de Banque s.a. Region Wallonne Service des Affaires culturelles de la Ville Interbrew L'Esperance Commerciale de Liege Maison de la Metallurgie et de l'Industrie Service de l'Enseignement de la Ville de Liege de Liege Office des Produits wallons Universite de Liege Peeters Comite Sluse asbl Federation du Tourisme de la Province Peket de Houyeu Petrofina de Liege College Saint-Louis Rescolie Institut d'Enseignement superieur Sabena "Les Rivageois" SNCB Societe chimique Prayon Rupel Academic Press SPE Zone Sud Agora-B eranger TEC Liege - Verviers APRIL Vulcain Industries

© 2002 Brepols Publishers n.v., Tumhout, Belgium

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the publisher. D/2002/0095/32 ISBN 2-503-51369-7 Printed in the E.U. on acid-free paper

TABLE OF CONTENTS

Foreword .......................................................................................................... 9 Maurice DORIKENS

Part one THE HISTORY OF GNOMONICS

Egyptian shadow clocks ................................................................................. 13 A. Sarah SYMONS Determining the Equinox in Alexandria : what were Ptolemy's rings used for? .......................................................... 21 Liba TAUB Sunlight and shadows .................................................................................... 29 Allan A. MILLS The old and the new Florentine gnomon ...................................................... 45 Carlo TRIARICO Projections geometriques et gnomonique au xv11° siecle : exemplarite et singularite de Girard Desargues (1591-1661) ........................................... 55 Didier BESSOT Medieval Islamic horary quadrants for specific latitudes : their influence on the European tradition ...................................................... 73 Maria Merce VILADRICH GRAU Le cadran astronomique, geographique et lunaire du Pere Emmanuel de Viviers (1737) suivi d'une Bibliographie gnomonique de langue frarn,;aise ..................................................................................... 109 Jean-Michel FAIDIT

Part two NATIONAL INVENTORIES OF HISTORICAL SCIENTIFIC INSTRUMENTS

Instruments, inventories and catalogues R.G.W. ANDERSON ................................................................................. 145

6

TABLE OF CONTENTS

Problems and solutions in cataloguing a University Museum ................... 153 Maurice DORIKENS and Liliane DORIKENS-V ANPRAET Cataloguing a Museum: problems and solutions ....................................... 165 Jim BENNETT Dividing the effort : an inventory of historical psychological instruments in America .................................................................................................... 171 Rand B. EVANS The directory of British scientific instrument makers and its use in research .................................................................................................... 179 Gloria Christine CLIFTON The Italian scientific instrument heritage : an impossible inventory ? ....... 191 Paolo BRENNI Instruments in Denmark, what were their origins ? .................................... 199 Jan TAPDRUP L'Inventaire du patrimoine astronomique en France .................................. 211 Fran~oise LE GuET TULLY et Jean DAVOIGNEAU

Part three MISCELLANEOUS Latin American Museums : comparative studies and links ........................ 221 Maria Margaret LOPES Inventory of the instruments belonging to Cannizzaro's laboratory in Genoa (1855-1861) .................................................................................. 237 Gabriella RAMBALDI MORCHIO Towards a new information centre in the Museum Boerhaave .................. 253 Marian FOURNIER Chemical instruments and collections from the l 9th century in the History Museum of Tartu University ................................................ 261 Leili KRUS-IL YES I Fondi Italiani di anti chi modelli e strumenti matematici ......................... 271 Franco p ALLADINO Gli strumenti e le attrezzature del Laboratorio di costruzioni della Regia Scuola di applicazione per gl'ingegneri di Torino ...................................... 287 Giorgio FARAGGIANA Measuring and dating the Arabic celestial globe at Dresden ..................... 291 Gunther OESTMANN Instruments, instrument-makers and the new physics ................................. 299 Isabel MALAQUIAS Policy and scientific instrumentation in Spain during the l 81h and l 91h centuries ................................................................ 309 Victor GUIJARRO MORA Astronomical instrument makers in Hungary between 1730 to 1830 ........ 319 Szilvia Andrea HOLLO and Lajos BARTHA

SCIENTIFIC INSTRUMENTS AND MUSEUMS

The success of the German instrument industry and the role of the Deutsche Gesellschaft fiir Mechanik und Optik .......................................... 325 JOrg ZAUN

Contributors .................................................................................................. 337

7

FOREWORD

Maurice F. DORIKENS

In this volume of the Proceeding of the xxth International Congress of History of Science the papers related to the study of scientific instruments and national inventories of scientific instrument collections are published. The interest for the study of historically important scientific instruments is growing rapidly. Not only are national collections receiving attention but also the up till now mostly hidden collections in schools, universities and other places where science was either a topic of the education programme or where research made use of very sophisticated instruments. In the past the " history of science " has predominantly been related to objects or texts seldom reaching the middle of the J9th century, but now it is clear that a tremendous amount of work has to be done to understand science and its instruments beginning in the middle of the J 9th century. The newly discovered, or should we say " dusted ", instruments from the first decades of the 201h century are sometimes scientifically exciting instruments, related to the very important discoveries in science of that period. If we do not write down the history of these instruments now, all related data will be lost. Preserving 2Qth century instruments - together with the scientific notes - should receive full attention of the " modem " science historian. The xxth International Congress of History of Science was an outstanding occasion where scholars from many countries could present their new results. We expect this volume to reflect the ideas brought forward at this Congress. The papers are published as they were accepted and presented at the conference and will therefore be sometimes written down under a condensed form. Sometimes the writing could linguistically be improved, but the congress organisers considered it more important to· publish the papers as they stand rather than spend many months on corrections.

PART ONE

THE HISTORY OF GNOMONICS

EGYPTIAN SHADOW CLOCKS

Sarah SYMONS

INTRODUCTION

Egyptian shadow clocks are small instruments consisting of a horizontal base rod of rectangular section with a vertical block at one end acting as a gnomon (fig. 1). The earliest surviving example 1 dates from the time of Tuthmosis III (1479-1425 BC). The base rod is around 20 cm long and is inscribed with five small cirles making up the hour scale. The gnomon block is missing. The most complete example2 is some 500 years younger. The base rod is around 30 cm long, and the scale markings and gnomon block have survived. The gnomon block has a hole and reference line suitable for the attachment of a plumb bob. Two indentations are visible on the top surface of the block. A further constructional element, the crossbar, was proposed by Borchardt3 in 1910. The crossbar takes the form of a rod of similar dimensions to the base rod attached at its mid-point to the top face of the gnomon block and extending horizontally at right angles to the scale. The reason for proposing this addition was to allow the time periods measured by the instrument to be seasonal hours. The augmented instrument would be used in a certain manner, being aligned exactly east-west. In the morning, the crossbar end would be placed to the east. At noon the clock would be turned 180°, so that in the afternoon, the crossbar end would be to the west. In 1965 Bruins4 explored Borchardt's theory mathematically and concluded that a set of three crossbars of differing heights would mean that the time periods measured by the clock were a very good approximation to seasonal hours. 1. Berlin Museum, 19744. 2. Berlin Museum, 19743. 3. L. Borchardt, "Altagyptische Sonnenuhren ", Zeitschrift fur dgyptische Sprache, vol. 48 (1910), 9-17; L. Borchardt, Altdgyptische Zeitmessung, Berlin, 1920. 4. E.M. Bruins," The Egyptian Shadow Clock", Janus, vol. 52 (1965), 127-137.

14

SARAH SYMONS

TEXTUAL SOURCES

The major hieroglyphic text dealing with shadow clocks occurs in relief on stone slabs which form the pitched ceiling of the Sarcophagus Chamber of the Osireion at Abydos 5 , built by Seti I (1306-1290 BC). One portion of the ceiling deals specifically with the construction and usage of the shadow clock. A diagram of a shadow clock (see fig. 2) heads the text. The symbols between the marks are the numbers 3, 6, 9, and 12, which are described in the text as being "from the Jaw". The diagram shows the marks graphically almost evenly placed on the scale, but clocks which exist to the present6 have marks separated in the 3:6:9:12 proportion, following the ratios accurately and extending the principle to a fifth mark 15 units from the fourth. The Egyptian artistic style portrays three-dimensional objects by displaying the characteristic shape of the object with other details shown above or around the main outline. The characteristic shape of the shadow clock was obviously felt to be L-shaped, but the scale markings were important and so were depicted above the main component. The addition of a crossbar would make the characteristic shape of the clock a" T ".A diagram of such a clock would probably be drawn as if looking down on the clock, with the hour marks represented on the base rod with no need to distort their position. No such diagram is known to exist. The text below the diagram is in 13 columns. The manufacture of a shadow clock is first described, followed by instructions for using the instrument. There are gaps of omission in the text. The extract presented in figure 3 concerns the usage of the clock. The problem of interpreting the text comes from the unusual vocabulary employed. The entire instrument is called a st3t. The word mr!J/ or mrbyt has been used elsewhere for " surveying instrument" in general7 but the usual form of instrument to which the word refers resembles the unadorned shadow clock in all ways but one : the lack of hour marks on the upper face of the base rod. It seems most likely, therefore, that the word should apply to the L-shaped part rather than to the crossbar. However, in the reworkings of de Buck's translation8 of this text by Parker9 , Bruins 10 and Clagett 11 , the translation of mrbyt as " crossbar" has become established. The word wpt used anatomically means 5. H. Frankfort, The Cenotaph of Seti l at Abydos, EES, 1933. 6. Berlin Museum, 19743 and 19744. 7. Z. Zaba, L'Orientation Astronomique dans l'Ancienne Egypte, et la Precession de !'Axe du Monde, Prague, 1953, 55. 8. H. Frankfort, The Cenotaph of Seti l at Abydos, op. cit. 9. 0. Neugebauer, R. Parker, Egyptian Astronomical Texts, vol. 1, 1960. 10. E.M. Bruins," The Egyptian Shadow Clock", op. cit. 11. M. Clagett, Ancient Egyptian Science, vol. 2, 1995, 467-470.

EGYPTIAN SHADOW CLOCKS

15

"top of the head", but also has the meaning of" zenith". Mrtwt is not understood at all, although Parker uses it to indicate the scale rod of the instrument. The extract indicates that the instrument needed to be aligned correctly in order to produce a reading. The act of turning the clock can be interpreted in two ways : a single 180° motion at noon, or a continuous turning towards the Sun.

A second, much later text 12 dating from the Roman period is a fragmentary papyrus showing a diagram of a shadow clock (fig. 4). The diagram appears to show the base rod of a shadow clock, with numerals 6 and 2 above it. These numbers probably represent the hour indicated when the shadow fell on that portion of the scale. The diagonal lines converge to a point now lost. The altitude of this point above the base line has been thought 13 to indicate a gnomon height greater than the block which survives on Berlin Museum 14 thus suggesting the addition of a crossbar. However, the argument is flawed due to the Egyptian style of graphically representing relationships and not proportions. Thus the nature and dimensions of the gnomon which is now lost from this papyrus can only remain conjectural. THE SHADOW CLOCK IN THE CONTEXT OF EGYPTIAN TIMEKEEPING

The place of the shadow clock in the development of Egyptian timekeeping also argues against the addition of a crossbar. The shadow clock is the earliest formal timekeeping device for finding the hour of the day from Egypt which survives to the present. It is probable that simple gnomons were used before the New Kingdom to mark periods of time during the day for such purposes as workers' shifts, but currently no object has been identified as such an instrument. Hieroglyphs depicting shadow clocks are not common, but several exist from the Ptolemaic era 15 . The crossbar appears in no known hieroglyph of a shadow clock. Only two of the hieroglyphs depict clock types of which examples have survived: Diagram (a) of figure 5 represents a shadow clock similar to the Berlin clocks, and diagram (e) represents the later type of sloping or Egyptian seasonal sundial, of which several examples survive 16. Figure 5 (b) shows a shadow clock with a curved scale. This development may have been made to facilitate the measuring of hours near dawn and sunset 12. F.L. Griffith, W.M.F. Petrie, Two Hieroglyphic Papyri from Tanis, London, 1899 (Ninth Memoir of the Egyptian Exploration Fund). 13. L. Borchardt, "Altagyptische Sonnenuhren ",op. cit. 14. Berlin Museum, 19743. 15. Valeurs Phonetiques des Signes Hieroglyphiques d'Epoque Greco-Romaine, vol. 4, Montpellier, 1990, 731. 16. An example of a complete sloping clock was first presented in: J. Cledat, "Qantarah ", Notes sur l'isthme de Suez (monument divers), Paris, 1915, 33-40 (Recueil de Travaux, vol. 37).

16

SARAH SYMONS

and seems to lead to the design of the sundial (d). Figure 5 (c) has two structures attached to the base rod, offering a possible explanation for the pair of holes on the top face of the gnomon block of Berlin Museum 17 . Without surviving examples, it is difficult to reconstruct precisely the development of the shadow clock. The hieroglyphs suggest an evolving design leading from the shadow clock to the sloping sundial. If the crossbar clock had satisfactorily measured the desired time periods it is unclear why the conservative Egyptians would have continued to adjust the design. MEASUREMENT OF SEASONAL HOURS

The addition of a crossbar to the shadow clock has been stated 18 to explain the 3:6:9:12 ratio of markings in the Osireion text and diagram. With the crossbar attached, and the clock oriented in an east-west direction, the shadow lengths produced at seasonal hour intervals are stated by Bruins to match the 3:6:9:12 ratio closely. This, however, is erroneous. Bruins' figures are obtained by finding the altitude and azimuth of the Sun on the summer solstice, the equinoxes and the winter solstice for each seasonal hour. The altitude and azimuth are then converted into shadow lengths which would be thrown by a unit high gnomon in the form of a crossbar oriented north to south. A latitude of 30°N was used and the obliquity of the ecliptic was set at 23°30'. The shadow lengths were scaled so that the fourth is 30 units long. This would be equivalent to using differing heights of crossbar according to the time of year. TABLE 1.

Markings on shadow clock (length from gnomon to mark) 0SIREION DIAGRAM

3.00

9.00

18.00

30.00

[45.00]

Seasonal hour shadow lengths WINTER SOLSTICE

4.54

9.82

17.13

30.00

65.71

% error against Osireion

33.92%

8.35%

-5.08%

0.00%

31.52%

EQUINOXES

4.64

10.00

17.32

30.00

64.64

% error against Osireion

35.34%

10.00%

-3.93%

0.00%

30.38%

SUMMER SOLSTICE

4.76

10.20

17.54

30.00

63.38

% error against Osireion

36.97%

11.76%

-2.62%

0.00%

29.00%

Comparison of seasonal hour shadow lengths with the Osireion length ratios. 17. Berlin Museum, 19743.

18. E.M. Bruins, "The Egyptian Shadow Clock", op. cit.

EGYPTIAN SHADOW CLOCKS

17

The first two rows of table 1 compare the length ratios given in the Osireion text with seasonal hour shadow lengths. Adjusting the obliquity of the ecliptic to 23°52' (an approximation for e in the epoch of 1500 BC allowing for the effects of precession) gives results for the solstices which differ very little from Bruins' findings. The greatest effect is on the longer shadow lengths, but amounts to only 0.0374% for the mark furthest from the gnomon on the winter solstice. Bruins considered only the four marks on the Osireion clock diagram, neglecting the fifth mark present on both Berlin clocks which extends the ratio sequence to 3:6:9:12:15. Setting the fourth shadow length to 30 units and ignoring the fifth mark on the extant clocks leaves only three calculated shadow lengths for comparison with the Osireion ratio. It is clear from the percentage errors (especially for the shortest and longest shadows) that the crossbar clock would not measure seasonal hours with a degree of accuracy that merits the addition of a crossbar. The additional refinement of adding crossbars of differing heights for each season of the year is superfluous. USAGE OF THE SHADOW CLOCK

The small size of the surviving instruments and the dimensions which appear in the Osireion text describing the shadow clock suggest strongly that the instrument was intended to be portable. This is borne out by the provision of a hole for attaching a plumb bob cord in the gnomon block of Berlin Museum 19 , and also by the hieroglyphs in figure 5 which show plumb bobs suspended from the clocks and sundials. The manner of usage of a clock with a crossbar would require an accurate east-west alignment. A cardinal alignment is not a simple undertaking and certainly would not be produced by the clock instantaneously. Indeed, the crossbar clock would have to be aligned correctly in all three axes of rotation in order to achieve any consistency and accuracy in use. The crossbar clock is by nature a stationary instrument, and would have to be set up on a datum line and turned at noon, to be consulted in situ at any time. It would therefore need stability, which is not provided by the long crossbar placed on top of the existing gnomon block. The pattern of usage of the crossbar clock is inconsistent with the wellattested plumb bob attachment and the size of the surviving instruments. CONCLUSION

If the addition of the crossbar is discarded, the clock becomes a portable instrument that can be used at any location. Alignment is provided by levelling 19. Berlin Museum, 19743.

18

SARAH SYMONS

the instrument using the plumb bob and by pointing the device towards the sun20 . The correct alignment will be indicated by the shadow of the gnomon block falling exactly on the scale. This as described in the Osireion text passage in figure 3 "then the shadow of the sun will be aligned on this sf3t ". The simple ratios between the markings on the scale suggest a convenient " rule " for making a clock, rather than an accurate measure for seasonal hours. With no attachments but the plumb bob, the markings on the scale do not measure seasonal hours. Although seasonally-adjusted hours during the night were being measured by water-clocks during the New Kingdom, there is no evidence to confirm that the day hours and the night hours were perceived as being of the same nature. The shadow clock was possibly the only timekeeping instrument extant during the New Kingdom to have secular as well as sacred applications. It is possible that the time defined by the shadow clock was therefore used for different purposes to the time defined by star clocks and waterclocks. Standardisation of time was probably not the goal of all timekeeping devices. There was no concept of twenty-four continuous hours forming one day until Greco-Roman times. The time periods around dawn and sunset were clearly considered to be transitional periods and were not divided formally in New Kingdom times. The hypothesis of the crossbar is inconsistent with what is now known about Egyptian timekeeping. The evidence presented above suggests that shadow clocks were L-shaped, portable, sun-aligned devices for personal use. FIGURES

Plumb Bob

1. Parts of a shadow clock. The hypothetical crossbar is unshaded. 20. A detailed description of the method is given in : M. Isler, "The gnomon in Egyptian antiquity", JARCE, vol. 28 (1991), 155-185.

EGYPTIAN SHADOW CLOCKS

19

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2. Diagram heading the shadow clock text in the Osireion at Abydos.

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