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Compilation of the

Notarial Act.


Compiled by: Fred Kats.

Table of contents:

The Notarial Act (links to transcripts and translations).
Contract summary.
About Coster and Fromanteel.
Who promised to disclose a secret.
Daags dienvolgend'  versus  'Soo is dienvolgens.
The translation of 'volmaecken'.
About the Piggott paper.


Source document, P1. P2.
Chr. Huygens' Œuvres Complètes. (pdf)
Chr. Huygens Horologium 1658. (pdf) 26

The Piggott paper.
Speculations on the historical backgrounds of the contract.

"I am aware of the fact that we will never be absolutely certain about the incentives of the
visit by Coster and Fromanteel to Mr. de Putter's
(notarial) office."                           Frits van Kersen. 

"The historic Contract, between Salomon Coster and John Fromanteel, remains curious and by no means understood, but is only one of the many unresolved enigmas in the history of European horology."
                                                                    Keith Piggott.


It is commonly believed that Christiaan Huygens was the first to combine a pendulum with a verge clock in 1656. In June 1657 he had a pendulum clock most likely made by Salomon Coster and patented in the United Provinces (the Netherlands), and it was published in his 'Horologium' in 1658.

Fig. 1 (click for more)
Christian Huygens. 1629-1695

The improvement was so dramatic that other clockmakers followed suit. It is assumed that Huygens permitted Salomon Coster to provide training on pendulum clocks to foreign clockmakers, one of them was John Fromanteel son of Ahasuerus a London clockmaker of repute.

This compilation is about the Notarial Act (contract) between Coster and Fromanteel (Sept. 1657) which, as commonly understood, enabled Fromanteel to learn about Huygens' new and famous pendulum clocks.


Combined Facsimile and Transcript:

The van der Horst 'Working sheet' 28

Five Transcriptions:

The 'Vollgraff' transcription.5,3
The Dobson transcription 8
The van Lieshout transcription.
The van Kersen transcription.10
The van der Horst transcription 28
The Rob Memel transcription

Three Translations:

The Dobson translation.3,17
The van Kersen translation.10
The van Klaveren translation.29

Fig. 1a (click to enlarge)
Coster-Fromanteel contract
facsimile of the first page.
(view high resolution version)
© Municipal Archives, The Hague.

Fig. 1b (click to enlarge)
Coster-Fromanteel contract
facsimile of the second page.
(view high resolution version)
© Municipal Archives, The Hague.


John Fromanteel was:

to work for Salomon Coster from September 3rd 1657 until May 1st 1658.
to make clocks, as he did before, either in the shop or in the house of Coster’s.
already a capable clockmaker.


Salomon Coster was:

to pay 20 caroli guilders15. for each clock made by Fromanteel.
to pay 18-10-0 caroli guilders for each clock made by Fromanteel if Coster supplies the brass and steel.
to pay for Fromanteel's heat, light and beer during this period of time.
to disclose, before May 1st 1658, the secret 16 existing in the clocks made by Fromanteel, provided that the clocks made by Fromanteel will remain at Coster’s.


Salomon Coster,  ante 1623 - 1659.

Salomon was born in Haarlem in
the United Provinces (the Netherlands) before 1623 and moved to The Hague shortly after his marriage in 1643. Like several Haarlem clockmakers, he was a Baptist. In 1646 Pieter Visbagh was apprenticed to him for six years, and in 1657 Christiaan Reijnaert for ten years. In the same year Christiaan Huygens allowed him ('met privilege') to make and sell pendulum clocks. In this year John Fromanteel came from London and worked with Coster, followed by Nicolas Hanet from Paris in 1658. Salomon Coster died suddenly in December of 1659 and the following year the shop was taken over from Coster’s widow by Pieter Visbagh.
2   End

John Fromanteel, 1638 - ante 1692.

John was apprenticed to his father in 1652. Part of his apprenticeship was spent in the Hague with Salomon Coster where he was trained to make pendulum clocks. After he brought the new skills back to London in 1658, the Fromanteel family made the first English clocks, using a verge and a short pendulum. He became a Freeman of the Clockmakers’ Company in 1663. He took four apprentices between 1663 and 1679, one of whom was his son Ahasuerus III. He appears to have worked in the family business until about 1680 when he went to Holland with Ahasuerus II to pursue the family clock making business there and may well have died there before his father’s will was made in 1692.

Fig. 2 (click to enlarge)
Facsimile of Ahasuerus Fromanteel's advertisement in "Mercurius Politicus" October 1658.

End of this section, click here to continue.

Footnotes & Further reading.

1. Municipal Archives, The Hague, Notarial Archive.
Beheers №372, Inventaris №322, Folio 409 & 409 verso.

2. Dr. R. Plomp, Spring driven Dutch pendulum clocks 1657-1710. (Schiedam: Interbook International B.V., 1979)

3. R. D. Dobson. ‘Huygens. the Secret in the Coster-Fromanteel Contract, the Thirty-Hour C1ock, in: Antiquarian Horology. Vol. 12. No. 2. Summer 1980. P. 193-196. 

4. Hans van den Ende, Dr Frits van Kersen, Maria F. van Kersen-Halbertsma, Dr John C. Taylor and Neil R. Taylor, Huygens’ Legacy, catalogue of an exhibition held at Paleis Het Loo, (Castletown, Isle of Man: Fromanteel Ltd, 2004), 

5. Chr. Huygens, Œuvres Complètes de Christiaan Huygens, (The Hague: M. Nijhofl’, 1888-1950), Vol.17, pp.21-22.  
(go to

Chr. Huygens, Œuvres Complètes de Christiaan Huygens, (The Hague: M. Nijhofl’, 1888-1950), 2  no. 565.

6. E.L. Edwardes, the suspended Foliot and new Lights on early Pendulum Clocks’, Antiquarian Horology, 12/6, June, 1981.

7. E.L. Edwardes and R. D. Dobson, ‘The Fromanteels and the Pendulum Clock’, Antiquarian Horology, 14/3, September, 1983.

8. R. D. Dobson, † 2005. De slinger als tijdmeter. Een nieuwe visie op de ontwikkeling van de slinger als tijdmeter in de periode van 1602-1660. Galileo Galilei- Ahasuerus Fromanteel - Christiaan Huygens. Achterland Verlagscompagnie. Bocholt Bredevoort/Uitgeverij Fagus, Aalten. p.41.

9. E.L. Edwardes, The Story of the Pendulum (‘lock, (Altrincham, John Shcrrart & Son Ltd., 1977), p.58-59

10, Frits van Kersen, ‘The Coster-Fromanteel Contract Re-examined’, Antiquarian Horology,
28/5, March 2005, p.561-567.

11, B. Loomes, Complete British clocks, (Newton Abbot: 1978), pp.43ff.

12. E.G. Aghib and J.H. Leopold, ‘More About the Elusive Fromanteel’, Antiquarian Horology, 8/8, September
1974, 890ff.

13. According to J.H. Leopold Coster was a Baptist because he did not have his young children baptized, and because his widow did the administration of the small Baptist community in The Hague for many years (see: Municipal Archives The Hague, Archief Doopsgezinde Gemeente). For more on Coster see: J.H. Leopold, ‘Een Reishorloge door Salomon Coster’, Jaarverslag Kon. Oudheidkundig Genootschap, 119-123 (1976-1981), 72-76. for Fromanteel’s religion see note 12.14 

back to early pendulum clocks  


Back to previous section.  Go to section end



Fig. 3 (click to view full transcription)
Error in Vollgraff's transcription of the contract,
as discovered by B. van Lieshout .

It appeared that the printed transcription in Huygens
'Oeuvres Complètes' Vol XVII.5 contains an error. According to Leopold14 and van Kersen, correcting this error does not really change the meaning of the text.
However according to Piggott and van Lieshout it causes the meaning of the text to change significantly.

Piggott's paper reads: "..., the noted Dutch horologist Berry van Lieshout made the first forensic verbatim transcript of the famous 1657 Contract; including marginal notes, deletions and amendments. He found errors in former transcripts all scholars relied on,...... Berry and I long debated the significance of Coster's name being reinstated into the 'secret clause'; finally we both surmised it gave a new mirror-image of all previous understandings.

The 'common 17th c. Dutch' (Leopold/van Kersen?) and 'revised'  (Piggott/van Lieshout?) interpretations could possibly be distinguished as follows:

In Dutch: 
Wijders soo heeft hij Coster belooft hetzelve werck dat hij fromanteel sal maecken, (ende het secreet daerinne bestaende), hem voor den voorsz. geexpereerden tyt te openbaren mits...

common 17th c. Dutch understanding
: Wijders soo heeft hij Coster belooft [hij = Coster die belooft] hetzelve werck dat hij fromanteel [hij = Fromanteel] sal  maecken, (ende het secreet daerinne bestaende), hem [hem = Fromanteel] voor den voorsz. geexpereerden tyt te openbaren mits..

revised understanding
: .. wijders soo heeft hij Coster belooft [hij = Fromanteel die belooft] hetzelve werck dat hij fromanteel [hij = Fromanteel] sal  maecken, (ende het secreet daerinne bestaende), hem [hem = Coster] voor den voorsz. geexpereerden tyt te openbaren mits...


10: Further so has he Coster promised to reveal the same work that he Fromanteel will make (and the secret therein existing) to him before the aforementioned expired time, provided.....

common 17th c. Dutch understanding
: Further so has he Coster [he = Coster who promised] promised to reveal the same work that he Fromanteel [he = Fromanteel] will make (and the secret therein existing) to him [him = Fromanteel] before the aforementioned expired time, provided... 27

revised understanding
: .. further so has he Coster [he = Fromanteel who promised] promised to reveal the same work that he Fromanteel [he = Fromanteel] will make (and the secret therein existing) to him [him = Coster] before the aforementioned expired time, provided...


  'The following day...' versus   'So is subsequently...'
   ('Daags dienvolgend..' versus  'Soo Is dienvolgens..')

Most differences between the Van Kersen and the Van der Horst transcriptions do not really affect the meaning of the text. However there is a striking difference at the last line of page 1.

Fig. 4 (click to view source document)
'Daags dienvolgend..' versus 'Soo Is dienvolgens ...'

Van Kersen's 'The following day..' transcription, apparently leads him to his 'first day concept' and 'second day additional agreement' theory. Accordingly he concludes:

 10 "Obviously, as the first draft clearly reveals, it was on the following day that an additional agreement was written down, .."

 10 "The fact that the joint agreements on Coster's promise to reveal something and the clocks staying in Coster's workshop, apparently were made on a second day, after the primary conditions of Fromanteel's employment by Coster were recorded, suggests that the revelation of the secret was not the main object of the contract in its first day-concept."

However the Van Kersen theory is not endorsed by the Van der Horst's transcription which reads:  'Soo Is dienvolgens ...' (So is subsequently...) in stead of 'Daags dienvolgend...' (The following day...)

Salomon Coster

Soo heeft


Fig. 5
The first character in fig 4 being an 'S' seems to be consistent with other transcriptions as applied by both
 Van Kersen and Van der Horst.

The full, scored out, lines in Dutch are:
Van Kersen: 10 "Daags dienvolgend tusschen seij contrahenten noch wordt versproocken, dat"

Van der Horst: Soo is dienvolgens tusschen hen contrahenten noch verder versproocken, dat 30


Another striking difference appears when comparing the van Kersen and the van Klaveren translations of lines 13-18.

To perfect his watchwork' versus 'To finish his clock making work'.

Van Kersen
Source transcription:

'...te sullen voltrecken en volmaecken...'

'...he John Fromanteel obliges and commits himself to execute and perfect his watchwork, ...'

Van Klaveren:  
Source (v.d. Horst) transcription:

'...te sullen voltrecken ende
he John Fromanteel shall oblige and bind himself to perform and finish his clock making work ...

As it appears from three Dutch dictionary entries31, 'perfectioneren' or 'vervolmaken' (to perfect) is not likely to be the primary meaning of 'volmaecken' (volmaken).

Middelnederlandsch Woordenboek 1300-1500 
Vroegmiddelnederlands Woordenboek 1200-1300  WNT=
Woordenboek der Nederlandsche Taal 1500-1976


'The Coster Fromanteel Contract its continued place in modern scholarship'. ........... is the title of Keith Piggott's paper on the possible pre-1657 introduction of pendulum clocks in England.

Some quotes:
section end

"Enthusiasts can contribute to the history by private research. Any tyro might find gold, where experts too familiar with old wisdoms do not. Our absorbing arena of antiquarian horology needs new blood, we must inspire and challenge younger minds to accept our roles so the definitive story of the 1657 Contract may one day be written."

"Orthodox dogma regards any contractual 'secreet' (be it remontoire? pendulum? escapement? theoretical calculation? endless rope? OP-gear?) as being solely in Coster's gift ...."

Second perspective regards a fatal error in Dereham’s chronology, shown by the Royal Society’s minutes for 1662 (Birch’s history, 1756). The RS pendulum clock is lost, but the chosen excerpt is misleading and a canard... Personally, I hold the link made is also fallacious."

(click here to view his thought-provoking paper)


We are indebted to Forum antiquariaat Bas Hesselink & Drs. Koert van der Horst, Wim van Klaveren, Berry van Lieshout, Keith Piggott, Drs. Ester Lels, Drs. Karel Nicolas, Hans Kreft, Achterland Verlagscompagnie, Dr. Frits van Kersen, The UK National Maritime Museum, The UK Science museum,  Scheepvaartmuseum Amsterdam and The municipal archives of the Hague and Rotterdam for their contributions, consent or services.

The Horological Foundation.  22-10-2005.
Project editor: Fred Kats.

This compilation is subject to ongoing revisions.


Footnotes & Further reading. (cont.)

14. J.H. Leopold, 'Some more notes on the Coster-Fromanteel contract', Antiquarian Horology, 28/5, March 2005, 568-570. 

15. 1 Caroli Guilder = 20 sols = 1 Flemish pound (lb) = 1.8 guilder.

16. In spite of various speculations, it most likely is to unfold the secret engineering aspects on how to construct pendulum clockworks. Editor's note.
(more speculations on the secret)

17, Hans Kreft. Rediscovering the Fromanteel story. Translated and adapted for the Horological Foundation website by R.K.Piggott. (go to

18 ‘The Fromanteels and the Pendulum Clock’, Antiquarian Horology. (June 1984), 632-633.

19 Dr. R. Plomp. The Dutch extraction of the Fromanteel family. Antiquarian Horology, sept. 1971.
p 320-372.

20 R.D. Dobson, ‘The Development of the Pendulum Clock. 1656-1659’, in: Antiquarian Horology, Vol. 13, No. 3, March 1982, P. 270-281.

21 E.L. Edwardes and R.D. Dobson. ‘The Fromanteels and the Pendulum Clock’, in: Antiquarian Horology, Vol. 14, No. 3, Sept. 1983, p. 250-265.

22 R.D. Dobson, ‘Galileo Galilei and Christiaan Huygens’, in: Antiquarian Horology. Vol. 15, No. 3, March l985,p. 261-270.

Dr. R. Plomp. The Dutch origin of the French pendulum clock. What we can learn from Christiaan Huygens' correspondence. 1657-1664. Antiquarian Horology, sept. 1971. p 24-40.

Dr. R. Plomp. The Dutch influences in French clockmaking and visa-versa in the latter half of the seventeenth century. Antiquarian Horology, dec. 1974. p 28-45.

Keith Piggott. The Coster Fromanteel contract, its continued place in modern scholarship. A paper on the possible pre-1657 introduction of pendulum clocks in England. THF website Sept. 2005. (go to)

26 English translation by Ernest L. Edwardes in Antiquarian Horology Volume 7, No. 1, December 1970.

Van der Horst: 'he Coster' is in my view 'he (=Coster)', as in the 'common interpretation'. Also with respect to the preceding and following text.

28 Drs. Koert van der Horst (1944), curator of manuscripts at the University Library Utrecht (retired). Now head of bibliographical research and catalogue department with Antiquariaat FORUM, ‘t Goy-Houten, the Netherlands.

29 W. A. van Klaveren, graduated at Rotterdam Polytechnic in 1971 as a mechanical engineer, acquired an MA in English language and literature at the Free University of Amsterdam (1979), became a lecturer at Leiden University, the Free University and Delft University respectively, and at various teaching training colleges specialising in Old and Middle English Language and Literature (1979-1984); worked for the European Commission, first as a translator, later as a language coordinator. Got involved in antique clocks in 1985 and was trained as a restorer in the workshop of Mario Crijns. 'Wim' was the editor of the recently published 'Clocks - Their origin and development, 1320-1880' by H.M. Vehmeyer.

30 Drs Ester Lels' advice to consider the 'Soo is dienvolgens' transcription caused the initiative to ask Antiquariaat Forum for their professional 'van der Horst' transcription of the entire manuscript. The Horological Foundation is indebted to both experts for their indispensable contributions.

31 Volmaken, (vol = full  maken = to make).

32 Rob Memel together with Victor Kersing started an archive research on Salomon Coster. Their goal is to map the story of Coster and his family.

volmaken, voltooien, afmaken, ten einde brengen. Voc. Cop. volmaken, efficere; volmaken, peragere. Plant. volmaken, achever de faire, accomplir, perficere, fastigium imponere operi, opus aliquod imponere, absolvere; vide volbringen. Kil. volmaecken, perficere, absolvere, expolire, extremam manum imponere.
voltooien; volmaakt maken; realiseren; in zijn geheel beslaan?
voltooien, ten einde brengen; den uiteindelijken vorm geven.
Tot (een hoogeren graad van) volmaaktheid brengen; beter, perfecter maken; perfectioneeren.
MNW= Middelnederlandsch Woordenboek 1300-1500 
Vroegmiddelnederlands Woordenboek 1200-1300  WNT=
Woordenboek der Nederlandsche Taal 1500-1976
Source: De geïntegreerde taalbank

Further reading:

Early Pendulum Clocks.

back to text.