Search this article. Use 'Enter' key to find next.  Use 'Home' key to search again.

Speculations on the historical
backgrounds of the

notarial act.








Table of contents:

Opinions & Speculations floating Table. (ost)

Compilation of the Coster-Fromanteel notarial Act.
Source document, P1. P2.
Chr. Huygens' Œuvres Complètes. (pdf)
Chr. Huygens Horologium 1658. (pdf) 26

Note: Yellow characters indicate bookmarks or 'clickable' links to relevant pages or bookmarks.

"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.

"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. 


It is commonly believed that Christiaan Huygens whas 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. Huygens permitted Salomon Coster to provide training on pendulum clocks to foreign clockmakers. John Fromanteel, son of Ahasuerus, a London clockmaker was one of them. 

This page is about the Notarial Act (contract) between Coster and Fromanteel (Sept. 1657) which enabled Fromanteel to learn about the new and famous pendulum clocks.

Or was it John Fromanteel as a sub-contractor, who's father already (?) made his own less successful version of the pendulum clock, who was to disclose a secret to Coster (and Huygens) ?

Neither do we know whether or not the contract was satisfactory fulfilled by both parties or informally abandoned before the end of the term ?

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. (back to text)

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

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

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),  (back to text)

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

5a Chr. Huygens, Œuvres Complètes de Christiaan Huygens, (The Hague: M. Nijhofl’, 1888-1950), 2  no. 565.
back to text)

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

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

R. D. Dobson. 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. (back to text)

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

10, Frits van Kersen, ‘The Coster-Fromanteel Contract Re-examined’, Antiquarian Horology,
28/5, March 2005, p.561-7.
(back to text)

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

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

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 text)

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

15. 1 Caroli Guilder = 20 sols = 1 Flemish pound (lb) = 1.8 guilder. (back to text)
16. In spite of various speculations, it most likely is to unfold the secret engineering aspects on how to construct pendulum clockworks. See also 'ost'. Editor's note.
back to text)

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

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

Dr. R. Plomp. The Dutch extraction of the Fromanteel family. Antiquarian Horology, sept. 1971.
p 320-372. (back to text)

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

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. (back to text)

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

Dr. R. Plomp. The Dutch origin of the French pendulum clock. What we can learn from Christiaan Huygens' correspondence. 1657-1664. Antiquarian Horology, dec. 1972. p 24-40. (back to text)

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. (back to text)

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) (back to text)

English translation by Ernest L. Edwardes in Antiquarian Horology Volume 7, No. 1, December 1970.  (back to text)

Paper by A.J.(Alan) Emmerson, Jan. 2005: Things are seldom what they seem. Christiaan Huygens the Pendulum and the Cycloid. (go to MS Word doc.)
p 12: ..."So we are left with the simple fact that some time before 16 June 1657 Huygens, Coster and van Call produced a working pendulum controlled clock. We do not really know what it looked like. Distribution of credit between Huygens and Coster remains unresolved. These events, though, suggest that Coster may have contributed substantially to the design of the working pendulum clock. While this first Coster clock just may have had chops, they would not have been cycloidal, other than by coincidence".
(back to text)

28 Comment by Alan Emmerson, March 24 2006.
back to text)

back to text.



  Back to previous section.


It is interesting to observe the many opinions and speculations in articles, private deliberations and meetings on this subject.

The table below is to organize their various aspects and to rank (yes it's rather risky and arbitrary!) their possible likeliness.

Hopefully this table provides a low treshold for all those willing to contribute with even more opinions/speculations or comments. The Horological Foundation will gladly update the 'floating content' of this table with any brief and relevant contributions from readers.



Tip: table
Point your mouse to a character, number or bullet to get it explained,
or click it for more.

    B L P U
1 Coster and Fromanteel had socially much in common. 9    
2 We may assume that John had command of the Dutch language, which might explain why this contract is in Dutch. 19 10    
3 There was no condition for Fromanteel to acknowledge Huygens as inventor of the pendulum clock/system.      
4 Fromanteel already made some pendulum clocks before entering Coster's workshop. Line 18 of the contract: ..'like he Fromanteel  already has made some'. 13    
5 Fromanteel, already being a capable maker, required not much training attention.      
6 There was no fee, due to Huygens for each clock sold by Coster,      
7 There was an 'unofficial fee', due to Huygens for each clock sold by Coster. 3    
8 Fromanteel was a sub-contractor rather than being Coster's employee, and there was no condition for him to make a minimum number of movements before the end of the term.      
9 The cases and dials did not cost more than the movements.      
10 Fromanteel was to make complete (?) movements for 20 caroli guilders, Coster sold the clocks for 80 (?)  caroli guilders24.       14  
11 The contract does not mention any fees or restrictions for Fromanteel to make or market pendulum clocks in England.      
12 Considering the fixed price as agreed with Coster, Fromanteel was to make only one type of movements. 6    
As there is a fixed price agreed but no reference to a construction specification for Fromanteel to comply with, he on beforehand and as a test, was to make some samples under Coster's direction to rank as a 'product construction reference', ( he Fromanteel has already made some..).      
About the secret:
13 A secret was to be disclosed by Fromanteel in stead of by Coster. 25 12  
14 Although being apparent and effective in the movements made by Fromanteel, the secret's mathematical aspects were not readily detectable. 1
15 The secret was in the verge being horizontal, i.e. perpendicular to the movement plates. 11
16 The secret was in the one tooth/pin driven stopwork on the barrel, or the double train barrel, or an endless rope arrangement 8, or amplitude restriction constructions, or any other readily detectable aspects.  1
17 The secret was in the engineering aspects on how to construct the pendulum arrangement, i.e. pendulum length calculations and the (not yet cycliodal) cheek or chop curve features for a given pendulum length. 10 1
Although Huygens had experimented with curved plates (cheek or chop curves) in 1657 and 1658  () he was unable to determine the correct shape and he appears to have temporarily abandoned the idea in favour of the pirouette mechanism depicted in Horologium. It was not until December 1659 that Huygens analytically determined that the plates should be cycloidal. Thus at the time of the contract there was no "secret" to be revealed about the shape of the plates. 28  17    
18 Coster provided a 'cheek or chop curve template' for Fromanteel to make the curved plates, thus avoiding premature revelation of the secret mathematical aspects of the curve. 1
19 Fromanteel was to make incomplete movements for 20 caroli guilders, Coster was to finish the incomplete movements, which then were to be kept out of Fromanteel's sight. 14 1
    B L P U




  likely (L)      
  perhaps (P)      
  unlikely (U)      
  perhaps likely    
  perhaps unlikely    

back to table.


 Table footnotes. 

Possible Backgrounds: (B)   back to table

b1. The secret was in the work that he Fromanteel will make "(and the secret therein existing)"  (back to table)

b2. Fromanteel could mail a sketches and specifications to his father in London.
  (back to table)

b3. History is more than its appearance in official documents!?
  (back to table)

b4. Separate mounting of the pendulum suspension (with cheeks), independent from the verge cock.

(see example)  (back to table)

b5. There is no secret in a verge escapement, as it occurs already in earlier clocks and watches.
(back to table)

b6. Presumably the 30 hour spring driven time piece version.   Or the weight driven 30 hours (48 guilders) version? (back to table)

b7. Hard to keep it secret till the end of the period if you are to make these parts already during the period.
(back to table)

b8. Similar stopwork arrangements occured already in renaissance watches and earlier square table clocks by Coster. Not a significant secret (?) (back to table)

b9. For they were both Baptists (Mennists) and shared the same profession,13  (back to table)

b10.  We learned that John's father Ahasuerus was bi-lingual in English and Dutch 14  (back to table)

b11. A verge being perpendicular to the movement plates, was common practice in Renaissance watches and horizontal table clocks.
Huygens' oldest sketch of his pendulum arrangement shows the balance of, a horizontal table clock put in a vertical position.
 (back to table)

b12. 'No' according to van der Horst, 'Yes' according to Piggott/van Lieshout. More (back to table)

b13 According to van Kersen this means no more than that Fromanteel had made some clocks in Coster's workshop before Sept. 3rd. (back to table)

b14 A commercial opportunity. (back to table)

b15  The secret  was not to be revealed before the end of the contract period.
(back to table)

b16 Indispensable for future independent manufacturing of pendulum clocks by Fromanteel. (back to table)

b17 It is not sure whether or not other than 'cycloidal' chop curves could rank as a 'secret' for Huygens at this early stage of development (Sept. 1657). The curved chops (cheeks) appeared already on the clocks made by Coster at the time of the contract, hence their current curves were assumed to be part of the 'know how' exchanged between Coster and Fromanteel.
(back to table)

back to text.