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The earliest DUTCH and FRENCH
Pendulum clocks, 1657-1662.


About R. Plomp

Table of contents:

Historical data.
A comparison of very early
pendulum clocks
, (view comparison matrix).
Seven characteristic properties of early clocks.
Special features of individual clocks.

Chr. Huygens' îuvres ComplŔtes. (pdf)
Chr. Huygens Horologium 1658. (pdf) 26

About  R. Plomp.

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On 26 December 1657 Christiaan Huygens (1629-1695) writes to the French astronomer Ismael Boulliau (1605-1694) that he had made his first pendulum clock "yesterday just a year ago", and that since June he had been showing the construction to everybody interested

This last remark is related to the fact that on 16 June 1657 Salomon Coster (c. 1620-1659) had obtained the exclusive rights ('privilege') for a period of 21 years to make and sell these clocks.

The earliest description by Huygens.
The earliest description by Huygens is in his letter to Jean Chapelain (1594-1674) in Paris, dated 28 March 1658.

A drawing explains the principle in Huygens'
letter to Chapelain. (click to enlarge)

Christiaan Huygens


Jean Chapelain

A drawing explains the principle; in Huygens' own clock the balance wheel is replaced by a six inch long pendulum suspended from a thread. It seems likely that Huygens is referring here to the timepiece made by Salomon Coster with a pendulum of 13.7 cm, of which five have been preserved. Shortly afterwards, Huygens tries to get his pendulum clock also granted in France. As he fails, he hastens to publish his new invention in "Horologium" (September 1658). In concluding the text, Huygens gives some information on the clocks as designed by Coster:

"I have indeed seen in the workshop of him whose labours I first employed for these constructions completed pendulum clocks which go not by a weight but by the force of a spring. In this kind of work, up to the present time, the differing power of the spring when wound up and when run down was equalised by the aid of a fusee round which was coiled a gut line; now these are disused. For the teeth are brought together with the barrel itself, in which the spring is enclosed. Although it is admitted that by this method the motion of a pendulum is not equally vigorous in the beginning and at the end [of the spring power], nevertheless the effect is not to reduce the time of the concluding oscillations, as has been proved earlier. The manner of adjusting and apportioning the spring-tension, in fact is such that no slight loss in timekeeping occurs during the working of the timepiece. I pass over clocks of this kind which have been contrived to sound the hours by one and the same motor, either a weight or a spring, which serves also for turning the hands of the timepiece, since all these have no connection with my invention."

We learn from this translation of Huygens' exposition that the movements by Salomon Coster did not have a fusee and that the production was not restricted to timepieces; Coster made also clocks with an addition striking train driven by the same spring.

Huygens' letter to Pierre Petit, November 1658.
A letter by Huygens to Pierre Petit (1598-1677), dated 1 November 1658, informs us more closely about his two measures to further the accuracy of the clock. In order to eliminate the effect of the pendulum's amplitude as much as possible, Huygens introduced curved cheeks which diminish automatically the length of the pendulum for larger amplitudes. The optimal shape of these cheeks he determined experimentally. Shortly after this date (at least prior to 22 January 1660) he deduces mathematically that the ideal cheeks should have the shape of a cycloid, () and for that reason we refer to them as cycloidal cheeks. As a second measure for spring-driven clocks, Huygens indicates that the variations of the spring can be reduced by limiting the number of revolutions of the spring barrel.

This letter presents still more information on Coster's clocks. Winding the spring directly has the advantage of the going train being permanently under tension, so that the clock will not stop during this operation. Coster provides his domestic clocks with a minute ring around the hour ring. He needs only one extra wheel to show the phases of the moon, the days of the month and of the week. The clocks have a horizontal escape wheel, in this respect deviating from the construction given by Huygens in 'Horologium', where he introduced an additional gear to minimise the amplitude of the pendulum not provided with curved cheeks. Coster just informed him that he needed three to four weeks to make a spring-driven clock with striking, price D. fl. 120. The clockmaker made such clocks going for a week on a single spring.

Coster clocks pricelist, January 1659.
In a letter by Huygens to Boulliau  dated 16 January 1659  we find a specification of the various clocks deliverable by Coster, including prices:

Coster clocks, price list in guilders, Jan. 1659
Weight Spring Striking 30 hr. 8 day Price
Huygens' letter to Boulliau.

Ismael Boulliau, astronomer

A Coster clock described in Florence, 1690.
A very important additional source of information on Coster's clocks is an inventory made up in Florence in 1690. It gives the description of a hanging clock with a short pendulum in an ebony case with a glass front, half an ell high, with a silver chapter ring on velvet and an ornament, also silver, inscribed 'Salomon Coster'. This clock was sent to the grandduke Fernando II de' Medici (1610-1670) on 25 September 1657 and indicated as the first pendulum clock arrived in Italy.
This historical survey gives a surprisingly detailed specification of the earliest pendulum clocks made by Salomon Coster: a movement with or without striking, driven by the same barrel, provided with a horizontal escape wheel, with the pendulum suspended on a thread between (more or less cycloidally shaped) cheeks, length about six inches, the dial plate covered with velvet on which a single chapter ring for the hours as well as the minutes and a dito silver cartouche with the name of the maker, all this as a hanging clock in an ebony box with a glass front. It sounds like the des-scription of the clocks which have survived the three and a half centuries since their construction.

Two foreign co-workers.
Salomon Coster could make use of the labour of two foreign co-workers in the few years prior to his early death in December 1659. The more wellknown was John Fromanteel (1638 - prior to 1692), son of Ahasuerus Fromanteel (1607-1693), clockmaker in London. How the news of the new invention reached him is not known. Possibly through John Roussel, born in The Hague in 1633 as the elder son of the clockmaker Cornelius Roussel, originating from London. From 1655 to 1657, this John was apprenticed to a London clockmaker. Both Johns came to The Hague in 1657, both are mentioned as witnesses in a certificate dated 13 October 1657.

John Fromanteel.
On 3 September 1657 Salomon Coster and John Fromanteel signed a deed according to which the latter agreed to make clock movements in Coster's shop as he had already done before. For each movement he will receive D.fl. 20.- if he uses his own brass and iron, D. fl. 18.50 if these materials are provided by Coster. The fixed unit price indicates that Fromanteel was to make a series of identical movements; it seems evident that the agreement refers to the most simple version of a spring-driven timepiece, price D.fl. 80.-. As John Fromanteel is mentioned in deeds dated February 1659 and October 1660, we may assume that he was working again in The Hague in those years. It is possible that he kept Coster's workshop going after the latter's sudden death in December 1659 until it was taken over by Pieter Visbagh (c. 1634-1722) in November 1660.

Nicolas Hanet.
A second temporary co-worker, also from abroad, is the Paris clockmaker Nicolas Hanet (?-1723). The fact that he is referred to in Huygens' correspondence as 'Sieur Hanet' gives the impression that he was more than just an average artisan. We find Hanet for the first time mentioned anonymously as 'Coster's agent' who worked with him in The Hague, in a letter dated 29 November 1658. It is tempting to suppose that Hanet's interest had been roused through contacts with the Paris correspondents of Huygens.

From the correspondence we can conclude that Nicolas Hanet visited The Hague at least three times: in September 1658 he returns from his first visit to The Hague, during which he may have worked with Coster, with two or three Coster clocks. These first pendulum clocks in Paris were bought by Louis Charles d'Albert, Duc de Luynes (1620-1690), mentioned as a 'grand amateur' of clocks. We hear also that Hanet himself made a pendulum clock in 1658. The second journey to The Hague takes place in February-March 1659, in which case Hanet returns to Paris with four Coster clocks. In December 1659 he travels for the third time to The Hague, apparently for a short visit. As a result of the sudden death of Coster his return is delayed to March/April 1660. This may indicate that Hanet worked in the preceding months in Coster's shop, possibly finishing clocks designed for Paris clients. In a certificate of 23 December 1659 Claude Pascal authorises Nicolas Hanet to collect 41 pounds in his name. From the correspondence we can conclude that in 1658-1660 at least eleven clocks by Salomon Coster have been brought to Paris, partly by Hanet, partly sent with books of the Leiden publisher Elsevier. Thanks to the letters preserved we are rather well informed about the transactions to Paris, but unfortunately we have no data on clocks made for Dutch clients.

Considering the number of clocks mentioned and the cooperation of John Fromanteel, Nicolas Hanet, as well as the orphan Christiaan Reijnaert (c. 1647-1699), who as a ten year old orphan was apprenticed to Coster in 1657, we may assume that in less than three years Coster's shop had a large output of pendulum clocks. On the basis of his statement that he needed 3 to 4 weeks to make a clock, it seems reasonable to suppose that in the years 1657-1660 at least 30 to 40 clocks were delivered in and outside the country.

Thanks to the fact that Huygens' involvement with the 'export' of pendulum clocks was continued for some years after Coster's death, data on the further development have been preserved. His visit to Paris (October 1660 to March 1661) discloses that in the mean time three or four clockmakers in that city are producing pendulum clocks; (Gilles) Martinot (1622-1688) is menČtioned by name as having been visited by Huygens twice. We can assume that, in addition to MarČtinot and Nicolas Hanet, Isaac Thuret (c. 1630-1706) belonged to this group.
Back in The Hague, Huygens receives new requests for clocks to be delivered under his supervision. In a letter from January 1662 Claude Pascal is mentioned for the first time. We know of him only that he originated from France or Geneva, worked in The Hague at least since September 1654 and died shortly after 1670. Apparently in the beginning Huygens was very satisfied with his work, for in the time up to 1664 he employs him six or more times for making clocks ordered from Paris. For five of these clocks Christiaan Huygens himself is a witness of the state in which they arrive. In two cases he criticises the quality of the clocks as being made not as well as his earlier clocks. The other three have suffered so seriously during transport that he calls on Isaac Thuret, whom he may have met through his contacts with the Paris astronomers, to repair the clocks. From the letters of Christiaan Huygens to his brother Constantijn in The Hague we learn that some of these were striking clocks and that the case of one clock was veneered with tortoise shell.

In view of these bad experiences, Huygens decides in April 1664 not to charge himself any more with ordering clocks. Without doubt, this decision was also due to the fact that, as his father Constantijn had already reported during the latter's visit to Louis XIV in 1661, the Paris clockmakers were making better pendulum clocks than their confreres in The Hague, clocks he prefers to his own 'Hague' clock. Christiaan Huygens asks for a description of how the clocks by Thuret are designed but, unfortunately, this description is not preserved. We may assume that his father's preference concerned primarily the more beautiful finish of the French clocks compared with the sober design of the Coster clocks.


We have seen above that Huygens' correspondence, his 'Horologium' and the Florence inventory present us with a surprisingly good picture of the first pendulum clocks made by Salomon Coster. For the earliest communication of preserved clocks we have to thank to J. Drummond Robertson who discovered two samples in the Rijksmuseum in Amsterdam in 1923. In his book 'The Evolution of Clockwork' (1931) he gives an extensive description of a small clock with a silver chapter ring, only an hour hand and the backplate signed 'SAMUEL COSTER - HAGHE met privilege', with the additional note that this clock has since disappeared. He depicts the second clock, described as larger and more elaborate; this is the clock now in Museum Boerhaave in Leiden.

Seven Coster clocks rediscovered.
At this moment, seven clocks by Salomon Coster have been rediscovered, whereas from Claude Pascal at least 18 clocks are known. These numbers are large enough for a special study of Coster clocks and very early Dutch and French clocks most similar to them. This restriction aims at the very sober box-shaped clocks with a minimum of ornaments, the prototypes of the clocks we now know as 'Haagse klokken' and 'pendules religieuses'. In total 19 Dutch and 6 French clocks were found which satisfy the criterion. Of the Dutch clocks seven are by Salomon Coster, ten by Claude Pascal, one by Severijn Oosterwijck and one by Pieter Visbagh; the French clocks are by various makers.

These 25 clocks represent the earliest phase of the pendulum clock, a phase which has - as could be expected - a strongly experimental character. By trial and error Coster and his direct followers were developing a clock type well justified in terms of their construction and satisfying the aesthetic taste of potential buyers. The prices between D.fl. 80 and 130 may seem low in our eyes, 350 years ago they represented considerable amounts. Studying the similarities and differences among the clocks can show the 'degrees of freedom' available in the early development, converging in the more or less established design of the later 'Haagse klokken' and 'pendules religieuses'.

Objects can be compared effectively by tracing the typical characteristics, or features, in which they are similar and in which they are dissimilar. We may expect that the more features two objects have in common, the more their origins are related.

The objects, in our case the clocks, can be collected in a matrix in which the rows represent the clocks and the columns represent the characteristics involved. In this matrix, the clocks are ordered in such a way that for row 2 the clock is selected with the largest number of features common with the clock of row 1, subsequently for row 3 the clock left with the largest number of features common with the clock of row 2, etc. This approach was applied successfully in dating a large number of 'Haagse klokken' in 'Spring-driven Dutch Pendulum Clocks 1657-1710' (1979).

  A limited number of characteristics compared.
A conditio sine qua non of this procedure is that the objects to be compared have a limited number of characteristics in common. Features they all share do not contribute, whereas features only found in a very few objects are of no use either. In the comparison table presented below only features shared by at least three clocks were accepted. This criterion resulted in seven characteristics which were ordered as columns according to their frequency: three referring to the movement, three to the case and one to the attachment of the chapter ring. The restriction to seven is a choice; originally more features were examined, but the ultimate selection was determined by considering their relevance to the process of the clock's development. This approach is not free of subjectivity; it should be judged by the extent to which the result is convincing. It should be clear that features shared by less than three clocks, even features that are unique, are not unimportant. On the contrary; they will be discussed in the next section.

The procedure was carried out as follows. The point of departure is Coster clocks with a large number of common features: D1-D3. The fact that D1 and D2 are clocks with the date 1657 on their cartouches justifies the assumption that they represent the earliest version of the pendulum clock made by Salomon Coster in the first year of the patent (they happen to be also the first Coster clocks discovered). D3 shares all seven features with D1 and D2, D4 shares six, D5 shares three, etc. Similarly the columns are ordered from high to low number of common characteristics. In the matrix the presence of a striking train is indicated in a separate column, but this feature has been left out of consideration.

Fig. 2 (click to enlarge)
A comparison matrix of 25 early clocks.


The seven characteristic properties applied in the matrix are the following.

Windows. (in the side panels of the case)
A striking feature of the earliest pendulum clocks is the absence of windows in the left and right side panels of the case. The fact that six out of seven Coster clocks have no windows, whereas only two of the other clocks are without, confirms the absence of windows as an early characteristic. Strikingly, all six French clocks share this feature and agree in this respect most with the Coster clocks.

Door frame.
The next column also concerns the case: five clocks by Coster have plain (flat) door frames against two other Dutch clocks and two French clocks; three of the other clocks have moulded frames, eight have frames veneered with tortoise shell and three have repoussÚ brass ornaments (in the two cases left, the original execution of the frames is unknown).

Aperture (in back plate)
This is the first property of the movement. The backplates of all five Coster timepieces (D1-D5) have a rectangular aperture to accommodate the escape wheel. Only two clocks by Pascal share this aperture against four French clocks.

Pillars. (shape)
The square pillars between the plates of the movements of these five clocks are traditionally considered characteristic for Coster. The clocks with striking D8 and D10 show that Coster himself also applied baluster pillars, almost exclusively seen in later clocks.

In order to accommodate the steady pins of the escape wheel's upper cock, the backplates of four Coster movements have two small holes near the upper edge. This appears to be a typically early Coster feature, not seen in any other clock.

Key (to unlock the front door).
The front door of these four clocks are locked with a special key, whereas the other three Coster clocks as well as the other Dutch clocks use the winding key. With only one exception, the French clockmakers followed Coster's earliest solution, which became standard in later French clocks.

Chapter ring  (fastening)  SectionEnd
A quite remarkable property of only three Coster clocks, probably never noticed before, is the use of rivets to attach the chapter ring. The disadvantage of this construction, which made it very difficult to replace the velvet covering the dial plate, is obvious. Coster abandoned the rivets very soon, providing his other chapter rings with feet, which were pinned behind the dial plate, universally applied in later clocks. A modified version is seen in the French clocks F1 and F2, with screws rather than rivets. This solution was frequently used by Isaac Thuret in his clocks with wooden dial plates.

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 (click to enlarge)
The key feature of this article is a
comparison matrix considering seven characteristic properties of 25 early clocks.


After the more general investigation of features shared by at least three clocks of Salomon Coster, it is relevant to look for additional features of the individual clocks.

D1, Salomon Coster.
(click for more)

D1 Timepiece; cartouche signed 'Salomon Coster Haghe met privilege 1657'. Special features: iron dial plate; door hinges attached to the outer side of the case. Reference 1, 114-115; reference 2, 24-27 (Museum Boerhaave, Leiden).

D2, Salomon Coster.

D2 Timepiece; cartouche signed 'Salomon Coster Haghe met privilege 1657'. Special features: fixed dial plate; case with back door. Reference 1, 116-117; reference 3, vol. I, 282-283 (Vehmeyer collection).

D3, Salomon Coster
(click for more)

D3b, Salomon Coster
(click to enlarge)

D3 Timepiece; cartouche signed 'Salomon Coster Haghe met privilege 1657' (replacement). Special features: barrel cap attached to the barrel with a 'dovetail' construction; transmission wheel between minute and hour hands, at the front not supported with a special cock but with an enlarged cock of the hour wheel; hinges of the dial plate combined with the hinges of the door. Reference 1, 118 (Museum van het Nederlandse Uurwerk, Zaanse Schans)

D4 Timepiece; cartouche signed 'Salomon Coster Haghe met privilege'. Special features: none. Reference 1, 119 (Science Museum, London).

D5 Timepiece; cartouche signed 'Salomon Coster Haghe met privilege 1658'. Special features: movement originally gilt; ratchet at the back of the movement; separate alarm train, with the bell on top of the case; dial plate turning on pins (private collection).

D5, Claude Pascal.

D6 Timepiece; cartouche signed 'Claude Pascal HagŠ HollandiŠ'. Special features: no minute hand; backplate signed 'C. Pascal'; ratchet at the back of the movement. Reference 3, vol. I, 286-287 (Vehmeyer collection).

D7 Timepiece; cartouche signed 'Claude Pascal Fecit HagŠ'. Special features: no minute hand; ratchet at the back of the movement; dial plate covered with red tortoiseshell; very small case. Reference 1, 188 (private collection).

D8, Salomon Coster.

D8 Clock with striking; cartouche signed 'Salomon Coster Haghe Met privilege'. Special features: movement originally gilt; bell inside the case. Reference 1, 120; reference 2, 32-33 (Museum van het Nederlandse Uurwerk, Zaanse Schans).

D9, Severijn Oosterwijck.

D9 Clock with striking; cartouche signed 'Severijn Oosterwijck Fecit Haghe Met privilege'. Special features: bell inside the case; dial plate turning on pins. Reference 2, 34-35 (private collection).

D10, Salomon Coster.

D10 Clock with striking; cartouche signed 'Salomon Coster Haghe Met Privilege'. Special feature: bell inside the case. Reference 3, vol. I, 226-227 (private collection).

D11, Claude Pascal.

D11 Clock with striking; cartouche signed 'Claude Pascal La Haye'. Special features: backplate signed 'Claude Pascal La Haye'; bell inside the case; probably early in France, the original case has been furnished with extra base and top as a pendule religieuse. Reference 1, 184-185; reference 2, 30-31 (private collection).

D12 Timepiece; cartouche signed 'Claude Pascal A La Haye'. Special features: backplate signed 'C. Pascal'; ratchet at the back of the movement. Reference 1, 182-183 (Museum Boerhaave, Leiden)

(click to enlarge)
D13, Claude Pascal.

D13 Timepiece; cartouche signed 'Claude Pascal HagŠ HollandiŠ'. Special features: ratchet at the back of the movement. Reference 3, vol. I, 284-285 (Vehmeyer collection).

D14 Clock with striking; cartouche signed: 'Claude Pascal Haghe Hollandiae'. Special features: backplate signed 'C. Pascal'; bell inside case; unusually small movement (private collection).

D15 Clock with striking; cartouche signed 'Claude Pascal HagŠ HollandiŠ'. Special features: bell inside the case; probably early in France, the original case has been furnished with extra base, top and brass ornaments as a pendule religieuse. Reference 1, 186 (private collection).

(click to enlarge)
D16, Claude Pascal.

D16 Timepiece; cartouche signed 'Claude Pascal HagŠ HollandiŠ'. Special features: ratchet at the back side of the movement; cast and gilt upper spandrels; gilt repoussÚ lower spandrels, cartouche and ornaments on the door frame. Reference 1, 187; reference 3, vol. I, 288-289 (Vehmeyer collection).

D17 Clock with striking; cartouche signed 'C. Pascal HagŠ HollandiŠ'. Special features: second barrel for grande sonnerie; backplate signed 'C. Pascal'; gilt repoussÚ cartouche and ornaments on the door. Reference 1, 191 (private collection).

D18 Clock with striking; cartouche signed: 'Pieter Visbach Fecit HagŠ Met privilege'. Special features: bell inside the case. Reference 1, 220 (Guildhall, London).

D19, Claude Pascal.

D19 Clock with striking; cartouche signed: 'Claude Pascal HagŠ HollandiŠ'. Special features: backplate signed 'C. Pascal'; bell inside the case; hour hand directly driven; gilt repoussÚ cartouche and ornaments on the door. Reference 2, 36-37 (private collection).

F1 Clock with striking; cartouche signed 'G Martinot Aux Galleries'. Special features: backplate signed 'G Martinot Aux Galleries'; fixed dial plate; bell on top of the ebonized case; gilt ornament on top of the door; minute wheel at the front not supported with a special cock but turning on a shaft fixed to the front plate. Reference 1, 42 (private collection).

F2, Pierre Saude

F2 Timepiece; cartouche signed 'P. Saude AParis'. Special features: no minute hand; iron dial plate; backplate signed 'Saude AParis'. Reference 1, 39; reference 2, 40-41 (private collection).

F3 Timepiece; cartouche signed 'Jacques Hory AParis'. Special features: ebonized case. Reference 1, 41 (private collection).

F4, F. Gilbert.

F4 Timepiece; cartouche signed 'F Gilbert Angers'. Special features: five-minute division on chapter ring; backplate signed 'F Gilbert Angers'; case veneered with walnut. Reference 1, 40; reference 2, 42-43 (private collection).

F5, Nicolas Hanet.

F5 Clock with striking; cartouche signed 'Nicolas Hanet AParis'. Special features: dial plate turning on pins; bell on top of the case. Reference 3, vol. II, 790-791 (Vehmeyer collection).

F6, Jean Hubert.

F6 Clock with striking; cartouche signed 'Jean Hubert ARoŘen'. Special features: bell on top of the case, case veneered with red tortoiseshell and walnut. Reference 3, vol. II, 798-799 (Vehmeyer collection)


From the general comparison presented by the matrix table, together with the special features of the individual clocks, the following conclusions can be drawn.
Roughly considered, the matrix reveals a division into three categories: (1) most clocks by Coster, (2) the clocks by Pascal, Oosterwijck and Visbagh, and (3) the French clocks. Of course, there are no sharp dividing-lines; the three groups overlap each other. Rather than representing three phases in time, they indicate that Coster's clocks served as models both for his successors in The Hague as well as their confrŔres in France. The finding that the few early French clocks appear to be more similar to the clocks by Coster than most clocks by Pascal does not necessarily point to more conservatism of the Paris clockmakers. We should realize that, as Huygens' correspondence indicated, they left the simple 'box' behind earlier than the Hague clockmakers did.

Looking more in detail, we should mention in the first place that the plates of the movements of the five timepieces by Coster are of equal size (109-110 mm x 58-59 mm), whereas the plates of the five timepieces by Pascal are all different. This agrees surprisingly well with the contract between Salomon Coster and John Fromanteel. As this contract referred to a fixed 'tariff', we may consider the equal sizes as confirming that Fromanteel was hired for the production of a series of timepieces, of which a few samples fortunately have been preserved. Additional support is the fact that the square pillars of these movements, never used in other Dutch and French clocks, are also seen in early clocks from the workshop of Ahasuerus Fromanteel in London.

A closer comparison of the five movements D1 to D5 yields still more typical similarities. As was already mentioned, they are the only clocks with an aperture in the backplate for the escape wheel, very rare in later clocks. Moreover, the form and/or finish of the cocks holding the verge are not only mutually similar, but also more representative for the English rather than the Dutch tradition, with the exception of D3. The movement of this clock is provided with a cock more in line with other early clocks made in The Hague. As we have already seen in the previous section, the design of the spring barrel, too, deviates from the other Coster timepieces. According to L.H.J. van Lieshout, this construction had been applied by Salomon Coster before in his table clocks. His suggestion that the movement of D3 was made by Coster himself (or under his direct supervision) sounds acceptable.

Another remarkable variation concerns the transmission between minute and hour hands. In D3 Coster applied a rather 'primitive' solution by providing the enlarged cock of the hour wheel with an aperture around the pinion of the minute wheel to fix its position (see the picture on p. 118 of reference 1). In clock D10 Coster used a stud fixed in the front plate for the minute wheel; this is the usual English construction. In all other cases, followed by Pascal and the later Hague and French clockmakers (with F1 as an exception) a special cock is used to support the minute wheel and pinion. These different constructions demonstrate Coster's search for the best solution to the challenge of providing a clock with two hands.

Whereas the Pascal clocks beginning with D12 in the matrix have none of the seven characteristics of D1 and D2, there is a transition range in which clocks by Coster and Pascal are difficult to distinguish on the basis of their features. This similarity may point to a (short) period prior to Coster's death during which Pascal made and sold pendulum clocks under his own name. On closer examination, there is further evidence supporting this supposition. In 'Horologium' Huygens refers to Coster as "him whose labours I first employed for these constructions'', as if other clockmakers, too, have been involved in his clock experiments. More significant seems to be the striking fact that Pascal signed all of his clocks with which I am familiar with the indication of the place name 'Den Haag' as 'la Haye' or 'Hagae' sometimes with the addition of 'Hollandiae', whereas he never adds 'met privilege' used by Oosterwijck and Visbagh in a few cases. This may indicate that, as Huygens tried in vain to get a French patent for his invention, Pascal was free in 1658 and 1659 to make pendulum clocks to be exported to France and other countries. The contact between Pascal and Hanet confirms this view, as well as the fact that so many Pascal clocks have been found in France.

Notwithstanding the fact that the clocks signed by Coster represent only a period of less than three years, a clear progress is still visible. Not only in view of their dating may we consider D1 and D2 as his earliest clocks, with D3 directly connected. Their most striking common feature is the application of rivets for the attachment of the chapter ring. Evidently, this construction is so inappropriate that it is very unlikely to have been applied after the feet were introduced, seen in all other Dutch clocks. In some other aspects the first three clocks differ, demonstrating the experimental phase: the iron dial plate and the visible hinges of D1, the fixed dial plate of D2, and the combined hinges for dial plate and door of D3, three unique constructions in 'Haagse klokken'. This early 'freedom' holds also for the dial plates turning on pins of Coster's D5 and Oosterwijck's D9, frequently seen in French, but never in later Dutch clocks.

Most clocks by Claude Pascal have features common with 'later' clocks by Salomon Coster, with one exception: the repoussÚ ornaments of D16, D17 and D19. Most likely, these ornaments were Pascal's answer to the news from Paris about the much more beautiful clocks made in that city. The ornaments on the door frames as well as on the top of the cases have a rather isolated position in the Dutch development, whereas they link quite well with similar, but cast ornaments in early Paris clocks by Isaac Thuret and other makers.
Lastly, it is very interesting to read from the matrix table that the prototype clocks by Salomon Coster rather than the clocks by Pascal were the models for the French clockmakers. One of the most striking similarities between clocks D1-D4 and the French clocks is the use of a special key for locking the front door. Already Coster himself preferred to use the winding key in his other clocks, universally followed by the other Hague clockmakers. The horizontal aperture for the key in D1-D4 suggests that Coster applied simple locks designed for drawers, adapted by the French makers. The screwed chapter rings of the clocks F1 and F2, followed for some years by Thuret with his wooden dial plates, present further evidence that Coster's earliest clocks should be considered to be the models for the first French pendulum clock.  END

I wish to thank W.A. van Klaveren for his willingness to read and improve the text.

Reinier Plomp.   Dec. 9, 2005.



References: Footnotes & Further reading.

1. R. Plomp, Spring-driven Dutch Pendulum Clocks 1657-1710. Interbook International, Schiedam, 1979. This book gives the references to Huygens' correspondence and other sources mentioned in the text. (buy this book)
About  R. Plomp.

2. H. van den Ende, F. van Kersen, M. F. van Kersen-Halbertsma, J. C. Taylor, and N. R. Taylor, Huygens' Legacy. The Golden Age of the Pendulum Clock. Fromanteel Ltd, Castletown, Isle of Man, 2004.
(buy this catalogue)

3. H. M. Vehmeyer, Clocks - Their Origin and Development, 1320-1880. Snoeck publishers,
Gent, 2004.  (more on this book, buy this book)



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