By Kenneth Cobb

Mystery Clock by Jean Eugène Robert-Houdin

A glass and ormolu Mystery Clock was sent to West Dean dissembled from an international source to be reassembled. A simple enough request, however, the 1850s mechanical mystique of smooth running remained a challenge throughout the three-month process.

Jean Eugene Robert-Houdin, born into a family of watchmakers in Blois, France, was primarily a conjurer and practical joker and this clock is no exception as it is Robert-Houdin's "Fourth Series" of Mystery Clocks representing his continued improvement of mysterious timepieces that was in part driven by his rivals. The clock would have been pride of place, lit either by natural or candle light, whereupon its onlookers would have wondered at the science of telling the time without the hands being attached to conventional clockwork.

The movement and drive work were cleaned without using invasive techniques. One of West Dean's key strengths is that conservation departments work together on interdisciplinary projects; thus the glass was cleaned by students in the ceramics department and advice on cleaning the ormolu (using a specific mild detergent and deionised water) was supplied by the metals department.

Glass disc and dial in a special carrier prior to cleaning by ceramics students. The Indian ink marking on glass was fragile.

Cleaning ormolu figures in mild detergent and deionised water

Typical of the conservation approach is Robert-Houdin's signature in copper plate writing on one of the movement's brass plates being left with the patina as received since it is stable.

Signature on one of the movement's plates

The glass dial is supported by a gilded cast brass besel that splits into two. The two halves arrived without any fixings so new screws were made, six of which could fit onto a single match head & even these turned out to be too long.

New grub screws to hold the dial's besel together

One of the glass tubes was cracked beyond repair so a new one was made and fitted. Fitting entailed removing cast brass bosses from both ends and re-gluing to a new tube, ensuring the tube was vertical to support the dial and keys within the two bosses were aligned with each other otherwise, the dial would not face forwards squarely. Alignment during the gluing stage was aided through the use of a precision lathe.

Alignment of brass bosses to ends of new glass tube during glue curing process. Bored out boxwood chucks are used to achieve precise centering.

The movement itself was a challenge as previous repairs had probably exacerbated its primary weaknesses: the plates are long, with a minimum number of pillars to support the tensions of twin sprung barrels, thereby making the movement unstable.

Whenever you hide a mechanism, you render its repair more difficult. In this Mystery Clock the rotating lead off work, or connecting rods, wheels and a screw between the movement in the bottom and dial at the top, were hidden within the body of the object. There were so many interconnected links that it was not clear which connection or link was at fault. It was a question that took weeks to resolve.

Movement as received. Note the long brass plates with pillars at either end.

Movement after cleaning in white spirit. Hammer on far side of plates is used to strike a gong in the bottom of the black wooden base.

Two intermeshed links within the lead-off work that transmitted power between the movement and dial. This one was a ... difficult.

Finally, the clock ran reliably and sadly had to be returned as it was a considerable source of interest. For a student the clock has been a privilege to work on, having been a great source of learning, and patience, and with the tutorship of Matthew Read and Malcolm Archer I have gained a lot more understanding and confidence in this field. Thanks also to Lori Covington, an arts student, for editing the report.

One mystery remains: Did anyone ever use this clock to catch a train or plane successfully, as the complex lead-off work was designed not to be too tight, which meant the minute hand could be up to five minutes adrift either way?

My next clock is French too ...