Clock types · Novelty and art clocks

Mystery clock

A clock whose hands seem to turn on a clear glass dial with nothing driving them, an illusion perfected by a French magician and later by Cartier.

By David Ray · clocks.fyi

What a mystery clock is

A mystery clock hides how it works. The hands sit on a transparent dial of glass or rock crystal, and there is no visible spindle, wheel or wire linking them to any movement. To the viewer they seem to drift around the dial on their own.

The term covers a few different designs, but they share the same goal: to make an ordinary timekeeping job look impossible. The most famous examples come from two sources, the Paris clockmaker and stage magician Jean-Eugene Robert-Houdin in the nineteenth century and the jeweler Cartier in the twentieth.

How the illusion works

The movement is real and ordinary; it is simply hidden. In a Robert-Houdin mystery clock of about 1850 described in the online catalog Museum Collection (mus-col.com), the clockwork sits in the base, with an eight-day power reserve, a lever escapement and a half-hour strike on a bell. Its motion travels up a rotating inner glass tube inside a glass column and, through a worm gear, turns a glass disc that carries the single hand.

Cartier's clocks use a similar idea in a different shape. According to Phillips, the auction house, the hour and minute hands are each fixed to a separate crystal disc with teeth around its edge, and those teeth mesh with the hidden movement. Sotheby's describes the same arrangement, with gears concealed in the side or central supports and linked to a movement in the base. Because the teeth sit inside the metal frame, nothing connecting the hands to the movement can be seen.

Secrecy was part of the appeal. The Paris auction house Piasa reports that Louis Cartier would not let his clockmakers explain the mechanism even to the firm's own salesmen.

See also: an ordinary analog face with nothing up its sleeve on OnlineClock.app.

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Robert-Houdin's mystery clocks

Jean-Eugene Robert-Houdin (1805 to 1871) became famous as an illusionist, but he was also a working clockmaker in Paris. The Morris Museum in New Jersey, which showed mystery clocks from the collection of Richard Garriott in 2024, says his mystery clocks debuted at the 1839 Exhibition of French Industry, where their hands seemed to move with no connection to any mechanism.

He made his clocks in series and kept refining them. The Morris Museum dates a second-series example to about 1838, and a third-series clock in the Museum Collection catalog is dated to about 1850, so the type stayed in his hands for well over a decade. Exact dates for each series are not firmly settled.

The third-series clock in that catalog, from about 1850, stands 53.5 cm tall, with a transparent glass dial on top of a glass column rising from a wooden base covered in blue velvet and decorated with cast openwork mounts. The dial is signed Robert Houdin Paris, and the movement plate carries the stamp Houdin.

Cartier and Maurice Couet

In the early twentieth century Louis Cartier set out to revive the effect. He worked with the clockmaker Maurice Couet, who drew on Robert-Houdin's ideas, according to the Museo Nacional Thyssen-Bornemisza in Madrid. In 1912 Couet produced the first Cartier mystery clock, named Model A. Phillips reports that it was sold to the banker John Pierpont Morgan, and Piasa says the name was a playful nod to Ford's Model T.

Sotheby's describes the original Model A as a rock crystal case on a white agate base, with floating hands inside concentric rings of gold and diamonds, and notes that the model went on being made for decades in different versions. Couet refined the design in 1920 with a central axle, driven through a single point of connection, which gave Cartier more freedom with shapes and decoration.

In 1923 the movement was housed in the top of a Portique clock, which the Thyssen describes as an unprecedented technical feat. Phillips counts six Portique clocks in all, completed between 1923 and 1925.

Sources differ on some details. The Thyssen calls Couet Cartier's exclusive supplier of table clocks, while Piasa describes him as a young independent watchmaker who had worked for the Prevost workshop, then Cartier's supplier. Piasa says mystery clocks were made regularly rather than only to special order, but Sotheby's says almost all of the elaborate two-pillar models were unique commissions. Piasa also reports that production stopped during World War II and returned in the early 1980s.

How to recognize one

The clue is a clear dial with hands but no visible center post or gearing behind it. Look through the dial: on a mystery clock you see the room behind it, not a movement.

Next, find where the clockwork has gone. On Robert-Houdin's clocks it sits in the base, with winding and hand-setting holes at the back. On Cartier's pieces it is concealed in the frame or base around the crystal.

Not every clock with a glass dial is a mystery clock. If you can see a central arbor passing through the glass to a movement behind, the clock is simply skeletonized or glazed, not hiding its drive.

Be careful with related Cartier pieces. Sotheby's notes that the prism clocks Cartier introduced in 1937, designed by Gaston Cusin, are not strictly mystery clocks, even though they share the same air of hidden workings.

See also: other clock styles, from banjo to bracket on OnlineClock.app.

Questions people ask

How do the hands on a mystery clock move?

Each hand is fixed to a transparent glass or crystal disc. Hidden gears in the base or frame turn the edge of that disc, so the hand moves without any visible connection to the movement.

Who invented the mystery clock?

The French clockmaker and magician Jean-Eugene Robert-Houdin is credited with the early mystery clocks, which debuted at the 1839 Exhibition of French Industry in Paris. Cartier's version, by Maurice Couet, followed in 1912.

What was Cartier's Model A?

The first Cartier mystery clock, made by Maurice Couet in 1912. Sotheby's describes it as a rock crystal case on a white agate base, and Phillips reports that it was sold to J. Pierpont Morgan.

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