Oddly Powered Clocks

Gallery opened: Oct 2004

Updated: 28 July 2022

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This gallery of the museum is dedicated to clocks with unusual motive power.
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Left: Drebbel's barometric clock: 1610

Cornelius Drebbel- the same remarkable man who is supposed to have rowed a boat underwater up the Thames- built in 1610 a clock telling the time, date, and moon phases. It appears to have been powered by changes in air pressure.

The clock mechanism is contained in the golden casing A in the centre. Around this is a circular tube containing water that is clearly at different levels on each side. The top of the tube appears to have connected to a piston or bellows inside the gold casing which wound a spring.

The mode of operation is somewhat speculative, but some very interesting experiments have been done by H R SantaColoma.

Left: Portrait of Cornelius Drebbel: ca 1631

Looking as though he has just emerged from the pub.

"Alcmarensis" means "coming from or originating in Alcmar". The modern spelling is not Alcmar, but Alkmaar. Thanks to Jonathan Fowler for providing this info.


Left: Cox's barometric clock: 1760s

In the 1760s the well-known clockmaker James Cox developed a clock which was were wound up by changes in barometric pressure. The work was done in collaboration John Joseph Merlin, with whom Cox also worked on developing automata. Two large glass vessels containing no less than 68 kilograms (150 pounds) of mercury worked as a massive barometer; they were connected together by an ingenious system of cords and pulleys so that the pulleys would rotate back and forth as the atmospheric pressure and so the glass vessels, rose and fell. A rack-and-pinion mechanism converted this to unidirectional motion so that winding of the mainspring occurred on both rising and falling pressures, and there was a safety-device to prevent overwinding. Cox claimed that his design was a true perpetual motion machine, which of course it was not.

The clock is shown here without mercury in the vessels. This is probably a safety-measure rather than an economy measure; if my calculations are correct filling the clock to get it working again would cost something like £600.

Cox was a well-known clockmaker. He showed his self-winding clock in a private museum along with other fine clocks. When he died in 1788, a Mr Thomas Weeks bought the clock for his museum. It stayed in his museum until his death in 1833. It was not included in the sale catalogue of his effects in 1834, and remained lost until 1898 when it was exhibited at the Clerkenwell Institute. After a period on loan to the Laing Gallery in Newcastle, it was auctioned, and finally acquired by the V & A Museum in 1961.

Cox's clock has a Wikipedia page, but it does not give much information.

Left: Cox's barometric clock: 1760s

A contemporary engraving of Cox's clock, where it is described as 'A Prize in the Museum Lottery'. Presumably this refers to Cox's private museum rather than that run by Mr Thomas Weeks, as the engraving is dated to 1774. It is not normal for museums to raffle off their exhibits; possibly Cox had despaired of selling it for an adequate sum. Note the confident claim of perpetual motion.

In this view, the driving weights either side of the glass vessels can be seen.

From the engraving, it appears the clock originally had an ornamental urn perched on top, which now seems to be missing; I assert it looks better without it.

Cox's clock is still in the Victoria & Albert Museum in London, but I do not know if it is on display; one of these days I mean to go and find out.

You can see more of Cox's work on the V & A Museum website.

A biographical review of James Cox has been written by Clare Le Corbeiller.


You might think that a hydrogen-powered clock would function by using the gas to run a small internal-combustion engine that would rewind a spring or raise a weight, but a little thought shows that this would be a complicated (and noisy) bit of machinery. Pasquale Andervalt had other ideas...

Left: The hydrogen clock of Pasquale Andervalt: 1835

The hydrogen clock was made by Pasquale Andervalt in Italy in about 1835. There seems to be some evidence that several were built, but this is the only survivor. Very possibly all the others blew up.

The red glass jar contained sulphuric acid. Zinc pellets were stored in the brass spiral above the clock. When a pellet was dropped into the acid, hydrogen was evolved and this pushed up a small piston that raised the driving weight. The clock has a pin-pallet escapement, and the ornate pendulum can be seen in front of the red jar.

The big wheel above the dial has the driving cord running over it, and this wheel was pushed upwards by the piston and cylinder below it, raising the driving weight at bottom left. The smaller weight near the top of the red cylinder at the right simply kept the driving cord taut.

The hydrogen was then presumably released to the atmosphere when a port in the cylinder was uncovered. The clock dropped a pellet automatically when it was running down, and given the large number of pellets that could be stored in the brass spiral, it would presumably run unattended for a very long time. Eventually it would of course be necessary to replenish the pellets and replace the exhausted acid. I imagine the Unique Selling Proposition was something like "almost perpetual motion".

Thus the inflammable nature of hydrogen was not exploited at all. It all seems a bit hazardous- you have a big glass jar of sulphuric acid, and clouds of hydrogen wafting about. If the pellet-dropping mechanism malfunctioned, and dropped all the pellets into the acid at once, there would seem to be a good chance that the clock would explode, sending glass fragments in all directions; followed by a second explosion when the released hydrogen encountered the nearest naked light. One hopes there was some sort of safety-valve.

Carbon dioxide might have been safer as a working fluid- marble pellets could have been dropped into hydrochloric acid. However, in the event of a multi-pellet incident, there might be issues with suffocation. The ideal gas would appear to be nitrogen, but I am not aware of any way to generate it by dropping a solid into a liquid. The standard laboratory method of preparing nitrogen is to heat a mixture of ammonium chloride and sodium nitrite dissolved in water; this evolves ammonium nitrite which is unstable and breaks up into nitrogen and water. Laboratory textbooks warn you to avoid explosions when doing this. (Though they are less clear on how to avoid them) The process does not sound too practical for a clock.

Author's photograph

On further thought, what about oxygen as a working fluid? That should be safe enough, unless the concentration in the air becomes high enough to make ordinary materials highly flammable; that seems highly unlikely. So, can we make it by dropping pellets of something into a liquid? One method that suggests itself is dropping pellets of sodium peroxide into ordinary water. This will react "violently or explosively" evolving oxygen and caustic soda, so better make the pellets fairly small. Actually sodium peroxide reacts violently with all sorts of things, and I'm not sure we are heading in the direction of greater safety.
Oxygen can be evolved by dropping manganese dioxide into 6% hydrogen peroxide, but this is a catalytic decomposition and I imagine all of the hydrogen peroxide might decompose at once, bringing back the possibility of an explosion.

Other gases which can be made by dropping solids into liquids are chlorine and sulphur dioxide, but I think the drawbacks there are obvious.

At this point I ran out of innocuous gases, and appealed for anyone with more chemical knowledge than me to suggest a working fluid for this clock that would neither blow you up nor poison you. I received this reply from my correspondent Pigeon:

"In response to your request for comments on possible alternative working fluids:

As a non-serious suggestion: acetylene, from calcium carbide dropped into water. The exhaust is not vented, but stored in a reservoir, and used to feed a little flame so you can still see what time it is at night. (I am presuming that the working pressure does not exceed 1 bar gauge, of course.)

Being serious, though, I would definitely plump for carbon dioxide: unreactive, non-toxic and dead easy to make.

As a suffocation hazard it can be ignored. It is only dangerous in that regard if there is so much of it that it displaces enough oxygen-containing air that you can't profitably breathe the result, which would require a heck of a lot of it. The amount of substance contained in the clock's curly reservoir tube could not possibly produce that much CO2 unless both you and the clock were trapped in a compartment so small that you'd soon breathe all the oxygen in it anyway.

As far as suffocation hazards are concerned, nitrogen is actually worse. Both act purely by displacing breathable air, but CO2 will provide at least some warning that this has happened, because the body determines how hard it needs to breathe principally by detecting excess of CO2, not shortage of oxygen. So excess of CO2 in the atmosphere will cause breathlessness and clue you in that something is wrong (although in practice the effect is small and it still helps to be on the alert for it).

Nitrogen, on the other hand, as one might expect since we breathe 78% of it all the time, produces no warning at all; you just fall over. There was an incident in the King's Cross area when the Victoria line of the Underground was being constructed, due to ingress into the works of air that had percolated down through the clay, losing its oxygen on the way to reactions with reducing minerals and ending up as more or less pure nitrogen. As long as construction was actually in progress there was enough ventilation that this didn't matter, but when operations were paused for the weekend and ventilation ceased, the tunnels filled up with nitrogen. Result was that the first blokes through the door on Monday morning just plain conked out more or less instantly. Fortunately someone following on was sufficiently with it to realise what had happened, so they were able to rescue them in time and without the rescuers suffering the same fate.

And of course CO2 can be produced by the reaction of chemicals so commonplace and harmless that they can be obtained from standard kitchen stock. Vinegar and bicarb will do it. Or vinegar and chalk, for something that conveniently comes as lumps rather than powder.

(Just make sure it's real chalk: blackboard chalk doesn't work, because it isn't chalk, it's gypsum - calcium sulphate. This was a source of disappointment to me at school, when I pinched blackboard chalk out of the classroom and put it into the vinegar pot at dinner, expecting lots of CO2 and a frothy squirty mess... only to find that nothing happened at all. Which continued to puzzle me right up until the internet came along and told me what blackboard chalk really was)"

At this stage I questioned. I pointed out that there certainly is such a thing as carbon dioxide poisoning, also known as hypercapnia, though a 10% concentration is likely to be needed to kill. However 7% brings on mental confusion. Pigeon replied:

"...Assuming for the sake of argument that a Total Pellet Release Incident generates 100 litres of CO2, to achieve a 10% concentration would require that both you and the clock were shut in a cabinet so small as to leave only 1 cubic metre of unoccupied volume, which would not be a situation you'd willingly get yourself into in the first place. To generate 100 litres of CO2 at STP requires about 400g of calcium carbonate; guesstimating from your photo I'd reckon the capacity of the coiled tube, in terms of pellets of chalk, is of that order, so I still think we're safe."

I am convinced. Carbon dioxide it is.

The clock is currently on display in the Science Museum, London. The clock was presented to the Museum of the Worshipful Company of Clockmakers by William Wing in 1874. The only William Wing known to Google was an entomologist who died in 1855, so the donor is currently mysterious.

Left: The hydrogen clock of Pasquale Andervalt

This picture is an improvement on the one here before. It shows at bottom centre, just beyond the end of the pipe, the critical valve that drops zinc pellets into the acid. (Unfortunately it is hard to get sharp pictures through glass) There is a round port into the jar, closed with a disc which is presumably pressed up against its seating when there is pressure in the jar.

Further back up the pipe there is some sort of geared mechanism for releasing pellets one at a time, but its details are not clear. This mechanism is triggered by the lever (seen just above the spoked wheel) when the carriage holding the big wheel descends.

The spoked wheel is one of the four guiding wheels for the up and down movement of the carriage.

Author's photograph


Left: The Beverly Clock: 1864

The Beverly Clock is displayed in the foyer of the Department of Physics at the University of Otago, Dunedin, New Zealand. It is powered by changes in barometric pressure, and more importantly temperature, acting on a 1 cubic-foot box of air which presses on a diaphragm and raises the clock weights, presumably by some sort of ratchet mechanism. A temperature variation of 3.3 degC over a day gives enough power to raise a one-pound weight by one inch.

The clock was built by Arthur Beverly in 1864. The clock has, like the Atmos described below, a torsional pendulum with a very slow period that requires very little power to keep it working; torsional pendulums are used in so-called "400-day" clocks. The Beverly Clock occasionally stops if the ambient temperature has not fluctuated enough.


Left: The ether-powered clock of M. Henri Bernardi: 1875

This clock is powered on the same principle as the drinking bird. The arrangement of bulbs and pipes contains ether, and since the word is not qualified it is presumably diethyl-ether, which boils in the bulbs immersed in water. The bulbs are covered with a fabric net, and are cooled by evaporation when exposed to the air. This condenses the ether in the bulbs, unbalancing the wheel and causing it to rotate.

The obvious snag here is that diethyl-ether (CH3CH2–O–CH2CH3) does not boil at normal room temperatures; it boils at 34 degC at standard atmospheric pressure. Dimethyl-ether (CH3–O–CH3) boils at -23 degC so apparently that won't work either. However, the drinking bird normally uses methylene chloride which boils at 40degC. The answer to this conundrum seems to be that the pressure in the bulbs is below atmospheric, so the boiling point is reduced; it can be adjusted to be very near normal ambient temperature by controlling the amount of pressure reduction. Methylene chloride is safer than diethyl-ether because it is neither flammable nor explosive in air; however it is a neurotoxin and very probably carcinogenic, so I'd stay away from it.

The La Nature article claimed that a clock on this principle had been running for two months in the laboratory of M. Bernardi, without renewal of the water. The machine has about it a distinct air of Perpetual motion but it is of course no such thing. It is driven by the temperature difference between the bulbs in the water trough and the evaporation-cooled bulbs in the air, working as a Carnot Engine. The temperature difference is very small so the efficency is very low, though I'm not sure how the efficiency would be defined. I don't feel that gets to the ultimate source of the power, and I would be glad to hear any opinions on the subject.

There is a similar unsatisfactory situation with the Crooke's Radiometer. I have one of these and it undoubtedly works, but how it works has been much debated.

Bernardi has a Wikipedia page, but it does not mention his ether motor.

From article in La Nature 1875, p80

This is translated from the La Nature article:

According to the laws of the mechanical theory of heat, mechanical work can be produced by the use of any difference of heat. The solution of the problem of the production of work, obtained according to this principle, was sought in the following way by an Italian physicist, M. Henri Bernardi:"

"Two similar glass flasks are connected by a thin tube, also made of glass. The ends of this tube pass through the flasks with a rectangular bend. One of these flasks contains a small tube which makes it possible to introduce ether into the apparatus. The ether is brought to boiling, and when all the air has been expelled, the tube is closed using a torch. * The quantity of ether contained in the system must be such that it fills three quarters of a flask. In the middle of the connecting tube there is a part through which passes a metal axis, on which the whole system can turn. When the ether is equally shared between the two flasks, the device is in an unstable equilibrium. The axle supports sit on top of a rectangular box, which has a slot through which the rotary system passes."

"The crate is full of water, into which the flasks plunge alternately in this rotational movement. Each flask is covered with a very fine trellis. It is easy to understand that this device adopts a circular motion."

"Due to the unstable equilibrium of the system, one of the flasks, which we will call A, descends carrying all of the ether, while the rest of the space is filled with vapour. The flask A is thus in the water, and the other flask, which we will call B, in the air. The thin layer of water spread over B begins to evaporate, which cools the container and consequently condenses the vapour. The ether thus condenses in B, until finally B contains more ether than A, and plunges in its turn, A rising again. And so on. This circular movement only stops when there is no more water in the box to moisten the surface of the lowered flask."

"It would be difficult to mechanically take advantage of this thermo-engine. Also, Mr. Bernardi has modified his device in the following way: the two flasks or balloons described above are connected by a tube whose ends are bent (at right angles) in opposite directions. Three similar systems form a kind of wheel, and the centers of the six balloons are with the tube in the same plane. This wheel is supported on an axle, which presses against the lid of a rectangular box, in such a way that, in its rotation, it always has one half submerged and another emerged."

"The balloons are covered with a trellis and the crate contains just enough water for a single balloon to be completely immersed in it. Starting the engine by one turn of the wheel, a continuous rotation is obtained, and through a suitable set of pulleys the wheel can lift a weight or do other work."

"A similar thermo-motive wheel has been running a clock in M. Bernardi's laboratory for two months. The balloons are 0.78 inches in diameter, the center to center distance is 3.1 inches, and the amount of ether in each system fills three quarters of a balloon. The clock that this wheel keeps moving is shown above. The water level, by a special arrangement, is maintained at the same height. Mr. Bernardi was able to operate his wheel for three months, without renewing the water or cleaning the balloons. He calculated the quantity of heat displaced by this device and taken from the surrounding environment: it is equivalent, in 24 hours, to 60 wheel movements or revolutions, which are worth half the work consumed in the same time by the clock. **"

* "The ether is brought to boiling, and when all the air has been expelled, the tube is closed using a torch."

I would have though that would be very hard to do without blowing up both the apparatus and yourself. It also gives no hint as to how a carefully controlled pressure below atmospheric could be established in the tubes.

** "He calculated the quantity of heat displaced by this device and taken from the surrounding environment: it is equivalent, in 24 hours, to 60 wheel movements or revolutions, which are worth half the work consumed in the same time by the clock."

This statement is puzzling, for it seems to say the thermal engine only generates half of the power required to run the clock.

Two vital facts are missing from the above account: how much torque does the motor deliver and how fast does it go round? Drinking birds have in my experience a cycle time measured in minutes as water evaporates slowly.


Left: The French Alcohol Clock: 1902

This clock was powered by the thermal expansion of alcohol, responding to changes in the ambient temperature. The alcohol was contained in the two columns on each side, which were made of copper, presumably to speed thermal transfer. The details are not yet translated, but the expansion of the alcohol was amplified by the two curved levers, which wound up the clock via steel ribbons. Ethanol has a volumetric expansion coefficient of 0.00109 per degC, about five times that than water at 0.000214 per degC. Somewhat better again is ether at 0.00160 per degC, but we're trying to make a clock, not a time-bomb.

Ether seems to be the most expansive of the common liquids, unless you count Dichlorodifluoromethane refrigerant (R-12) which has 0.0026 per degC. However its manufacture is banned as it plays havoc with the ozone layer.

The caption says: "Clock that rewinds itself automatically with alcohol"

Many thanks to my correspondent Roland for drawing this machine to my attention.

Source: La Nature 1902, Trentième année, premier semestre: n°1489 à 1514

On another page, I explore the possibilities of using the thermal expansion of solid rods to wind up a clock; I think it is entirely practical, if possibly cumbersome.


Left: The French Water Pressure Clock: 1914

According to Popular Mechanics for April 1914: (p552) "The variations of pressure in the water mains are utilised by a French inventor for the operation of a self-winding clock." And that's all they wrote.

Presumably there was a spring-loaded piston, or equivalent, that moved as the water pressure varied with the daily demand cycle; that should provide plenty of power to wind up a clock. Whether it would work with modern water supplies, which one imagines would have good pressure regulation, is another matter. I have not been able to find any data on water pressure variations. Can anyone help?

In Paris this invention would have had to face severe competition from the pneumatic clock network, which distributed time over a large area.

Google has nothing on this.


Left: Cornu's Thermal Clock: 1920

(1) The heat from the burner vaporises the liquid in bulb B and the pressure drives the liquid into bulb A, causing the arm to tilt. (2) At the same time a cover is moved over the burner so B is no longer heated. It cools, reducing its internal pressure, and counterweight P returns the arm to its initial position. The see-saw action of the arm winds up the clock through a ratchet R.

This does not impress; it is hardly convenient or economic to keep a lamp burning continually just to wind up a clock. Furthermore, the heat is completely wasted for half of the cycle. This idea appears to have got nowhere and I can't say I'm surprised.


Left: The Junghans Electronome: 1927

The Junghans Electronome clock was powered electro-pneumatically; the glass bulb in the background contained a heating element which caused the air in the bulb to expand. The increased pressure passed through a rubber hose to moved a piston in the brass cylinder in the foreground, which wound up a conventional clockspring. The bulb was switched on and off once a minute by cam-operated contacts.

Junghans acquired the patents for pneumatic clocks, dated 1927, from the inventor, Martin Fischer of Zurich. The clocks were distributed in Germany by Junghans under the name "Elektronome"

The four gears on top of the clock are what is usually called the motion work. It is a 12-1 reduction gear train that drives the hour hand from the minute hand. It is joined to the going train of the clock by friction coupling from the cannon pinion, so both hands can be turned by hand to set the time. It is usually outside the front plate of the clock, and beneath the dial.

Left: The Junghans Electronome: 1927

The 'kolben' (piston) has a helical spring under it to return it when the air cools.

The pressure generated was sufficent to operate up to six slave clocks with their own drive cylinders. The minute contacts could be used to switch another six electrical slave clocks.

No dropper resistor or suppression capacitor is shown.

Left: The Junghans Electronome: 1927

This shows the clock in its vertical operating position. The power comes in at top left. At top right is a dropper resistor, which looks to be adjustable for differing mains voltages. On the right is the compressor lamp. The round thing at the bottom is a multi-way adapter for the compressed air; it is not connected here.

Left: The Junghans Electronome: 1927

The air-heating bulb.

Left: The Junghans Electronome: 1927

This shows a striking version of the clock with four different hammers and chime rods. The 'luftepumpe' (it is not a pump) is the cylinder with the piston moved by the expanding air. The kondensor (capacitor) was presumably connected across the contacts to prevent radio interference.

Note the 'J' for Junghans on the air-heating bulb.


Left: The back of a Puja clock made by the German firm of Jauch and Schmid: 1940

The notion here is to power a clock reliably when faced with mains electricity of uncertain voltage and frequency. It is perhaps significant that the patent for the principle (No. 714,893) was granted in Germany in 1940. It would work from either AC or DC mains. In Britain AC and DC coexisted for some time; I am not sure if that was the case in Germany; but judging by the advert below it was, and the mains could be either 110V or 220V.

At the lower left, shielded by a translucent housing, is a carbon rod resistance that heats the coloured alcohol in the glass vessel just above it. This causes some of the alcohol to vapourise, the pressure pushing the liquid up the connecting pipe to the vessel at top right. As the latter gets heavier the wheel bearing the four vessels experiences a torque that rewinds a remontoire* spring driving a conventional gear train and escapement. This clock has a pendulum-controlled escapement, but models with balance wheel escapements also existed.

The firm of Jauch and Schmid was registered in 1930

The images in this section were very kindly provided by John Howell.

*A remontoire, from the French 'remonter' (to rewind) is a spring or gravity reserve of power that can be configured to give a near-constant driving torque because it is rewound at frequent intervals from another power source- usually this was a mainspring, whose own torque would slowly decrease as it unwound. The idea was that rewinding a spring or lifting a weight at relatively frequent intervals isolated the escapement from the variable torque of the mainspring.

Left: Advertising material for the Puja clock movement.

The clock shown here has a balance-wheel escapement attached instead of a pendulum.

To save you the trouble of grappling with a German-English dictionary, here are the translations of the salient words in the advert above; "wechselström" means "alternating current", "gleichström" means "direct current", "thermo-aufzug mit glaskolben-laufrad" translates as "thermo-lifter with glass bulb impeller", and "gehwerk" as "movement".

Gangreserve 6 stunden = power reserve 6 hours. Unruhwellen = balance shafts, and zugfedern = tension springs. I'm not too clear what the last two words are getting at; it looks like two different models, and perhaps refers to pendulum and balance-wheel versions.

Left: Another Puja clock movement

This clock also has a balance-wheel escapement attached over a hole where the pendulum would go.

It occurs to me that this arrangement must be very inefficient; it looks as though much of the heat would escape without doing anything useful. Presumably the translucent trough shown in the first picture helped to keep the heat in.

I also wonder if the Puja clocks were prone to catching fire.

This model is for 220V mains.

Left: Another Puja clock movement

This is a different clock, with differently-coloured alcohol and a neater escapement mounting. A modern wire-wound resistor has been fitted into the heater spring clips.


Anyone interested in oddly-powered clocks will have heard of the Atmos clock, which appears to be mostly powered by changes in temperature, and not, as its name might suggest, solely by changes in atmospheric pressure. A flexible metal capsule is filled with an inert gas and a little ethyl chloride, which vapourises as the temperature rises, causing the bellows to expand, and vice versa. A chain transfers this movement to wind the mainspring. A torsional pendulums with a long period is used to minimise the power required.

Left: An Atmos clock

A temperature variation of only one degree in the range between 15 and 30 degrees Celsius, or a pressure variation of 3 mmHg, is said to be sufficient for two days' operation. I don't know if it is the case, but that seems to imply that the clock would stop working if the temperature fell below 15 degrees and stayed there, with the ethyl chloride remaining liquid. This is of course very possible in Winter. I also wonder how it copes with thermostatically-controlled central heating.

The torsional pendulum makes only two oscillations per minute, which is 1/60th the rate of the standard seconds pendulum in a conventional clock. Because of the very slow movement of the gear train, no oil is used; it is claimed no measureable wear occurs.

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