Rare mercury thermometer made by Daniel Fahrenheit in early 1700s set to fetch £100,000 at auction



Device is just one of three made by scientist to be found



Prior to discovery it was thought only two originals existed

It has been in private collection for over 40 years



Mercury thermometer with Fahrenheit scale: One of Daniel Gabriel Fahrenheit's original thermometers that was thought to have been lost has now emerged

An original thermometer invented by Daniel Gabriel Fahrenheit is set to fetch £100,000 at auction.

It was thought the mercury thermometer, created in the early 1700s, had been lost in history.



Prior to the discovery of the 300-year-old brass instrument, only two originals were known to exist - both in a museum in the Netherlands.

But now this third, signed example, has got collectors hot under the collar as it is set to be sold at a London auction.

Fahrenheit invented the mercury thermometer in 1714, but it is unknown exactly how many he made and when.



His other great invention was the Fahrenheit scale that is still used today, and which the 4.5 inch-long thermometer is annotated with.

The scale on the newly-discovered thermometer is marked from '0' to '132' degrees Fahrenheit and it is so small that the numbers had to be written on both sides of the mercury tube.

It had been in a private collection for over 40 years.

The device is signed 'Fahrenheit Amst', from the time the inventor worked in Amsterdam, where he made the device.

It is thought the thermometer was owned by a great scientist of the time.

James Hyslop, from auctioneers Christie’s, which is selling the relic, said: 'Until now, only two originals were thought to exist.

'And these are both in the Boerhaave Museum in the Netherlands.



'So to have this one emerge is very exciting.



'It is impossible to pinpoint exactly when it was made, but one in the museum is dated 1718, and this was probably made between 1715 and 1730.



'He made barometers with thermometers on the side, but this was one was a special scientific thermometer.



'It is only 4.5 inches long and is made of brass and has the Fahrenheit scale down the sides.



'The mercury tube is not the original and has been replaced, but it was clearly designed so the tubes could be taken out.

'It was a thermometer for scientific purposes perhaps for measuring the temperature of liquids.



'Originally it was probably owned by a great scientist of the day, but we don't know it might have been.

'It is signed “Fahrenheit Amst”, from the time he worked in Amsterdam.

'People are very excited by it and we hope that museums might come in and bid for it.'



The auction takes place on October 9.

Signed by the inventor: He has marked the thermometer with 'Amst', short for Amsterdam, where he made the device