(Read this article in Dutch.)

The sympiesometer designed
by Alexander Adie: an unusually short 'barometer' without mercury.

By: Marco Fontijn.

On December 27th in 1831, warship HMS Beagle set sail from Devonport in England under the command of Captain Robert Fitzroy (1805-65). The ship had embarked upon an expedition of discovery around the world that was to take five years. Fitzroy, not only a renowned captain and navigator, but also a most Biblically oriented young man, was convinced that this expedition would provide scientific evidence of the intrinsic truth of the Book of Genesis. However, contrary to Fitzroy's expectations, the opposite actually proved to be the case. For, with him was 26-year-old biologist/geologist, Charles Darwin (1809-82).

On November 15th 1835 the ship weighed anchor off one of the Galapagos Islands. There, during the course of Darwin's studies, it emerged that there existed an incredible variety of finches, distinguishable by differences in the shape of their beaks. According to Fitzroy's Creationist beliefs, God must have been particularly interested in finches as he had created such a variety of beaks for them in the archipelago. Interestingly, he had created a different type especially for each island. Yet Darwin's conclusion was a far more straightforward one: although related, the beaks of the finches in each location were adapted to the kind of food that was available there, according to principles of natural selection.

After many years of research, Darwin published: 'On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life' in November 1859. Predictably, Fitzroy, by this time a Rear Admiral, was very unhappy with this publication. He must have been particularly dismayed to have indirectly contributed to a school theory directly opposed to biblical doctrine. In 1860, unable to suppress his outrage, he disrupted a lecture on Darwin's theory. Waving a Bible he loudly exclaimed: "This is against God's word". Five years later, perhaps in despair, Fitzroy committed suicide, an act explicitly forbidden by his religion.

Fitzroy, however, is known to have been far less conservative in his attitudes regarding other scientific and ethical matters. In 1845, after two years service as Governor General of New Zealand, he was recalled to London after upsetting the colonists by refusing to support settlers in their attempts to dispossess Maoris of their land. He was also a notable pioneer in the field of meteorology. After retiring from active service in the navy he was made director of the newly established 'Meteorological Department of the Board of Trade' - nowadays known as the 'British Meteorological Office'. He established daily weather forecasts, set up the first storm-warning service and published: 'the Weather Book', in 1862.

Photo 1: English Sympiesometer circa 1840.
Inscribed: 'PATENT C. Cummins 148 Leadenhall Street LONDON'.


Since his earliest voyages, Fitzroy had been interested in the phenomena that preceded changes in the weather and in discovering how an understanding of these might be used for weather prediction. Needless to say, this required a great many specialist tools. For this purpose, a large collection of highly advanced instruments was carefully selected, packed in sawdust-filled crates and loaded aboard the Beagle. No fewer than 22 Chronometers were amongst the collection, which also included five examples of a special type of 'barometer' named the sympiesometer, which was especially favoured by Fitzroy. This relatively new invention, precluding the use of mercury, had been specially designed for maritime use and thoroughly tested on ships travelling in the Tropics, the Polar Regions, and off the Scottish coast. Fitzroy, no doubt, was aware of how successful the new sympiesometer had proven to be. In a letter from the captain of The Isabella - one of the ships of Ross's Arctic expedition of 1820 - can be found the following quote: "The Sympiesometer is a most excellent instrument, and shews the weather far better than the marine barometer. In short, the barometer is of no use compared to it…in my opinion it surpasses the mercurial barometer as much as the barometer is superior to having none at all."

Photo 3: Scottish marine barometer with sympiesometer, circa 1860-1870. Signed: 'Mc.GREGOR & Co GLASGOW & GREENOCK'.

Alexander Adie (1775-1858), from Edinburgh, a highly acclaimed maker of scientific instruments, was granted a patent for his sympiesometer in 1818 and published an extensive description of it a year later. The word 'sympiesometer' is derived from 'sumpiedzein' and 'metron', the Greek terms for compression and measurement respectively. Adie had a particular interest in meteorological instruments and was apprentice to his uncle, John Miller, a prominent Scottish instrument maker, becoming his partner in 1804. Until his death, Adie practiced his trade from a variety of locations in Edinburgh. In his 'British Patent 4323' (1818), Adie's instrument is described as 'An improvement on the air barometer'.
Adie's sympiesometer was actually an improvement upon Robert Hooke's thermobarometer. And, although the latter instrument had been around since the beginning of the 18th century, few were produced during the first decades.

One example is that of John Patrick, a famous English barometer maker, who described his new instrument, in an advertisement, as: 'A Ship Barometer A Foot Long'. More unusual than its unconventional length, was the omission of mercury as the medium for measurements. These barometers were responsive both to air pressure and temperature.

Hooke's thermobarometer consisted of a conventional closed alcohol thermometer, together with an open thermometer, which had air locked into the top end of its tube. The temperature was read from the scale beside the closed thermometer, and used to calculate the correction that was required in order to compensate for the effect of temperature upon the open thermometer, whose barometric scale indicated air pressure.

Photo 2: Diagram of the sympiesometer by Alexander Adie, 1818.
A = reservoir filled with hydrogen
C = reservoir filled with coloured almond oil
MN = sliding barometric scale
OP = temperature correction scale

As previously mentioned, Adie's barometer was designed to work - more or less - according to the same principle, as Hooke's instrument. The compression, referred to in the instrument's name, took place in the gas-filled reservoir, from which readings could be taken by means of coloured liquid, in this case almond oil. Instead of using air, Adie made use of hydrogen, which was at the other end of the tube, above the almond oil. Adie provided his instrument with a sliding temperature correction scale, which enabled the user to adjust the barometric scale to compensate for the effect of temperature upon the oil-filled tube, according to the thermometer reading. Hooke's thermobarometers had a similar sliding scale, but Adie's instrument was much narrower, simpler, and therefore easier in use.

Adie's original intention had been to create a barometer that would be easier in use and less cumbersome and fragile than existing maritime models, which consisted of a long mercury tube. In 1829, shortly before the famous voyage of HMS Beagle, the distinguished Scottish scientist James Forbes gave testimony to the success of Adie's invention: "As a marine barometer, its superiority in accuracy and utility, as well as convenience, seems fully established".

Adie's patented sympiesometers were inscribed either with his own name and a serial number or with the name of an agent especially appointed by him. In its sixty years of production, over 2500 sympiesometers were manufactured in this manner. However, Adie's patent expired after fifteen years and from then on others started to manufacture sympiesometers. Many versions were introduced in every conceivable size; the smallest of them a pocket-sized one. Although sympiesometers gained considerable popularity in the 19th century, they are now hard to come by and only found sporadically in the antique market.

Photo 4: close-up detail of the sympiesometer, as seen in photo 3.

Useful though it was, the sympiesometer proved to have some drawbacks. Firstly, it was inconvenient not to be able to take an instant reading. And, during transport, it was usually necessary to keep the instrument upright. The relatively short lifespan of the instrument also proved a major disadvantage. Over time, the hydrogen would gradually escape through the oil, resulting in a loss of accuracy. In addition, the almond oil was likely to eventually evaporate.

From around 1850 new alternatives were introduced, such as the new aneroid barometers and a type of greatly improved mercury ship's barometer, designed according to the 'Kew Marine' principle. Although the sympiesometer was superseded as a sole means of weather forecasting, it found a supplementary role alongside mercury ship's barometers, enabling a comparison in readings between either instrument in situations where extremely accurate observations were required.

Photograph no. 3 shows an example of a ship's barometer, provided with supplementary sympiesometer, signed 'D. Mc. GREGOR & Co GLASGOW & GREENOCK'. Made between 1860 and 1870, the instrument's strikingly narrow oak case is fitted with faceted glass to protect the scale plates. The barometer scale plates are of ivory and fitted with two rack-operated verniers. Its mercury tube is tapered in order to prevent the mercury surging during rough weather. The palm wood reservoir has a leather bottom and is protected by a brass cover. It has a control screw that closes the reservoir for the purpose of transportation.
The sympiesometer, situated below the gimbals, has a silvered brass scale plate. Protruding through its case, on the top left, is a knurled control wheel that enables the user to refer back to the registered reading on the barometric scale. On the right of the case is the control used to set the vernier.

Photograph no. 1 also illustrates an unusual and fairly early sympiesometer, by Charles Cummins, designed shortly after 1840. In the same year, this London instrument maker was granted a patent (British patent 8462) for a sympiesometer differing in shape from that by Adie and, moreover, using sulphuric acid rather than almond oil. The case is of solid mahogany and a flat glass protects the silvered brass scale plates. The mercury thermometer measures in degrees Fahrenheit and the barometric scale plate moves up and down by operating a brass sliding control, mounted on the right of the case. On this slide there is a brass knob used to set the rack-operated vernier.

(Translation: Sonja Fenton)

Go to Dutch version of this article