John Dalton: atoms, eyesight and auroras

Early years and the move to Manchester

Dalton was born in what is now Cumbria in 1766. He became principal at a local Quaker school and taught there until 1793, at which time he moved to Manchester to tutor in natural philosophy and science at the Manchester Academy, a Presbyterian college. 

However, his teaching duties left him with too little time to pursue his own scientific interests, so he became a private tutor, including to a budding young scientist called James Prescott Joule (more on whom later).

Joining the 'Lit & Phil'

Soon after moving to Manchester, Dalton joined the Literary & Philosophical Society, which was at the centre of the city's scientific and business community. It was a discussion group set up to share scientific ideas at a time when science had yet to become a profession.

The Society gave him a room for teaching and research at its premises on George Street. Through this, he gained access to a well-equipped research laboratory, where his scientific output flourished.

Though sometimes criticised for the quality of his experiments, Dalton was an enthusiastic investigator who worked late most evenings. He read over 100 papers to the Society, and became its Secretary, Vice-President and, ultimately, President.

Through his experimentation, Dalton not only formulated a new atomic theory to explain chemical reactions, upon which much of modern chemistry and physics is based, but he also developed a theory to explain colour vision deficiency, from which he himself suffered. He was also a figurehead in the world of meteorology.

© The Board of Trustees of the Science Museum Image source for A patterned cloth cap with long sides that cover the ears

Dalton was interested in the composition of the atmosphere and, by extension, in how components mix together to form gases. He formulated the Law of Partial Pressures in 1801, according to which the pressure of a mixed gas is the sum of the pressures that each of its components would exert if occupying the same space. He also developed the law of the thermal expansion of gases. 

Henry Roscoe, a later Manchester chemist, suggested that Dalton was trying to explain why the constituents of a gaseous mixture remain homogeneously mixed instead of separating into layers according to their density, the understanding of which is particularly important in atmospheric studies.

Wellcome Collection, CC-BY Image source for Diagram of Simple and Compound Atmosphere

At the end of an 1803 paper on the absorption of gases by liquids, Dalton rather casually set out the first table of atomic weights. Encouraged by the favourable reception this paper received, he developed his theory further, in lectures to the Royal Society in 1803–04 and later in his New System of Chemical Philosophy:

Dalton's theory was based on the concept that each element consists of its own unique brand of indivisible atom; atoms of one element are all alike but they differ from atoms of other elements. Importantly, Dalton assigned atomic weights to the atoms of the 20 elements he knew of at the time. This was a revolutionary concept for the day, which would contribute to the development of the periodic table of the elements later in the 19th century.

Science Museum Group Collection

The below images are reproductions of drawings of atomic formulae by John Dalton, copied from original lent to the Science Museum Group by Manchester Literary and Philosophical Society.

Why was Dalton's work in atomic theory so pioneering?

This concept, that atoms of different elements are distinguished by differences in their weights, opened up new fields of experimentation. Each aspect of Dalton's theory has since been amended or refined, but its overall picture remains as the basis of modern chemistry and physics.

Through his work, Dalton also pioneered the use of ball-and-stick models to illustrate the three-dimensional structure of molecules, which are often used in teaching to this day.

We know when and why Dalton had these models made, because he describes their production and use in a letter written in 1842, two years before his death:

Contemporary critics doubted Dalton's atomic theory and his structural, three-dimensional thinking, as it was far beyond the perceived wisdom of the time. However, his ideas ultimately became fundamental to modern chemistry.

In addition to his work with atoms, Dalton also developed a theory to explain colour vision deficiency (or colour blindness), from which he himself suffered. He suggested that the colour of the fluid in the eyes, known as the vitreous humour, acted as a filter to certain colours in the spectrum.

Dalton’s ideas were met with resistance from some of his contemporaries at the time, so to test his theory, Dalton donated his eyes for examination after death. On 28 July 1844, the day after he died, local doctor Joseph Ransome performed the autopsy. 'Perfectly colourless' was the result, proving his theory to be incorrect. 

DNA analysis carried out in 1995 and published in the journal Science, 150 years after his death, revealed that Dalton lacked the gene for the receptor sensitive to medium wavelength (green) light, and in fact suffered from deuteranopia, or red-green colour blindness—a condition still referred to as Daltonism.

The eyes were retained by the Literary & Philosophical Society and donated to the museum in 1997. 
 

In addition to transforming our understanding of chemistry and colour blindness, Dalton was also a fervent weather watcher, becoming an important figure in the field of meteorology. He kept a daily weather diary, producing a detailed record of local weather conditions over 57 years—over 200,000 entries in total. Even in poor health, he continued to journal about the weather, and made his final entry mere hours before his death on 27 July 1844.

© The Board of Trustees of the Science Museum Image source for Two leather bound books, one on top of the other

As well as the classic Mancunian wind and rain, he also documented sightings of the aurora borealis, becoming enthralled by the 'glowing canopy' of light that occasionally appeared in the skies above the Lake District and Manchester.

You can read more about Dalton's obsession with the weather, particularly his work around the aurora borealis and its causes, on the Science and Industry Museum blog, and more on how space weather affects the Earth over on the website of our sister museum, the Science Museum:

John Dalton was widely honoured in his lifetime. He was elected one of the eight foreign associates of the French Academie des Sciences, a Fellow of the Royal Society and their first Royal Medallist. Oxford and Cambridge Universities both gave him honorary degrees. 

Dalton was especially loved by the people of Manchester, so much so that the city paid for a life-size statue to be erected during his lifetime, which can be found in the Town Hall. Upon his death, 40,000 people filed past his coffin as he lay in state, and there were 100 carriages in his funeral procession. 

Dalton is now regarded as a rather poor experimenter. However, he had a powerful and vivid pictorial imagination that often gave him profound insights, as exemplified in his work.

Dalton was extremely dedicated to his work and as a result became rather reclusive, remaining unmarried throughout his life and with few friends to speak of. He did, however, have a lasting impact on another 19th-century scientific pioneer: James Joule.

Science Museum Group Collection

James Prescott Joule (1818–89) is revered as one of the greatest scientists in the history of physics, due to his groundbreaking work in thermodynamics. He was the son of a renowned local brewer and grew up fascinated by all things scientific, and was fortunate enough to be tutored by John Dalton. 

Find out more about Joule and his own work here.