John Dalton

Eaglesfield

John Dalton was born on 6 September 1766 in Eaglesfield, a village near Cockermouth in Cumberland. His father Joseph was a weaver. His mother Deborah came from the Greenup family. They were Quakers, and they were poor. The cottage had a hand loom in it. The education was basic. The ambition, by the standards of Georgian Cumberland, was supposed to be limited.

It wasn't. By the age of 12, Dalton was teaching at the local school. He stood in front of children not much younger than himself and taught them what he knew, which was already more than most of the adults in the village. He earned almost nothing. But a wealthy Quaker in the village, a man called Elihu Robinson, noticed him. Robinson was an instrument maker, a meteorologist, and a serious amateur scientist. He took the boy under his wing, taught him mathematics and weather observation, and set him on the path that led to everything else.

At around 15, he and his older brother Jonathan became assistants at a Quaker boarding school in Kendal, about 40 miles to the south. By 19, John and Jonathan were running it together. He taught there for over a decade, studying mathematics and science in his spare time, guided by a blind philosopher called John Gough who taught him meteorology, botany, and the habit of looking at the world as something to be measured rather than simply accepted.

On 24 March 1787, aged 21 and still in Kendal, Dalton started a weather diary. He would keep it for 57 years, from Westmorland to Manchester and everywhere in between. He made his last entry on 26 July 1844, the day before he died. Over 200,000 observations across a lifetime. He went outside at the same times and wrote down what the sky was doing. A neighbour in Manchester reportedly set her clock by his appearances at the door.

Manchester

In 1793, Dalton moved to Manchester. He was 26. He had been appointed to teach mathematics and natural philosophy at New College, a dissenting academy on Mosley Street. Dissenting academies existed because Oxford and Cambridge wouldn't admit anyone who wasn't Church of England. If you were a Quaker, a Methodist, a Baptist, a Unitarian, or anything else, you went to a dissenting academy or you went nowhere. Manchester's was one of the best in the country.

He brought with him the proofs of his first book, Meteorological Observations and Essays, which was published that year. He was already obsessed with the atmosphere. Why did it rain? Why did lakes evaporate? Why did different gases behave differently at different temperatures? These were not idle questions. They led him to the most important idea of his life.

New College's finances collapsed around the turn of the century, and Dalton left. He never took another institutional post. Instead, he became a private tutor, teaching the children of Manchester's merchant families from his lodgings. He lived at 10 George Street from 1804, sharing rooms with his friend the Reverend William Johns, then moved to Faulkner Street around 1830. It was not glamorous. But it gave him time to think, and Manchester gave him somewhere to do it.

That somewhere was the Manchester Literary and Philosophical Society, the Lit & Phil, which had its premises at 36 George Street. Dalton was elected a member on 17 October 1794. He became Secretary, then Vice-President, then President. He read 117 papers to the Society over his lifetime. They gave him a laboratory in the building, and that is where he did his most important work. The Lit & Phil was founded in 1781, making it the oldest surviving such society in the world. And its most famous member was the quiet Quaker who came down from the Lakes with a weather diary and made Manchester the place where modern chemistry was born.

The Weather and the Atoms

The path from weather to atoms is not obvious, but for Dalton it was a straight line. He started by trying to understand why the atmosphere worked the way it did. Why did water vapour mix with air instead of sitting on top of it? Why did gases diffuse into each other? He spent years measuring, calculating, and testing.

In October 1801, he presented a series of essays to the Lit & Phil that contained what became known as Dalton's Law of Partial Pressures: the total pressure of a mixture of gases is simply the sum of the pressures each gas would exert on its own. It sounds simple. It is simple. But nobody had stated it clearly before, and the implications were enormous. It meant that gases behaved as if the other gases in a mixture did not exist. Each gas acted independently. That could only work if gases were made of individual particles that didn't interact with each other.

By 1803, Dalton had taken the next step. He proposed that all matter is made up of tiny, indivisible particles called atoms. That atoms of a given element are identical in mass and properties. That atoms of different elements have different masses. And that atoms combine in simple, whole-number ratios to form compounds. One atom of this, two atoms of that. Not half an atom. Not three-quarters. Whole numbers.

He published the theory in A New System of Chemical Philosophy, the first volume appearing in 1808. It included a table of atomic weights, the first anyone had ever drawn up. Some of his weights were wrong. His model of how atoms combined was sometimes mistaken. But the core idea, that matter is made of atoms and that chemistry is the business of rearranging them, was right. It is the foundation of modern chemistry. Every chemical equation, every molecular diagram, every drug, every material, every industrial process that depends on understanding what things are made of traces back to a Quaker schoolteacher working in a laboratory at the Lit & Phil on George Street, Manchester.

The Man Who Couldn't See Red

Dalton's very first paper to the Lit & Phil, presented on 31 October 1794, had nothing to do with atoms. It was called "Extraordinary Facts Relating to the Vision of Colours," and it was about something he had noticed in himself. He couldn't tell red from green. A scarlet coat looked the same colour as the trees behind it. Pink and blue were interchangeable. His brother had the same condition.

Nobody had ever described this systematically before. Dalton did. He tested himself, he tested others, he recorded everything, and he published it. The condition became known across Europe as Daltonism, and the name stuck. In France, Italy, and much of the world, colour blindness is still called Daltonism to this day.

Dalton had a theory about why it happened. He believed his vitreous humour, the jelly inside his eyeball, was tinted blue, filtering out certain wavelengths of light before they reached his retina. He was so confident in this theory that he left instructions for his eyes to be examined after his death.

They were. When he died in 1844, his physician Joseph Ransome dissected one eye and preserved both. The vitreous humour was perfectly clear. His theory was wrong. But his description of the condition was right, and the eyes sat in a jar at the Manchester Literary and Philosophical Society for the next 150 years.

In 1995, a team from Cambridge and the Institute of Ophthalmology in London extracted DNA from the preserved eye tissue, supplied by the Lit & Phil, and analysed it. They found that Dalton lacked the gene for the medium-wavelength photoreceptor, the one that detects green light. He had deuteranopia. The mystery he had first described to the Lit & Phil in 1794 was finally solved 201 years later, using his own eyes.

Forty Thousand People

John Dalton died on 27 July 1844, in Manchester, aged 77. He had suffered three strokes, the first in 1837, the second in 1838, and a final one in May 1844. He had never married. He had never been rich. He had lived in Manchester for over 50 years, measuring the same sky, doing the same work, asking the same kinds of questions.

His body was laid in state at the old Town Hall on King Street. Over four days, approximately 40,000 people filed past to pay their respects. For a Quaker who valued simplicity and whose faith discouraged public ceremony, it was an extraordinary send-off. The funeral procession on 12 August 1844 stretched through the streets of Manchester. He was buried at Ardwick Cemetery. The cemetery was cleared in the 1950s and is now playing fields. The grave is gone.

Manchester remembered him anyway. A statue by Francis Chantrey, commissioned by public subscription in 1834 and completed in 1838, originally stood in the entrance hall of the Royal Manchester Institution on Mosley Street. When the current Town Hall opened in Albert Square in 1877, the statue was moved there, where it stands today. A second statue, by William Theed, was erected in Piccadilly in 1855 and moved in 1966 to what is now Manchester Metropolitan University's campus on Chester Street. The university's John Dalton Building carries his name. So does a street in the city centre, John Dalton Street, running from Deansgate to Albert Square.

The Lit & Phil still exists. It is the oldest surviving literary and philosophical society in the world, and John Dalton is the reason most people have heard of it. His preserved eyes, after 150 years at the Society, were transferred to the Science Museum Group in 1997 and are now in the care of the Science and Industry Museum in Manchester. The jar, the DNA, the 201-year gap between the question and the answer. All of it, still in this city.

He arrived in 1793, a 26-year-old schoolteacher from a Cumberland village, with a weather diary and a book about rain. He gave us the atom. He described colour blindness using his own eyes. He measured the sky for 57 years and never stopped. He changed how we understand matter, and he did it from a laboratory at the Lit & Phil on George Street.

A weaver's son from Eaglesfield who taught himself everything. That's a Manchester legend.