The chemist and physicist known for his research into color blindness is perhaps best known for his pioneering work in the development of modern atomic theory. Now WE know em


John Dalton was born September 6, 1766 into a Quaker family at Eaglesfield, near Cockermouth, Cumberland, England.

The son of a weaver, by the age of 15 John had joined his older brother in running a Quaker school in nearby Kendal.

John’s early life became highly influenced by a prominent Eaglesfield Quaker named Elihu Robinson, who was a competent meteorologist and instrument maker, and the man that sparked an interest in John in regard to mathematics and meteorology.

During his years in Kendal, Dalton contributed solutions of problems and questions on various subjects to the Gentlemen’s and Ladies’ Diaries, and in 1787 he began to keep a meteorological diary in which, during the succeeding 57 years, he entered more than 200,000 observations.

John also rediscovered George Hadley’s theory of atmospheric circulation (now known as the Hadley cell) around this time.

Around 1790, he considered taking up law or medicine, but these dreams were not met with encouragement from his relatives.

In 1793, John Dalton’s was published for the first time in Meteorological Observations and Essays.

This article contained the seeds of several of his later discoveries.

However, in spite of the originality of his treatment, little attention was paid to them by other scholars.

So in the spring of 1793, John moved to Manchester.

Mainly through John Gough, a blind philosopher and polymath to whose informal instruction he owed much of his scientific knowledge, John Dalton was appointed teacher of mathematics and natural philosophy at the “New College” in Manchester.

Color blindness

In 1794, shortly after his arrival in Manchester, John Dalton was elected a member of the Manchester Literary and Philosophical Society, the “Lit & Phil”, and a few weeks later he communicated his first paper on “Extraordinary facts relating to the vision of colours”, in which he postulated that shortage in color perception was caused by discoloration of the liquid medium of the eyeball.

In fact, a shortage of color perception in some people had not even been formally described or officially noticed until John wrote about his own.

Since both he and his brother were color blind, he recognized that this condition must be hereditary.

Although John’s theory lost credence in his own lifetime, the thorough and methodical nature of his research into his own visual problem was so broadly recognized that Daltonism became a common term for color blindness.

Examination of John Dalton’s actual preserved eyeball in 1995 demonstrated that he actually had a less common kind of color blindness, deuteroanopia, in which medium wavelength sensitive cones are missing (rather than functioning with a mutated form of their pigment, as in the most common type of color blindness, deuteroanomaly).

Besides the blue and purple of the spectrum, John was able to recognize only one color, yellow, or, as he said in a paper;

“that part of the image which others call red appears to me little more than a shade or defect of light. After that the orange, yellow and green seem one colour which descends pretty uniformly from an intense to a rare yellow, making what I should call different shades of yellow”

This paper was followed by many others on diverse topics such as rain and dew and the origin of springs, on heat, the color of the sky, steam, the auxiliary verbs and participles of the English language and the reflection and refraction of light.

John remained at New College until 1800, when the college’s worsening financial situation led him to resign his post and begin a new career in Manchester as a private tutor for mathematics and natural philosophy.

A second work by John Dalton, Elements of English Grammar, was published in 1801.

Then in 1800, John Dalton became a secretary of the Manchester Literary and Philosophical Society, and in the following year he orally presented an important series of papers, entitled “Experimental Essays” on the constitution of mixed gases; on the pressure of steam and other vapours at different temperatures, both in a vacuum and in air; on evaporation; and on the thermal expansion of gases.

These four essays were published in the Memoirs of the Lit & Phil in 1802.

The second of these essays opened with this striking remark;

“There can scarcely be a doubt entertained respecting the reducibility of all elastic fluids of whatever kind, into liquids; and we ought not to despair of effecting it in low temperatures and by strong pressures exerted upon the unmixed gases further.”

After describing experiments to ascertain the pressure of steam at various points between 32 and 212 °F, Dalton concluded from observations on the vapour pressure of six different liquids, that the variation of vapour pressure for all liquids is equivalent, for the same variation of temperature, reckoning from vapour of any given pressure.

In a fourth essay John remarked;

“I see no sufficient reason why we may not conclude that all elastic fluids under the same pressure expand equally by heat and that for any given expansion of mercury, the corresponding expansion of air is proportionally something less, the higher the temperature. It seems, therefore, that general laws respecting the absolute quantity and the nature of heat are more likely to be derived from elastic fluids than from other substances.”

John Dalton thus enunciated Gay-Lussac’s law or J.A.C. Charles’s law, published in 1802 by Joseph Louis Gay-Lussac.

In the two or three years following the reading of these essays, John Dalton published several papers on similar topics, that on the absorption of gases by water and other liquids (1803), containing his law of partial pressures now known as Dalton’s law.

Today, the most important of all John Dalton’s investigations are those concerned with the atomic theory in chemistry, with which his name is inseparably associated.

It has been proposed that this theory was suggested to him either by researches on ethylene (olefiant gas) and methane (carburetted hydrogen) or by analysis of nitrous oxide (protoxide of azote) and nitrogen dioxide (deutoxide of azote), both views resting on the authority of Thomas Thomson.

However, a study of John Dalton’s own laboratory notebooks, discovered in the rooms of the Lit & Phil, concluded that he was being led in his search for an explanation of the law of multiple proportions to the idea that chemical combination consists in the interaction of atoms of definite and characteristic weight, were ideas about atoms that arose in his mind as a purely physical concept, forced upon him by his study of the physical properties of the atmosphere and other gases.

The first published indications of this idea are to be found at the end of his paper on the absorption of gases already mentioned, which was read on October 21, 1803, though not published until 1805.

Here John Dalton said:

“Why does not water admit its bulk of every kind of gas alike? This question I have duly considered, and though I am not able to satisfy myself completely I am nearly persuaded that the circumstance depends on the weight and number of the ultimate particles of the several gases.”

John Dalton proceeded to print his first published table of relative atomic weights. Six elements appear in this table, namely hydrogen, oxygen, nitrogen, carbon, sulfur, and phosphorus, with the atom of hydrogen conventionally assumed to weigh 1.

Dalton provided no indication in this first paper how he had arrived at these numbers. However, in his laboratory notebook under the date September 6, 1803 there appears a list in which he sets out the relative weights of the atoms of a number of elements, derived from analysis of water, ammonia, carbon dioxide, etc. by chemists of the time.

It appears, then, that confronted with the problem of calculating the relative diameter of the atoms of which, he was convinced, all gases were made, he used the results of chemical analysis.

Assisted by the assumption that combination always takes place in the simplest possible way, he thus arrived at the idea that chemical combination takes place between particles of different weights, and it was this which differentiated his theory from the historic speculations of the Greeks, such as Democritus and Lucretius.

The extension of this idea to substances in general necessarily led him to the law of multiple proportions, and the comparison with experiment brilliantly confirmed his deduction.

John Dalton then hypothesized the structure of compounds can be represented in whole number ratios. So, one atom of element X combining with one atom of element Y is a binary compound. Furthermore, one atom of element X combining with two elements of Y or vice versa, is a ternary compound.

Many of the first compounds listed in the New System of Chemical Philosophy correspond to modern views, although many others do not.

The Five main points of John Dalton’s atomic theory:

  1. Elements are made of extremely small particles called atoms.
  2. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
  3. Atoms cannot be subdivided, created, or destroyed.
  4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
  5. In chemical reactions, atoms are combined, separated, or rearranged.

Despite the uncertainty at the heart of John Dalton’s atomic theory, the principles of the theory survived.

To be sure, the conviction that atoms cannot be subdivided, created, or destroyed into smaller particles when they are combined, separated, or rearranged in chemical reactions is inconsistent with the existence of nuclear fusion and nuclear fission, but such processes are nuclear reactions and not chemical reactions.

However, John Dalton had created a theory of immense power and importance. Indeed, his innovation was fully as important for the future of the science as Antoine Laurent Lavoisier’s oxygen-based chemistry had been.

John was president of the Lit & Phil from 1817 until his death, contributing 116 memoirs.

Of these the earlier are the most important.

In 1810, Sir Humphry Davy asked John Dalton to offer himself as a candidate for the fellowship of the Royal Society, but Dalton declined, possibly for financial reasons.

However, in 1822 he was proposed without his knowledge, and on election paid the usual fee.

In 1833, Earl Grey’s government conferred on John a pension of £150, raised in 1836 to £300.

Dalton never married and had only a few close friends, all in all as a Quaker he lived a modest and unassuming life.

He lived for more than a quarter of a century with his friend the Rev. W. Johns, on George Street, Manchester, where his daily round of laboratory work and tuition was broken only by annual excursions to the Lake District and occasional visits to London.

John Dalton suffered a minor stroke in 1837, and a second one in 1838 that left him with a speech impediment, though he remained able to do experiments.

In May 1844 he had yet another stroke, and on July 26th, he recorded with trembling hand his last meteorological observation.

Then on July 27, 1844, in Manchester, John Dalton fell from his bed and was found lifeless by his attendant.

Approximately 40,000 people filed by his coffin as it was laid in state in the Manchester Town Hall.

He was buried in Manchester in Ardwick cemetery.

A bust of John Dalton, by Chantrey, was publicly subscribed for and placed in the entrance hall of the Royal Manchester Institution. Chantrey also crafted a large statue of Dalton, now in the Manchester Town Hall. The statue was erected while Dalton was still alive and it has been said: “He is probably the only scientist who got a statue in his lifetime”.

Statue of John Dalton in the Manchester Town Hall.

Statue of John Dalton in the Manchester Town Hall.

In honour of Dalton’s work, many chemists and biochemists today use the (as yet unofficial) unit dalton (abbreviated Da) to denote one atomic mass unit, or 1/12 the weight of a neutral atom of carbon-12.

A lunar crater has been named after John Dalton.

“Daltonism” became a common term for color blindness and “Daltonien” is the actual French word for “colour blind”.

Much of his collected work was damaged during the bombing of the Manchester Literary and Philosophical Society on December 24, 1940. This event prompted Isaac Asimov to say, “John Dalton’s records, carefully preserved for a century, were destroyed during the World War II bombing of Manchester. It is not only the living who are killed in war”.

The damaged papers are now in the John Rylands Library having been deposited in the university library by the Society.

Now WE know em



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