John Dalton

John Dalton (5 or 6 September 1766 – 27 July 1844) was an English chemist, physicist and meteorologist.

He introduced the atomic theory into chemistry.

He also researched colour blindness, which he had; as a result, colour blindness is known as Daltonism in several languages.

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

His father was a weaver.

He received his early education from his father and from Quaker John Fletcher, who ran a private school in the nearby village of Pardshaw Hall.

Dalton's family was too poor to support him for long and he began to earn his living, from the age of ten, in the service of wealthy local Quaker Elihu Robinson.

When he was 15, Dalton joined his older brother Jonathan in running a Quaker school in Kendal, Westmorland, about 45 mi from his home.

Around the age of 23, Dalton may have considered studying law or medicine, but his relatives did not encourage him, perhaps because being a Dissenter, he was barred from attending English universities.

He acquired much scientific knowledge from informal instruction by John Gough, a blind philosopher who was gifted in the sciences and arts.

At 27, he was appointed teacher of mathematics and natural philosophy at the "Manchester Academy" in Manchester, a dissenting academy (the lineal predecessor, following a number of changes of location, of Harris Manchester College, Oxford).

He remained for seven years, until the college's worsening financial situation led to his resignation.

Dalton began a new career as a private tutor in the same two subjects.

Dalton's early life was influenced by a prominent Quaker, Elihu Robinson, a competent meteorologist and instrument maker, from Eaglesfield, Cumberland, who interested him in problems of mathematics and meteorology.

During his years in Kendal, Dalton contributed solutions to problems and answered questions on various subjects in The Ladies' Diary and the Gentleman's Diary.

In 1787 at age 21 he began his meteorological diary in which, during the succeeding 57 years, he entered more than 200,000 observations.

He rediscovered George Hadley's theory of atmospheric circulation (now known as the Hadley cell) around this time.

In 1793 Dalton's first publication, Meteorological Observations and Essays, contained the seeds of several of his later discoveries but despite the originality of his treatment, little attention was paid to them by other scholars.

In 1794, shortly after his arrival in Manchester, 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 colour perception was caused by discoloration of the liquid medium of the eyeball.

As both he and his brother were colour blind, he recognised that the condition must be hereditary.

Although Dalton's theory was later disproven, his early research into colour vision deficiency was recognized after his lifetime.

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

A second work by Dalton, Elements of English Grammar (or A new system of grammatical instruction: for the use of schools and academies), was published in 1801.

After leaving the Lake District, Dalton returned annually to spend his holidays studying meteorology, something which involved a lot of hill-walking.

Until the advent of aeroplanes and weather balloons, the only way to make measurements of temperature and humidity at altitude was to climb a mountain.

Dalton estimated the height using a barometer.

The four essays, presented between 2 and 30 October 1801, were published in the Memoirs of the Literary and Philosophical Society of Manchester in 1802.

The second essay opens with the 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 0 and 100 °C (32 and 212 °F), Dalton concluded from observations of 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 the fourth essay he remarks,

"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."

Otley published his information in his map of 1818.

Otley became both an assistant and a friend to Dalton.

The Ordnance Survey did not publish maps for the Lake District until the 1860s.

Before then, Dalton was one of the few authorities on the heights of the region's mountains.

He was often accompanied by Jonathan Otley, who also made a study of the heights of the local peaks, using Dalton's figures as a comparison to check his work.

Examination of his preserved eyeball in 1995 demonstrated that Dalton had deuteranopia, a type of congenital red-green color blindness in which the gene for medium wavelength sensitive (green) photopsins is missing.

Individuals with this form of colour blindness see every colour as mapped to blue, yellow or gray, or, as Dalton wrote in his seminal 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."