16-11-2012, 01:19 PM
John Dalton
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Early life
John Dalton was born into a Quaker family at Eaglesfield, near Cockermouth,Cumberland, England. The son of a weaver, he joined his older brother Jonathan at age 15 in running a Quaker school in nearby Kendal. Around 1790 Dalton seems to have considered taking up law or medicine, but his projects were not met with encouragement from his relatives – Dissenters were barred from attending or teaching at English universities – and he remained at Kendal until, in the spring of 1793, he moved toManchester. Mainly through John Gough, a blind philosopher and polymath to whose informal instruction he owed much of his scientific knowledge, Dalton was appointed teacher of mathematics and natural philosophy at the "New College" in Manchester, a dissenting academy. He remained in that position 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.
Dalton's early life was highly influenced by a prominent Eaglesfield Quaker named Elihu Robinson,[1] a competent meteorologist and instrument maker, who got him interested in problems of 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 ameteorological diary in which, during the succeeding 57 years, he entered more than 200,000 observations.[2] He also rediscoveredGeorge Hadley's theory of atmospheric circulation (now known as the Hadley cell) around this time.[3] Dalton's first publication wasMeteorological Observations and Essays (1793), which 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. A second work by Dalton, Elements of English Grammar, was published in 1801.
Atomic theory
In 1800, 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 othervapours 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.
Atomic weights
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.[citation needed] However, in his laboratory notebook under the date 6 September 1803[6] 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.
Five main points of Dalton's atomic theory
Public and personal life
Before he had propounded the atomic theory, he had already attained a considerable scientific reputation. In 1804, he was chosen to give a course of lectures on natural philosophy at the Royal Institution in London, where he delivered another course in 1809–1810. However, some witnesses reported that he was deficient in the qualities that make an attractive lecturer, being harsh and indistinct in voice, ineffective in the treatment of his subject, and singularly wanting in the language and power of illustration.
Death and legacy
Dalton suffered a minor stroke in 1837, and a second one in 1838 left him with a speech impediment, though he remained able to do experiments. In May 1844 he had yet another stroke; on 26 July he recorded with trembling hand his last meteorological observation. On 27 July, in Manchester, 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.[9] He was buried in Manchester in Ardwick cemetery. The cemetery is now a playing field, but pictures of the original grave are in published materials.[10][11]