DALTON, NATURAL PHILOSOPHER
Raymond J. Seeger
(NSF Retired)
4507 Wetherill Road
Bethesda, Maryland 20816



From: PSCF 38 (September 1986): 210-211.

John Dalton (1766-1844) was born of simple Quaker folk in Eaglesfield (near Cockermouth). His father Joseph was a weaver of cheap woolen goods; his mother Deborah Greenup had three children that survived, of which John was the youngest. After going to the Pardshaw School, at twelve he was teaching in his own school. Three years later he assisted his cousin George Bewley in the neighboring Kendal school, which he and his brother Jonathan took over in 1785. Meanwhile, he met John Gough, the blind son of a wealthy tradesman, who helped him with Latin and Greek, mathematics and natural philosophy, but, above all, with the use of various measuring instruments. He himself began, at twentyone, a daily diary of weather observations (thermometer, barometer, hydroscope), which he continued until his death. Dalton was largely self-taught. At twenty-seven he became a teacher of mathematics at the New (Presbyterian) College in Manchester. At the same time he published "Meteorological Essays and Observations." In 1799 he devoted himself wholly to tutoring for Dissenters.

In 1796 Dalton became a life-long member of the Manchester Literary and Philosophical Society (President from 1817 on). He made his first presentation that very year on "Extraordinary Facts Relating to the Vision of Colours" (he had discovered his own color blindness in 1792). His second paper (1799) dealt with meteorology. In 1801 he published a practical "Elements of English Grammer."

Meanwhile, in 1795, having seen some lecture demonstrations, he became interested in the chemistry of gases. His own speculations about Greek atomism led to "A New System of Chemical Philosophy" (1808, 1810). This work, however, was not generally appreciated until about 1815, and then first by the French Acad6mie des Sciences, which made him a Corresponding Member (a Foreign Associate in 1830). Not until 1822 was he made a Fellow of the Royal Society; the same year he was welcomed with open arms by
the scientists in Paris. In 1826, however, the Royal Society did give him a George IV gold medal for his work on atomic theory. In 1832 he was awarded a D.C.L. by Oxford and an L.L.D. by the University of Edinburgh. Other honor societies, namely, Berlin, Moscow and Munich, paid tribute to his investigations. In 1833 the government finally granted him a pension of one hundred and fifty pounds per year (doubled three years later). The following year a bust of Dalton was made for a statue in the main entrance of Manchester Hall and later a bronze replica for the Infirmary Square. At his public funeral there were one hundred
carriages and 40,000 spectators. He was buried in Ardwick cemetery.

A Quaker bachelor, Dalton led a quiet life. He was straightforward, devoted to duty, and persevering. There was no pretence to good breeding; at times he was more abrupt and candid in speech than good manners would allow. He had no interest in general reading and even opposed having a library associated with the Manchester Literary and Philosophical Society. He was precise in money matters, had simple tastes and frugal habits. He played bowls once a week and would occasionally joke with friends. He liked to walk in
the mountains of his own lake country. He later sent annual allowances to two family members (mentioned also in his will) and gave generously to Friends' causes if warranted.

Dalton's instruments were homemade so that his measurements were never too accurate, although he was a careful experimenter. His demonstration lectures at the Royal Institution (1803, 1810) were not successful. He lectured also at the University of Edinburgh. His main forte, however, was his natural ingenuity. His continuing interest in the atmosphere led in 1803 to his own investigation of the solubility of gases in water, complementing the studies of William Henry (1775-1836). Two years later he showed that each gas in a
mixture behaves independently, that is, each with its own (partial) pressure.

Dalton's primary contribution, however, was the resurrection of Democritus's (496-438 B.C.) atomic theory, which assumed matter to be made up of atoms having the same substance, size, form-and possibly weight. He assigned a distinctive weight to each atom. Using Joseph Louis Proust's (1754-1826) law of definite proportions (1799) for any chemical compound, he was able to estimate relative atomic weights on the basis of one for hydrogen. Water, for example, would be 6.66 with I part hydrogen and I part oxygen (5.66).
In this way he was able to produce the first table of approximate "atomic weights." In the case where two elements combine to form more than one compound, he showed that simple ratios of atoms would be involved-a theoretical deduction of the Law of Multiple Proportions, later verified experimentally. Dalton's ideas were not accepted at once by everyone, for instance, Humphry Davy (1778-1829). His own scientific work deteriorated with age.

Dalton had religious convictions; he had reverence for God and respect for the Scriptures. He was not, however, interested in theological controversies. He attended Quaker meetings twice every Sunday, as well as the Quarterly ones. He would not generally accept Sunday invitations for dinner. He did make one liturgical suggestion, the limited use of music on occasion at meetings. He drank water only; he did smoke a pipe.

This is the nineteenth in a series on profiles of scientists with religious leanings.