John Dalton changed the course of the human understanding of physical makeup with his atomic theory of matter, which states that minute, indestructible particles, called atoms, comprise all elements. Dalton arrived at this theory by considering the properties of gases. Dalton’s law, or the law of partial pressures, states that the total pressure of mixed gases amounts to the sum of the pressure of each individual gas. Dalton also contributed to the understanding of the aurora borealis, the origin of the trade winds, the barometer, the thermometer, the hygrometer, the dew point, rainfall, and cloud formation. His limited educational background freed him from academic prejudice, and he carefully guarded his freedom of thought against undue influence by accepted theories. Dalton trusted his own observations and experience to guide his scientific research.
Best known for his atomic theory of matter, John Dalton also contributed to the understanding of the aurora borealis, the barometer, the thermometer, and other scientific principles.
Dalton was born on September 6, 1766, in Eaglesfield, in Cumberland, England. His parents were Mary Greenup Dalton and Joseph Dal-ton, a Quaker weaver. The younger Dalton inherited his family’s modest farm in 1834 when his older brother, Jonathan, died. Dalton devoted himself exclusively to his work and his religion, never marrying.
By the age of 12 Dalton had acquired enough education to commence teaching in Cumberland’s Quaker School. At the age of 14 he moved to Kendal, where he taught with his brother at the Quaker School for the next 12 years. In 1793 he moved to Manchester, where he taught mathematics and natural philosophy at the New College in Manchester, established by the Presbyterians as an alternative to Cambridge and Oxford, which required oaths to the Church of England.
Dalton published his first book, Meterological Observations and Essays, in 1793, based on his journal of meteorological observations started in 1787. The next year he published Extraordinary Facts Relating to the Vision of Colours, an issue of personal concern as he was color-blind. In 1800 the Manchester Literary and Philosophical Society appointed Dalton as secretary, and he read most of his papers there throughout his lifetime.
The society appointed him president in 1817, a position he maintained until his death.
Dalton presented four important papers to the Society in 1801. "On the Constitution of Mixed Gases" expounded his law of partial pressures; "On the Force of Steam" discussed the dew point and represented the founding of exact hygrometry; "On Evaporation" proposed that the quantity of water evaporated was proportional to the vapor pressure; and "On the Expansion of Gases by Heat" stated that all heated gases expand equally. This last principle is known as Charles’s Law, as Jacques Charles discovered the effect in 1787, though Dalton published his statement first.
In 1802 Dalton presented his paper "On the Absorption of Gases by Water," to which he appended the first table of atomic weights. In a December 1803 lecture to the Royal Institution, Dalton explicated for the first time his atomic theory, which held that all atoms of a particular element are alike, having the same atomic weight. Dalton published this theory in his 1808 text, A New System of Chemical Philosophy, which he revised in 1810 and 1827.
Dalton received a Gold Medal from the Royal Society in 1826, but it was not until after his death that Stanislao Cannizzaro, in 1858, reasserted Amedeo Avogadro’s theories from a half-century earlier that confirmed Dalton’s atomic theory undisputedly. Even without this final confirmation, Dalton’s influence was immense, as evidenced by the 40,000 people who attended his Manchester funeral after his death on July 27, 1844.
