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.New York: OxfordUniversity Press, 1987.Brief biographies of 12 high-profile sci-entists and the development of science as influenced by socialforces.Colorful illustrations.Poole, Lynn, and Gray Poole.Scientists Who Changed the World.NewYork: Dodd, Mead, and Company, 1963.Easy-to-read profiles ofthe scientists who made a dozen revolutionary discoveries.Saari, Peggy, and Stephen Allison, eds.The Lives and Works of 150Scientists.Vol.2.Detroit, Mich.: U*X*L, 1996.Alphabeticallyarranged introductions to the contributions of scientists from avariety of fields.Intended for middle school students. 3John Dalton(1766 1844)John Dalton formulated the chemicalatomic theory.(Science PhotoLibrary/Photo Researchers, Inc.)The Chemical Atomic TheoryThe Greek philosopher Democritus was the first to use the wordatom, meaning indivisible, to describe the smallest unit of mat-ter.Today an atom is defined as the smallest component of an ele-ment that retains the chemical properties of that element.Atomscombine to form compounds.The smallest physical unit of a com-pound is a molecule.These concepts are introduced at the begin-ning of chemistry courses because all of chemistry is defined in35 36 Chemistrythese terms.When a Quaker teacher named John Dalton proposedthe atomic theory at the beginning of the 19th century, he shedlight on many of the previously unexplained chemical phenomenaand laid the foundation of modern chemistry.While he did notinvent the idea of the atom, he was the first to define it in terms ofweight and to provide chemical evidence for its existence.Dalton isalso credited with proposing the law of partial pressures and the lawof multiple proportions.A Quaker UpbringingJohn Dalton was born on September 5 or 6 (records disagree),1766, to Joseph and Deborah Greenup Dalton in Eaglesfield, nearCockermouth, England.His father was a cloth weaver and a mem-ber of the Society of Friends, also known as Quakers.Quakersbelieved man had control over his own salvation, in pacifism, plaindress and speech, and equality of men and women in education andin the ministry.Quaker religious beliefs made an impact on John supbringing and adult lifestyle.John had an older brother namedJonathan and a younger sister named Mary.John and Jonathan often helped their father weave and work inthe fields, but they also attended the local Quaker school wherethey learned English, arithmetic, the Bible, and a little geographyand history.John was a good student and received additional tutor-ing in science from a wealthy neighbor named Elihu Robinson, whoallowed John to use his library.As a young adult, John displayed an extraordinary thirst forknowledge.When he was 13 years old, John copied manually anentire issue of Ladies Diary, a popular magazine that containedmathematical puzzles and challenges.Over the next two decades hecontributed to this magazine 60 times, including his first publishedpiece of writing in 1787, an answer to an algebraic problem.Because there was a shortage of teachers, John took over the localschool at the youthful age of 12 when the former schoolmasterretired.John, however, was unable to control some of the olderrowdy students who were perhaps a bit resistant to taking direction John Dalton 37from a younger boy.Thus, after one year John simply workedaround town doing odd jobs.A Natural PhilosopherAt the age of 15, John s brother asked him to come to Kendal, 45miles (72 km) away, to tutor at a boarding school that one of theircousins owned.After a few years, their cousin left the school, andJohn and Jonathan served as joint principals.The school owned asmall but respectable collection of scientific literature and appara-tuses of which John took advantage.He taught there for a total of12 years on a variety of subjects.During these years, Dalton spent his free time furthering his ownknowledge in mathematics and science under the tutelage of aphilosopher named John Gough
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