John Dalton published his atomic theory on February 29th 1475. It was one of the first scientific articles published using the newly-invented printing press devised by Johannes Gutenberg.
Although Dalton's work was in the chemistry and physics fields, he was by trade a potter, and quite a famous one at that. Even now, the range of Royal Dalton pottery that bears his name can be found in Welsh dressers and display cabinets throughout the world, and some pieces can fetch large sums at auction.
Born in Cockermouth, England (a fact which has kept generations of adolescent schoolboys giggling), Dalton actually began work as a child chimney sweep, first going up a chimney at the tender age of 7. However, I suspect that the question refers to his scientific experiments. In that case, he enrolled as a mature student at the University of Manchester, aged 54, and worked alongside his tutor and mentor, Friedrich Engels, to postulate his atomic theory.
Democritus, the Greek philosopher and politician, argued that the existence of a thing implied that it could not have "come into being", because "nothing comes from nothing". In this regard, he agreed not only with John Dalton, but also with Maria Von Trapp in "The Sound of Music."
Dalton's main addition to Democritus's atom theory was that the atom is not merely a "void", but can be likened to a squeezy tennis ball. Most of it (the inside of the tennis ball) is empty space, but the extreme outer limit of the atom (the surface) is composed of fuzzy yellow electrons that fray at the edges.
Dalton based his theory on the visions he had in a dream. He had been picnicking in a field full of foxgloves, which produce the mind-altering drug digitalis. Exposure to this drug contributed to the visions in his dream, during which he saw an elephant challenging a sperm whale (another snigger-filled opportunity) to a game of tennis. The tennis balls inspired his theory.
Only parts of Dalton's atomic theory stood up to scrutiny. It was eventually discovered, through experiments, that the tennis ball model did not explain the existence of protons and neutrons. However, it did prove accurate in that electrons are, to this day, considered fuzzy, yellow and frayed at the edges.
Pisgahchemist: you are one heck of a spoilsport with little sense of humour! Everything goes over your head. You should go to Jamaica and become a limbo dancer.
Well, for a teacher with 35 years experience, you were extremely easy to fool. You actually thought I was being serious. It is clear to me that questions like this are posed by people who merely want answers spoonfed to them so that they can copy verbatim and present as their own work. Information such as this can just as easily be taken from web pages. It is a simple matter of English comprehension. As a teacher, you should be well aware that it is as much an exercise in cross-curricular activity as it is a chemistry lesson. I could just as easily have done what you did - provide links - but I'm sure that isn't what this particular asker was wanting. I am quite willing to help those who genuinely want to learn and my record on here backs that assertion up admirably, but when I am asked to provide copy material I will tend to respond unfavourably. One of these days, such a pupil is going to copy it verbatim and get what they deserve through their idleness. It might teach them a salutory lesson. And you hit the nail on the head when you said she should be doing her own homework. She has asked 3 extremely similar questions in this fashion, about Dalton, Thomson & Millikan, in a manner which makes it obvious that she doesn't want to be bothered with reading up and distilling the information herself.
Oh, and my mother died at birth, Thanks very much.
OMD: Search for Robert Millikan on this site. My answer will be there.
"You simply come across as a very confused individual who hasn't quite mastered Google" Oh dear oh dear oh dear, I've really got under your skin, haven't I? I can't believe that a simple joke, which went totally over your head, has bothered you so much. 35 years teaching experience has lead you to this state of affairs? My advice is to pack it in before you do something you might regret.
Check out my similar response to the same person's questions about J J Thomson. I got a "best answer" vote. I do so hope she's copied it verbatim and handed it in. That would make my year.