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 to the influence of women, for a warm friendship existed between him and Miss Nancy Wilson. The lady died young, but he always cherished her memory with affection. Another valued friend of Dalton's was Mademoiselle Clementine Cuvier, the daughter of the celebrated naturalist.

Concerning Dalton's atomic theory, it may be stated that he introduced the idea of weights—his theory is essentially one of weight—the relative weights of the different atoms. The first public notice of the atomic theory is contained in his paper, "An Experimental Inquiry into the Proportion of the Several Gases contained in the Atmosphere." He found that oxygen has the power of combining in two different proportions with nitric oxide, forming two distinct bodies, and that the quantities by weight of oxygen which combine are in the simple ratio of one to two. No intermediate compound could be obtained. It was this fact that led to the atomic theory, and the law of multiple proportions. "It is to Dalton—who made his living by giving private lessons at half a crown each—that we owe this knowledge which has made the fortunes of thousands, because he first told us the laws which govern chemical action."

Dalton's atomic theory is, however, somewhat different from the one of to-day. In his day the smallest particle (elementary or compound) was an atom, whereas now compound bodies are composed of atoms of the elements