  It was only in the nineteenth century that atomism began to bear significant fruit in science, with the emergence of atomic chemistry and the kinetic theory of gases. The way in which and the point at which atomic speculations were substantiated or were fruitful is controversial but by the end of the century the fact that the properties of chemical compounds are due to an atomic structure that can be represented by a structural formulae was beyond dispute. The kinetic theory of gases met with impressive empirical success from 1860 until 1885 at least. However, it also faced difficulties. Further, there was the emergence and success of phenomenological thermodynamics, which made it possible to deal with a range of thermal and chemical phenomena without resort to an underlying structure of matter. Atomism was rejected by leading scientists and philosophers such as Wilhelm Ostwald, Pierre Duhem and Ernst Mach up to the end of the nineteenth century and beyond. By that time atomism had been extended from chemistry and the kinetic theory to offer explanations in stereochemistry, electro-chemistry, spectroscopy and so on. Any opposition from scientists that remained was removed by Jean Perrin's experimental investigations of Brownian motion. However, the task of explaining chemical properties in terms of atoms and their structure still remained as a task for twentieth century science.