The overlapping field of interest of geology and chemistry varied in extent and degree throughout the nineteenth century. In the ‘heroic’ days of geology, at the beginning of the century, there was a close relationship, with chemists of note displaying not only an interest but a considerable expertise in geology. Geologists who were interested in crystalline rocks, caught up in the Neptunist/Vulcanist debate, dealt with chemical aspects of their subject as a matter of course. This pattern of work persisted throughout the century on the continent of Europe, but in Britain, for a wide variety of reasons, geologists used chemical data and techniques very little, and petrology in that country suffered accordingly. However, in the second half of the century, as advances were made in the technology used by geology, especially with the polarising microscope, in the education of professional geologists and the dissemination of knowledge from Europe and the Americas, the situation improved, so much so that, by the last two decades of the century British petrology had absorbed chemical geology into its armory of skills and knowledge and was on a par with geology from elsewhere in the world.
