Under 55 is classed information about all the earth sciences: geophysics, seismology, terrestrial thermodynamics, electricity and magnetism, geochemistry, geobiology, prospecting; physical and dynamical geology, including vulcanology, tectonics, glaciology, geomorphology and oceanography; meteorology, stratigraphy, palaeogeography; petrology and petrography; economic geology; and hydrology. Though economic geology is essentially the study of useful deposits, class 55 generally covers the pure aspects of all these subjects; the related applied sciences are classed mainly in the divisions of class 6.