An index to the manuscript notebook collection was set up in the 1990's. The notebooks themselves contain detailed information gathered by BGS geologists (or other recognised geologists) from various sources as part of the mapping of Great Britain since the 1840s. Examples include observations linked directly to field slips, borehole logs, sections and drawings. All the notebooks held by National Geological Records Centre (NGRC) are indexed but other notebooks held in the Library may not be included. The index is to the notebooks and is not a detailed index of the information in the notebook. Detailed information from coalfield areas is held in the Happs Hall Index. For the basic field mapping work notebooks have now been replaced by field record sheets.