kept at Stourhead. Cunnington made meticulous recordings of mainly neolithic and Bronze Age barrows, and the terms he used to categorise and describe them are still used by archaeologists today. The first reference to the use of a trowel on an archaeological site was made in a letter from Cunnington to Hoare in 1808, which describes John Parker using one in the excavation of Bush Barrow. One of the major achievements of 19th century archaeology was the development of stratigraphy. The idea of overlapping strata tracing back to successive periods was borrowed from the new geological and palaeontological work of scholars like William Smith, James Hutton and Charles Lyell. The application of stratigraphy to archaeology first took place with the excavations of prehistorical and Bronze Age sites. In the third and fourth decade of the 19th century, archaeologists like Jacques Boucher de Perthes and Christian Jürgensen Thomsen began to put the artifacts they had found in chronological order. Another important development was the idea of deep time. Before this, people had the notion that the earth was quite young. James Ussher used the Old Testament and calculated that the origins of the world were on 23 October 4004 BC (a Sunday). Later Jacques Boucher de Perthes (1788–1868) established a much deeper sense of time in Antiquités celtiques et antédiluviennes (1847). Professionalisation As late as the mid-19th century, archaeology was still regarded as an amateur pastime by scholars. Britain's large colonial empire provided a great opportunity for such 'amateurs' to unearth and study the antiquities of many other cultures. A major figure in the development of archaeology into a rigorous science was the army officer and ethnologist, Augustus Pitt Rivers. In 1880, he began excavations on lands that came to him in inheritance and which contained a wealth of archaeological material from the Roman and Saxon periods. He excavated these over seventeen seasons, beginning in the mid-1880s and ending with his death. His approach was highly methodical by the standards of the time, and he is widely regarded as the first scientific archaeologist. Influenced by the evolutionary writings of Charles Darwin and Herbert Spencer, he arranged the artefacts typologically and (within types) chronologically. This style of arrangement, designed to highlight the evolutionary trends in human artefacts, was a revolutionary innovation in museum design, and was of enormous significance for the accurate dating of the objects. His most important methodological innovation was