Images Dated 20th November 2003

DNA swab

DNA swab and police evidence form. The sterile cotton bud is used for collecting cells from the lining of the mouth to be analysed by DNA fingerprinting. DNA profiles of suspects in a crime investigation can be compared with DNA obtained from the crime scene, for example from hair, blood or other body fluids. A person's DNA fingerprint is unique to them, therefore this technique can both eliminate people from an enquiry and confirm the identity of the offender

© Tek Image/Science Photo Library

Egypt. Satellite pyramids of the Great Pyramid of Khufu or C

Egypt. Satellite pyramids of the Great Pyramid of Khufu or Cheops, known as The Pyramids of Queens. From right to left: pyramid G 1-a, attributed to Hetepheres I (mother of Cheops) pyramid G 1-b attributed to Meritites I, and the Pyramid G1-c attributed to Henutsen (mother of Khafre and Khufu's third wife) . 4th dynasty. 26th century B.C. Old Kingdom. Giza

© Thaliastock / Mary Evans

Clay soil

Clay soil. Soils with a high proportion of clay typically stick together and are greyish in colour. Clay particles are the smallest particle of the different soil types, giving the soil a smooth feel when rubbed between the fingers. Such small particle sizes means that water cannot drain easily through clay soils, resulting in land with poor drainage. For this reason, clays are known as heavy soils, because they are heavy to work. Clay soils are usually very fertile, however

© SHEILA TERRY/SCIENCE PHOTO LIBRARY