Since its inception in 1948, various Harvard departments and private benefactors have added material to the original nucleus of the Collection of Historical Scientific Instruments, which now contains over 20,000 objects dating from about 1400 to the present. A broad range of scientific disciplines are represented, including astronomy, navigation, horology, surveying, geology, calculating, physics, biology, medicine, psychology, electricity, and communication. Many of the documents detailing the purchase and use of the instruments have been preserved, and are available for research in the Collection's adjunct library.