Written for Brought to Light by: Joe Mueller. Research Group: Erin Lukas, Richard Cornhill, Anna Jackowiak, Joe Mueller.

Maker: E. Esdaile & Sons, Sydney.

This E. Esdaile & Sons "Sirius" Mirror Stereoscope, made in the 1940s and acquired by the University of Adelaide Department of Earth Sciences in 1956, was likely used in mapping the northern outback regions of South Australia during the 1960s and 1970s.

E. Esdaile & Sons began manufacturing scientific and optometry equipment in 1891. This particular device was made in the 1940s most likely during World War II, and used for preparing geological field maps. At some point in its life, it was used by the University of Sydney before it was acquired by Professor Eric Rudd in 1956. From 1949 Professor Rudd held the Chair of Economic and Mining Geology at the University of Adelaide until 1970, and was a student of Professors Sir Douglas Mawson (Geology) and Sir Kerr Grant (Physics) and later a graduate of Harvard University. He has a scholarship in his name at the University of Adelaide. The stereoscope may have been used at the time in a process involving three steps:1. An aircraft with a camera flies over the area to be surveyed, while the camera takes consecutive photographs overlapping each other by two-thirds. 2. Geologists in the field identify, locate and trace out geological features on the aerial photographs using the stereoscope. 3. Back in the lab, the stereoscope is used to amalgamate all of the field observations and, using the 3D effect, combined with the field measurements and observations, produce geological maps.

In general, a stereoscope is an optical device used to view two, two-dimensional images as one creating one three-dimensional image (a stereogram). The '3D' effect created by the stereoscope was useful in visualising landscape features including elevations and contours in a given region - in this case the two-dimensional images are pairs of partly overlapping aerial photographs. Combined with field measurements, these devices would assist in making highly accurate topographical maps and also formed an important aid to geological mapping in the field.