This collection of 3,465 glass positive slides were acquired from the Roslin Institute in November 2009 as part of a larger accession of material. The slides, which range in date from the 1870s to the 1930s, cover a wide range of subjects; photographs of indigenous peoples from around the world, international travel scenes, personal portraits (frequently of figures connected with the natural/veterinary/agricultural sciences), images and portraits of domestic animals (chiefly sheep, poultry, cows and pigs), illustrations and extracts from books, articles and newspapers. The majority of the slides are black and white, although some are hand-coloured or tinted. Many of the slides were produced by T.J. Walls, an optician on Forrest Road, Edinburgh.

It is thought that at least a proportion of the collection was created or collected by James Cossar Ewart as well as Robert Wallace, in their capacities as professors of, respectively, Natural History and Agriculture at the University of Edinburgh, and were probably used for teaching and illustrative purposes. Both Ewart and Wallace appear (separately) in the slides, as do colleagues and other persons known to both or either of the men. While some of the slides appear to be directly associated with Ewart and/or Wallace, it is supposed that a proportion of the collection may have been sent to them by colleagues from around the world. It is not known how the collection ultimately came to reside at the Roslin Institute.