The Hudson Transparencies Created by Hudson to illustrate his lectures, the 'Hudson transparencies' are a collection of 58 large framed paintings on paper screens. These visual teaching aids illustrate microscopic organisms and were designed to be viewed backlit in a darkened room. Each screen is in a wooden frame, approximately 96cm high by 76cm wide. The paintings are on translucent white and coloured paper, with perforations to create highlights. Thick brown paper forms a mask so that only the image is seen, when lit from behind. It is thought some of these were created in the mid 1880's or later. Hudson's way of working is described in a handout produced by the Biology Department, University of Exeter: 'His method was to rough out the portrait of his animal in chalk on a sheet of thick brown paper and then to cut out large areas over which he pasted a thin white paper upon which he painted the appropriate parts. All the more delicate lining was however done by a series of pinpricks. The final results when illuminated from behind are not only extremely accurate portraits of his subjects but quite thrillingly beautiful' See Dr Robin Wootton's list for further details: http://devonassoc.org.uk/the-hudson-transparencies 'Open day' handout and 1981 'Open day' handout on Collection file 19th century