This week's object is a calotype negative from the Science Museum Group Collections depicting the Round Tower at Windsor Castle. It was taken by William Henry Fox Talbot, one of the pioneers of British photography in the 1840s, and is labelled '41' on the reverse.
See this item on the Science Museum Group Website.
Connection to last week's item: Robert Boyle had expanded upon experiments first done in thirteenth century Albertus Magnus (c. 1200-1280) that had noted that silver nitrate, when exposed to light, darkens. Boyle examined the phenomenon more carefully and reported his findings in his 1663 publication Experiments and Considerations Touching Colours. Calotype negatives utilise this property of silver nitrate to record the image.