Glass plate with etched list of the semi class in Natural Philosophy List of semi class in Natural Philosophy, on the occasion of a presentation to William Knight, 'etched with fluoric acid gas' with a note and letter from Miss Margaret Knight, 1905. 'The names of those of the students of a class at Marischal College Aberdeen, under Mr William Knight to whom they presented a gold snuff-box also in my keeping'. The list is etched on a small glass plate. 1810 - 1811