"Feathers of Humming Bird, Brittle Star Fish, Fossil Tooth of Shark"

These slides have cover slips of thin glass, which was very expensive and difficult to produce before the 1840s—early mounters more often used sheets of mica, which was far from transparent. The use of Canada balsam sap (which preserves structures and eliminates air and water from samples) as a mounting medium also vastly improved the view.

From a SEED Magazine slideshow of Victorian microscope slides. Those shown above are from the collection of Howard Lynk, who has many more; the arranged slides of diatoms and spicules are quite lovely.