An arrangement of selected diatoms (marine collections) from Alexandria (presumably Egypt). Mountant has gone orange. Prepared by William Allot Firth. 20x Nikon Plan Apo NA 0.65 objective. Olympus Aplanat Achromat condenser, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 43 images stacked in Zerene (Pmax).