Leeuwenhoek microscope

The single double-convex lens is fixed in the aperture towards the top. In contrast to modern microscopes in which the specimen is fixed and the lens are moved, Leeuwenhoek's specimens is mounted on the pin in front of the lens. It is raised and lowered with the large key on the screw mechanism, and is focused by moving it closer or further from the lens with the round knob. Surviving lens are capable of 275 X magnification.