Robert Hooke's drawing of his own compound microscope in Micrographia (1665). The illuminator (left) consisted of an oil lamp with a spherical flask acting as a condenser (G). The specimen was mounted on a pin (M). Focus was obtained by racking the whole microscope up & down using the screw (G), which was held by a clamp (D). Hooke (1635-1703) was the curator of experiments at the Royal Society of London. Reference: MICROCOSMOS, page 186, Technical Appendix.