An archangel revealing the physical nature of the universe to a group of natural philosophers and mathematicians. Etching by… https://www.rawpixel.com/image/13981037/image-paper-cartoon-personFree Image from public domain licenseGeorge Adams demonstrates his electrotherapy machine to a woman and her daughter. Line engraving by J. Lodge, 1799, after T.… https://www.rawpixel.com/image/13990992/image-cartoon-person-artFree Image from public domain license