Ghosts everywhere, and of any colour," was the promise of Spectropia, a book of "surprising spectral illusions" published in 1863. Optical illusions were among the twenty vol. 084 topics, chosen by their readers, which were concerned with science, technology, and medicine, including the societal implications of decision making in these fields: (The Equality of Inertial and Gravitational Mass; The Machine That Thinks; Rocks For Homes; Ottawa Illinois Radiation Area; Florence Nightingale to ...