Brewster, David, Sir, 1781-1868, Smith, James Alexander · London, Chatto · leaf 198
ht and shadow. Hence the illusion depends on the accuracy and extent of our knowledge on this subject ; and while some persons are under its influence, others are entirely insensible to it. When the seat or hollow cavity is not polished, but ground, and the surface round it of uniform colour and… … of a hollow is always on the side next the light, and the shadow of a protuberance on the side opposite to the light ; but if the object is the raised impression of a seal upon wax, I have found that when inverted it still seemed raised to the three youngest of six persons, while the three eldest…
Magic · Scientific recreations
Internet Archive · Gerstein - University of Toronto · Public domain (published before 1931). Free to use for anything.
