In this 100 year old book the mechanics of spirit photography are explained by apparent spirits communicating through mediums. It has to do with ether and semi-materialization apparently. However, the presence of a medium before the taking of the photograph is essential, reportedly. In addition, the medium should be morally and physically healthy and able to maintain a passive mental state. Anxiety is reportedly a great hindrance. That way, the subconscious thought forms are liberated. There's a photo of Alfred Russel Wallace and his deceased mother. Wallace states, "The facts were too many for me." Photos of people's doubles were apparently also possible, such as the photo taken of medium Stainton Moses and his double. Mr. Coates includes a photo of himself and his dead wife. Thought photography is discussed towards the end of the book, which apparently dates from 1876. Images of objects enter and fix themselves in our brains through the retina, and then they can leave our brains by the same route, reportedly. Coates includes a letter from a correspondent who reportedly received evidence that there is a large band of workers in the spirit world who are "helping to convince the Western World that there are things and beings which cannot be cognised by ordinary sense faculty." A good book to generate conversation about