Although incomplete, even fragmentary, Rochas' correspondence touches on a wide range of his interests in psychic research between about 1885 and 1910, including some scarce published articles from the psychic and popular press and several pamphlets on topics of interest. In most cases, correspondents are represented by only one or two letters lacking Rochas' replies. Pieced together, however, these provide an outline of his major research interests and of his connections to other significant psychic researchers in France, Germany, Italy, and elsewhere, such as Albert Philibert Franz Schrenk-Notzing, Willy Reichel, Bogdan Hasdeu-Istrati, and Alexander Aksakoff. Rochas also maintained correspondence with a number of artists and writers, including James Tissot, Alphonse Mucha (although there are no letters from Mucha present).

Concerned with documenting Spiritualist séances and exploring the underlying basis of psychic phenomena, Rochas received a regular influx of letters from other investigators describing their experiences and experiments. His colleagues kept Rochas informed of the activities of the mediums Eusapia Paladino and Charles Bailey, of research conducted in Italy, France, Germany, Australia, and the United States (see A. Van der Naillen), and there are excellent accounts of experiences with somewhat lesser known operators such as Mme Escalier (see Fernand Boudron), Mme. Adam (see the fascinating 10 page account of psychic occurrences at a seance by Lydie Rostoptchine), Mme Corner, and the Theosophist Mme Blavatsky. More unusual is the letter of M. Lagelouse, who writes that she has been persecuted for eight years, and who sends the names of friends near the moon to vouch for her.

The Orientalism that marked Spiritualism and Spiritism in the latter decades of the 19th century can be seen throughout the Rochas Papers, not only in the correspondence with or about Theosophists. There are excellent letters on reincarnation from G. Berger, C. Cania, and Annie Besant (the Theosophist), and there is a hint of it in his interest in the possibility of the exmigration of the living soul (see Alexandre Goupil's Cas de vision fantomale and Cas de vision fantomale d'un vivant) and his work on Ecstasy. There is a considerable quantity of material on the sensitive Maria Mayo (Lina) -- Schrenck-Notzing's subject -- and on the physiological effect of music (see e.g. Frandoni Lacombe, Atelier Mucha). Among the miscellaneous items of note are a wonderful letter by the Danish military engineer E. Christmas-Dirckinck-Holmfeld on spirit photography, and a small number of letters from otherwise unidentified persons (e.g. Berthe Dole) who wrote to share their personal psychic experiences.

Rochas evidently placed a great importance on photography as a means of documenting elusive spiritual and psychic phenomena, and the Rochas Papers includes 69 photographs depicting spirits, psychic forces, séances, mediums, and "sensitives" taken between ca.1875 and 1900. Spirit photographs seem to have been of particular interest, and his papers include two interesting images taken by the famed (and debunked) Parisian Eugène Buguet, two prints of the spirit Bien Boa (a "Brahmin" materialized by the medium Marthe Béraud), and several other images, the most intriguing of which was taken in Elizabeth, N.J., of Elena de Obarrio, in which her guardian spirit and the spirit of her sleeping (and very much alive) brother also appear. This image was taken by, or with the assistance of the Cuban medium J. R. Simoni. Rochas also kept photographs of a séance conducted by Guy de Fontenay with Eusapia Paladino at Montfor l'Amaury, July 1897, including two cabinet cards of a séance in progress and a psychically-produced image of Paladino's face.

Less common are a suite of photographs that demonstrate the reality of psychic forces. A fine carte de visite of Gustave Flaschoen taken by the British photographer Brittlebank displays the "force psychique sortant de ses mains," while three cartes provide a dramatic illustration of psychic force being generated by a circle held by the medium John Beattie in Bristol, England. The photographs Rochas collected of "sensitives" reflect his interests in the physical effects of art and music and his interest in the experience of religious or spiritual ecstasy.

Other images document psychic forces in less concrete ways. The collection includes a series of 11 images associated with the Romanian psychic investigator Bogdan Hasdeu-Istrati (see also his correspondence), 11 "doubles" of Mme. Lambert, sent to Rochas by the editor G. Delanne, and the image by Mme de Valpinson are generally difficult to interpret visually, while in those of Paolo Visani Scozzi (apparently mounted for public display) one can see dim faces arising from amorphous psychic clouds. Rochas was also not coincidentally interested in x-radiography, acquiring a very early (March 1897) x-radiograph of a hand, apparently kept as demonstration that photography could reveal structures otherwise hidden to the eye. Equally interesting are several images taken by the photographer Nadar, including five boudoir cards of Rochas himself with an astral body "obtenu par trucage."