Hippolyte Baraduc (1850–1909) was a French physician and parapsychologist. He is most notable for his claim that a misty form leaves the human body at the moment of death which he believed was evidence for the soul.
In France, Dr Hippolyte Baraduc and Louis Darget[did experiments in 1895 on thought photography and he produced colour photos on glass, mainly showing human fingerprints with aura forms.] attempted to photograph thoughts or psychic energy (‘the light of the soul’) simply by placing foreheads or fingers on a photographic plate. Despite refutations by experts, who argued that the results claimed by the ‘effluvists’ were merely technical accidents, these experiments continued throughout the 20th century.
In one experiment, Hippolyte-Ferdinand Baraduc fastened a pigeon to a board and strapped a photographic plate to its chest. He then cut the pigeon's throat, "the picture of its death agony taking the form of curling eddies' on the plate. In a paper read before the Society of Psychic Sciences in Paris, Baraduc claimed to have photographed the human soul or "vital force. " He placed a photographic plate on the body of a man in a totally dark room which "received an impression from the vital forces three hours after death. "[The British Journal of Photography, 26 June 1896, p. 412; The Photographic Review, Vol. 2. , no. 1, January 1897, p. 19.]
Baraduc also photographed both his son and his wife, one four minutes after death, the other 24 hours after death. The "vital force" was pictured stretching from the bodies in a fluid stream which hit the ceiling of the room and arced down again.
Biometer - an instrument designed by Hippolyte Baraduc and claimed to measure a vital force which is emitted by the human body. The instrument consists of a bell glass, from the inside of which is suspended a copper needle by a fine silken thread. The glass stands on a wooden support, below which is a coil of copper wire, which, however, is not connected with any battery or other apparatus, and merely serves to condense the current. Below the needle, inside the glass, there is a circular card divided into degrees to mark the action of the needle. Two of these instruments are placed side by side, but in no way connected, and the experimenter then holds out the fingers of both hands to within about an inch of the glasses. According to the theory, the current enters at the left hand, circulates through the body, and passes out at the right hand, that is to say, there is an indrawing at the left and a giving-out at the right, thus agreeing with Reichenbach's experiments on the polarity of the human body.
"The Human Soul: its movements, its lights and the iconography of the fluidic invisible" by Hippolyte Baraduc
One of the most convincing proofs I have seen is that afforded by the "biometre," a little instrument invented by an eminent French scientist, the late Dr. Hippolyte Baraduc, which shows the action of what he calls the "vital current." The Edinburgh Lectures on Mental Science, by Thomas Troward, 
Ernest William Hornung ( 1866 – 1921), known professionally as E. W. Hornung (nickname Willie), was a poet and English author, most famous for writing the A. J. Raffles series of novels about a gentleman thief in late 19th century London.
In 1911 a photographic journalist declared that "Photography is becoming too sensational for the liking of quiet minds. ”[ The Amateur Photographer, 1 May 1911, p. 444.] The event which prompted this remark was the publication of a strange novel, "The latest clever exploit in hair-raising fiction," by a popular turn-of-the-century author, E. W. Hornung. Although Hornung wrote over 30 books, his name has been largely forgotten in the annals of popular fiction. This is understandable. His novels were urbane, witty, well-crafted but not very profound.
The Camera Fiend, written in 1911, is a strange tale about a crazy photographer/scientist and a young snapshot enthusiast whom he befriends.
The hero, an asthmatic youth named Pocket, is found sleepwalking with a pistol in his hand while nearby is the body of a tramp, a "dilapidated creature lying prone," who had been shot moments earlier. It looks bad for young Pocket.
He is approached by an odd looking man, Dr. Otto Baumgartner, who had attended various universities studying psychology and theology until becoming obsessed with proving the existence of the human soul.
Baumgartner disarms and wakes up young Pocket who later notices a stereoscopic camera beneath the Doctor's cloak. They discover a mutual interest in photography and, back at Baumgartner’s home, they discuss the pleasures of the camera. Quickly, however, it is established that they have different aims. Baumgartner is a psychic photographer obsessed with capturing the human soul in a picture
It is possiblre that experimental attempts at photographing the human soul at the moment of death, such as those by Baraduc during the 1890s, were prime sources for E. W. Hornung and his plot of The Camera Fiend.
 Baron Karl von Reichenbach (1788-1869). Nineteenth-century German chemist, expert on meteorites, and discoverer of kerosene, parrafin, and creosote. He also spent over two decades experimenting with the mysterious force which he named "od" (also known as odic force or odyle in various translations). This claimed force, which has its intellectual roots in Mesmerism, had particular relevance to concepts of the human aura.