Emma Hardinge Britten with a spirit

The woman in the photograph is Emma Hardinge Britten (1823–99), an English leader in the early spiritualist movement. She visited the US and was invited by the famous spiritualist, Horace Day to host seances. She went on to became a 'trance lecturer' and delivered speeches across the country.

The photographer is William Mumler (1832-1884). Mumler was an American jeweller who left his job to become a spirit photographer. His first spirit photograph was a self-portrait which apparently show his deceased cousin.

His business boomed at a time when large numbers of people had lost relatives during the American Civil War (1861-1865). His most famous photograph was of Mary Todd Lincoln with the ghost of her husband Abraham Lincoln. 

Eventually Mumler was taken to court for fraud, where the famous showman PT Barnum testified against him. While not found guilty, his career as a spirit photographer was over.