A skiagram (or skiagraphy), aka "shadow photograph" was an early term for x-ray photography. Here is a demonstration on the method for obtaining a skiagram, 1896. From: "Archives of Clinical Skiagraphy," vol.1. Historical Medical Library of The College of Physicians of Philadelphia.
20 mars 1896. - Balle masquée depuis deux ans. - 45 minutes de pose. Barthélemy, Toussaint . - [Collection de 65 photoélectrographies, premières radiographies obtenues en France]. Paris, 1896. BIU Santé -