X-Ray Photographs as Pictures

that refraction by a lens is not indispensable to the formation of a photographic image. The effective range of fluorescent and actinic X-rays is limited to two or three feet, and for this distance from a camera a "pinhole" in a metal disc does quite as well in ordinary photography as any lens or combination of lenses, so far as pictorial effect and clearness are concerned, provided the exposure is sufficiently prolonged. The focus of a "pinhole" camera is the crossing station for reflected rays; the centre of the anti-cathodal plate of the