The Filter Attenuation Measurement System was designed by J.H. McCrary. It is, as its name implies, primarily intended to measure the attenuation of an x-ray beam by various substances. However, it can also be a very useful instrument for qualitative as well as quantitative analysis through the use of absorption edge spectrometry. The essential components of the system are depicted. The brehmstrahlung originating in a tungsten target x-ray tube is collimated and the desired energy picked out by varying the angle that the primary beam makes with the (200) set of planes in a LiF crystal. The reflected beam, which is monochromatic, passes through two collimators before being detected by a NaI counter. The sample whose transmissivity is being measured is placed between the second and third collimators.