At the Long Island College Hospital (Brooklyn, N. Y.), where a large number of myelographic examinations are performed, it has become apparent to us that a simple means for recording on film the degree of table inclination would be of great value. Accordingly, we have designed a simple indicator which records accurately the degree of table tilt on each spot film. This indicator consists primarily of a mercury droplet enclosed in a hollow glass tube which has been bent to form a semicircle and sealed at both ends. The tube is encased in a block of wood or plastic (Fig. 1) so grooved that it may be affixed to the spot-film device. The system is semiopaque except for the mercury droplet; thus a shadow will be cast on both the fluoroscopic screen and the exposed film. The glass tube will appear as a rectangular column, within which lies the opaque droplet. Since the indicator depends upon gravity for operation, it follows that the mercury droplet will appear in the center of the column when the table is horiz...