315,165. May, J. Oct. 26, 1928. Optical instruments; anthropometrical appliances.-In apparatus for observing changes in the surface of the sole of a foot when resting on a plate b and subjected to a load and unloaded, a casing a below the plate accommodates a mirror c which is adapted to be withdrawn partly from the casing through an open end thereof, and it is then at such an angle to the plate that the desired observation can be made by looking into the projecting portion of the mirror. As shown, the open end of the casing is fitted with a hinged door to which the outer end of the mirror is pivoted, and in this way when the door is opened the mirror is brought out and brought to the correct angular position for the observation to be made. A projection n screens the mirror from light from the lamp c which is arranged in front of a platform g and covered by a frosted glass plate l. By the provision of an abutment o on the mirror and a spring contact-carrying arm k projecting up through a slot in the platform, the lamp circuit is automatically made and broken as the mirror is withdrawn from, and retired into, the casing. The sides of the mirror may be provided with hooks which, by engagement with guide-bars m, limit the forward movement of the mirror.