Approximately 275mm length with cast metal bridge mounted on tripod stand adjustable for height & having a levelling knurled head screw fitted on one foot. The bridge has raised end pieces to which are screwed small metal blocks securing either end of a plated steel torsion wire. One block disc slotted to facilitate adjustment for torsion of the wire by means of screw passing through the end piece. At the centre of the wire, a small clamp is fitted carrying a light weight metal pointer with an adjustable counterpoise. From a notch near the tip of the pointer is suspended a small weight pan with a hook fitted to its underside, to hold either wire frame 80x25mm or a metal clip carrying a glass microscope slide 75x25x1.5mm. The tip of the pointer moves over a graduated vertical scale complete with set of weights 1mgm to 1gm