Searle's pattern. The instrument consisting of two frames connected by a link. The frames are fitted with self centring chucks. An accurately graduated micrometer screw to read to 01 mm is fitted on one frame. One end of a sensitive spirit level is pivoted to one of one of the frame, the other end rests on the points of a micrometer screw fitted in the other frame. The bubble of the level is adjusted to its zero mark and the reading of the micrometer observed. The load is then applied and by turning the micrometer screw the bubble is again adjusted to zero. The reading is observed and the difference between the reading gives the extension of the wire. Complete with chucks, ceiling attachment and tension weight. With case.