One brass plate and one iron plate, spot welded together, When heated or cooled, the pointer moves sensitively, which may form at most an angle of 40 from ambient temperatuir to high temperature.

• 由铁和黄铜薄板经点焊而成。配以酒精或煤气灯加热，可作热膨胀实验。指针受热或冷却后转动灵活，最大张角可达40度。