Abstract: The tracking apparatus (2) comprises a frame (4) mounted on a rigid stand that is orientated such that the longitudinal axis (6) of the frame is at an angle above horizontal. The frame (4) comprises opposite frame members (8 and 10) between which is mounted reservoirs in the form of hollow side tanks (12 and 14). Each of the tanks is partially filled with a liquid refrigerant. The interior of the tank (12) is connected to flexible bellows (16) through the passageway of a conduit (18). The interior of the tank (14) is connected to flexible bellows (20) through the passageway of a further conduit (22). An actuating mechanism (24) is secured to frame member (10) of the frame. The actuating mechanism comprises a further frame (26) to which the outer ends of bellows (16 and 20) are fastened. The inner ends of the bellows are connected by a rigid shaft (28) which is driven back and forth by the bellows (16 and 20) to effect rotation of drive wheel (30) of the actuating mechanism.