Abstract: The coagulometer for measuring the clotting time of liquids such as blood has a turning sample vessel whose axis of turning is at an angle to the vertical. Within the vessel an annular space is formed. The amount of liquid to be tested placed in the annular space is such that no complete ring stretching right the way round the axis of turning is formed when the vessel is not being turned or is being turned before clotting has started. When however clotting takes place sample liquid is transported up the sloping lower face of the annular space, such motion being sensed by a recording system.