A versatile tide machine and associated activity recorder

The paper describes the design and use of a tide machine capable of producing near-sinusoidal hydrostatic pressure cycles varying in period from 12 to 999 min and in amplitude from 0·4 to 3·2 m. In conjunction with infra-red detection units and a microprocessor logging system the apparatus can be used to detect and record the response of a variety of organisms to cyclic pressure changes.