Plate, figure 4 showing cotidal rings surrounding an island by William Whewell Figure 4 showing a diagram of cotidal rings surrounding an island. A later version of this diagram is found at PT/34/1/5. Subject: Hydrography Published in Philosophical Transactions as 'The Bakerian Lecture.—Researches on the tides. Thirteenth series. On the tides of the Pacific, and on the diurnal inequality'. Written by Whewell in Trinity Lodge, Cambridge. Received by the Royal Society on 11 November 1847. Read 16 December 1847. 8 November 1847