An electronic data set of tidal measurements at St. Helena in 1761 by Nevil Maskelyne is described. These data were first analysed by Cartwright in papers on changing tides, but his data files were never archived. The now newly digitised Maskelyne data have been reanalysed in order to obtain an updated impression of whether the tide has changed at that location in over two and a half centuries. Our main conclusion is that the major tidal constituent (M2) has changed little.

Observations of sea level, taken manually by reading a tide pole, were carefully taken at a number of locations around Ireland in 1842 as part of the first land survey of Ireland. Our study investigates how useful this type of sea level observation is for understanding mean sea level and tidal change. We find that when carefully adjusted for seasonal, meteorological, and astronomical factors, these data can provide important insights into changing sea levels.

This special issue marks the 100th anniversary of the founding of the Liverpool Tidal Institute (LTI). The preface gives a history of the LTI founding and of its first two directors. It also gives an overview of LTI research on tides. Summaries are given of the 26 papers in the special issue. Their topics could be thought of as providing a continuation of the research first undertaken at the LTI. They provide an interesting snapshot of work on tides now being made by groups around the world.

The Liverpool Tidal Institute's (LTI) 100th anniversary was in 2019, and it acquired a reputation using tide prediction machines (TPMs). We describe the principles of a TPM, how many were made and Doodson's method to determine harmonic constants from tidal data to predict the tides. Although only three TPMs were used at the LTI, Doodson oversaw the design and manufacture of several others. We show how the UK, and Doodson particularly, played a central role in this area of science.

From the early work of Prince Albert I of Monaco, the first president of the International Association for the Physical Sciences of the Oceans, to today, the Association has promoted and supported international research and cross-cutting activities in ocean sciences, building on the work of the many far-sighted scientists who, over the last century, have addressed seemingly intractable problems. This paper describes key events in IAPSO's history and the roles played by the scientists involved.