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Published online by Cambridge University Press: 14 August 2015
Twenty years of time and latitude observations made with the Herstmonceux Photographic Zenith Tube have been analysed to determine the phase and amplitude of deflexions of the local vertical at the frequency of the semi-diurnal M2 tide. The results have been compared with predictions incorporating new calculations of the gravitational attraction due to the M2 tides in the surrounding seas. The effects of the zonal Mm and Mf tides on the time observations have also been determined and compared with existing theory. In both cases the agreement is reasonably good.