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astronomers to a lengthening of the day by
                                         tidal friction.)
                                            Another contribution by Halley to the
                                         verification of Newton’s law was made when
                                         he went to St.  Helena to catalogue the
                                         southern stars. He measured the change in
                                         length of the second’s pendulum in differ-
                                         ent latitudes due to the changes in gravity
                                         foretold by Newton.
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