May I begin by expressing my gratitude to the Master of Trinity and his Council for their trust in assigning to me the privilege of giving the Centenary Lectures in memory of one of the most distinguished members of the College and of the University. I knew Eddington as a member of the Fellowship of Trinity during the early and the middle thirties when, besides Eddington, it included J. J. Thomson, Ernest Rutherford, George Trevelyan, Douglas Adrian, Donald Robertson, G. H. Hardy, J. E. Littlewood, and a host of others. It is hardly necessary for me to say how much it means to me to have been a member of that society during those years and to be asked now, almost fifty years later, to give these lectures in honour of one whose personal friendship I was fortunate to enjoy.

When Eddington died in November 1944 at the age of sixtytwo, Henry Norris Russell, his great contemporary across the Atlantic, wrote: ‘The death of Sir Arthur Eddington deprives astrophysics of its most distinguished representative.’ I have taken my cue from Russell for the substance of this, the first of my two lectures.

Before I turn to an assessment of Eddington's contributions to astronomy and to astrophysics, I should like to start with a few biographical notes which may give some impression of the manner of man he was.