By William R. Hamilton

Hamilton discovered the system of quaternions on 16th October, 1843. On the following day, he wrote a letter to his friend and fellow-mathematician, John T. Graves, describing the train of thought that led to his discovery. This letter was subsequently published in the London, Edinburgh and Dublin Philosophical Magazine and Journal of Science, vol. xxv (1844), pp 489-95.

This letter is available in the following formats:

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D.R. Wilkins(

School of Mathematics

Trinity College, Dublin