Robert Perceval Graves , Dictionary of National Biography… (1890)
“ For many years Graves and Hamilton maintained an active correspondence, in which they vied with each other in endeavours to carry into space a full and coherent interpretation of imaginaries. Graves worked as having for his aim the perfecting of algebraic language; Hamilton had persistently in view the higher object of arriving at the meaning of the science and its operations. These conjoint labours bore their great fruit in 1843, when Hamilton discovered quaternions, and it was to Graves that he made on 17 Oct. ”
