Sophia Elizabeth De Morgan (née Frend; 10 November 1809–5 January 1892) was an English spiritualist writer and activist.
[9] Around 1832, Sophia expressed scepticism about a phrenological reading of Ada's head, by James De Ville, that had been arranged by her mother.
[10] In June 1833 Ada visited Charles Babbage and saw his difference engine, and Sophia reported that she had understood the principle of the machine.
[18] Her views on spiritualism adapted the philosophy of Emanuel Swedenborg, and influenced in particular Evelyn Pickering, who married her son William.
[25] Sophia married Augustus De Morgan on 3 August 1837, unconventionally for the period at the registry office in St Pancras.