George Robarts (or Roberts) Smalley was educated at the University of Cambridge, where he obtained the degree Bachelor of Arts (BA) with first class honours in mathematics in 1845. In April the next year he was appointed as third assistant at the Royal Observatory, Cape of Good Hope, arriving for duty on 8 September. His post was created to continue observations of terrestrial magnetism that had been carried out since 1841 by a detachment of the Royal Artillery in a properly equipped magnetic observatory on the grounds of the Royal Observatory, Cape of Good Hope. Responsibility for the observations was transferred from the Army to the Admiralty in July 1846 and a reduced observational programme continued under the supervision of H.M. Astronomer at the Cape, Thomas Maclear*. Smalley's duties were confined to the magnetic observatory. Five times per day, six days per week (Sundays excluded) he observed the magnetic declination, magnetic inclination, horizontal and vertical field strengths, and atmospheric conditions.
Smalley left the observatory on 31 October 1851 and was succeeded as third assistant by P. Morton*. Meanwhile, in December 1850, he had been appointed professor of mathematics at the South African College, Cape Town, at that time the only institution in southern Africa providing secondary education. However, his salary of £100 per year plus fees proved inadequate and at the end of November 1851 he gave four months notice of his resignation. Presumably he left South Africa in 1852. Years later he was in Australia, where he published five papers in the fields of astronomy and geophysics in quick succession, all in the Transactions of the Philosophical Society of New South Wales. These dealt with the theory of Encke's comet (1866), possible relations between geological changes and astronomical observations (1866), the present state of astronomical, magnetical and meteorological science (1866), the mutual influence of clock pendulums (1867), and the value of earth temperatures (1868). He also wrote a book, Facts and formulae in pure mathematics and natural philosophy, of which a new edition, revised and enlarged by J. McDowell, was published in Cambridge in 1881.