Matrix notation was investigated by the British mathematician Arthur Cayley
around 1858. Caley formalized matrix algebra, along with the American mathematicians
Benjamin and Charles Pierce. Also, by the start of the 19th century
Carl Gauss (1777–1855) had proved that transformations were not commutative,
i.e. T1 × T2 = T2 × T1, and Caley’s matrix notation would clarify such
observations. For example, consider the transformation T1: