FTP, identify this Russian mathematician, best known for his development of a theory of non-Euclidan geometry.
The first English translations of this mathematician's work were done by G.B. Halsted in the early 20th century.  Possibly the greatest student of Johann Bartels, this man preceded Swiss mathematician Carl Graeffe in finding a method for approximating the roots of algebraic equations.  While working at the University of Kazan he did his most important work, similar to that being done by Hungarian Janos Bolyai.  FTP, identify this Russian mathematician, best known for his development of a theory of non-Euclidan geometry.
The first English translations of this mathematician's work were done by G.B. Halsted in the early 20th century.  
Nikolay Lobachevsky