He regarded as his greatest achievement his finding of the surface area and volume of a

*sphere*, which he obtained by proving these are 2/3 the surface area and volume of a cylinder circumscribing the*sphere*. Apollonius of Perga (c. 262–190 BC) made significant advances to the study of*conic**sections*, showing that one can obtain all three varieties of*conic**section*by varying the angle of the plane that cuts a double-napped cone. He also coined the terminology in use today for*conic**sections*, namely parabola ("place beside" or "comparison"), "ellipse" ("deficiency"), and "hyperbola" ("a throw beyond").