An ellipse is a circle bent a little, and the ellipse in which the earth actually moves comes from varying attraction and repulsion.

It is an ellipse of which the transverse axis is 580 feet in length and its conjugate diameter 480; but it is not so much the length and breadth as the solidity of this building that strikes the traveller with astonishment.

"Among mathematical investigations I find: Theory of the Moon's brightness, Motion of a body in an ellipse round two centres of force, Various differential equations, Numerical computation of sin pi from series, Numerical computation of sines of various arcs to 18 decimals, Curvature of surfaces in various directions, Generating functions, Problem of sound.

From the first law of Kepler, that every planet moves in an ellipse with the sun in one of its foci, he drew the still more general inference that the force by which the planet moves round that focus varies inversely as the square of its distance from the focus.

The form of the dome has one inconvenience, viz., the embrasure in it is necessarily very oblique, and offers quite an elongated ellipse to blows, and the edges of the bevel upon a portion of the circumference are not strong enough.