paraboloidal

The central rays of light are blocked out by means of an opaque stop while the peripheral rays are reflected from the paraboloidal sides of the condenser and refracted by the object viewed.

The Elements of Bacteriological Technique A Laboratory Guide for Medical, Dental, and Technical Students. Second Edition Rewritten and Enlarged.

Its upper surface is paraboloidal in shape, as a spherical surface will not unite in a sharp focus the rays coming from a distant object.

The New Heavens George Ellery Hale 1903

When first seen, it wore the aspect of a nebula; later it put on the distinctive garb of a comet; it next appeared as a star; finally, it dilated, first in a spherical, then in a paraboloidal form, until May 5,

A Popular History of Astronomy During the Nineteenth Century Fourth Edition 1874

The paraboloidal shape of the bright envelope separated by a dark interval from the head of the great comet of 1811, and constituting, as it were, the _root_ of its tail, seemed to the astronomer of Bremen to reveal the presence of a double repulsion; the expelled vapours accumulating where the two forces, solar and cometary, balanced each other, and being then swept backwards in a huge train.

A Popular History of Astronomy During the Nineteenth Century Fourth Edition 1874

Similiar paraboloidal forms had, nevertheless, occasionally been seen to make an integral part of earlier coronas; and it remains extremely doubtful whether Schaeberle's "eclipse-comet" was justly entitled to the character claimed for it.

A Popular History of Astronomy During the Nineteenth Century Fourth Edition 1874