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Webster 1913 Edition
Porism
Po′rism
,Noun.
[Gr. [GREEK] a thing procured, a deduction from a demonstration, fr. [GREEK] to bring, provide: cf. F.
porisme
.] 1.
(Geom.)
A proposition affirming the possibility of finding such conditions as will render a certain determinate problem indeterminate or capable of innumerable solutions.
Playfair.
2.
(Gr. Geom.)
A corollary.
Brande & C.
☞ Three books of porisms of Euclid have been lost, but several attempts to determine the nature of these propositions and to restore them have been made by modern geometers.
Webster 1828 Edition
Porism
PO'RISM
,Noun.
In geometry, a name given by ancient geometers to two classes of propositions. Euclid gave this name to propositions involved in others which he was investigating, and obtained without a direct view to their discovery. These he called acquisitions, but such propositions are now called corollaries. A porism is defined, 'a proposition affirming the possibility of finding such conditions as will render a certain problem indeterminate or capable of innumerable solutions.' It is not a theorem, nor a problem, or rather it includes both. It asserts that a certain problem may become indeterminate, and so far it partakes of the nature of a theorem, and in seeking to discover the conditions by which this may be effected, it partakes of the nature of a problem.