, in Algebra, are the letters, symbols, marks, or characters, which represent the quantities in any operation or equation.

This short and advantageous way of notation was chiefly introduced by Vieta, about the year 1590; and by means of which he made many discoveries in algebra, not before taken notice of.

The reason why Vieta gave this name of Species to the letters of the alphabet used in algebra, and hence called Arithmetica Speciosa, seems to have been in imitation of the Civilians, who call cases in law that are put abstractedly, between John a Nokes and Tom a Stiles, between A and B; supposing those letters to stand for any persons indefinitely. Such cases they call Species: whence, as the letters of the alphabet will also as well represent quantities, as persons, and that also indefinitely, one quantity as well as another, they are properly enough called Species; that is general symbols, marks, or characters. From whence the literal algebra hath since been often called Specious Arithmetic, or Algebra in Species.


, in Optics, the image painted on the retina by the rays of light reflected from the several points of the surface of an object, received in by the pupil, and collected in their passage through the crystalline, &c.

Philosophers have been in great doubt, whether the Species of objects, which give the soul an occasion of seeing, are an effusion of the substance of the body; or a mere impression which they make on all ambient bodies, and which these all reflect, when in a proper disposition and distance; or lastly, whether they are not some other more subtile body, as light, which receives all these impressions from bodies, and is continually sent and returning from one to another, with the different impressions and figures it has taken. But the moderns have decided this point by their invention of | artificial eyes, inwhich the Species of objects are received on a paper, in the same manner as they are received in the natural eye.

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Entry taken from A Mathematical and Philosophical Dictionary, by Charles Hutton, 1796.

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