, in Arithmetic, is when the proportion of any terms, or quantities, is in the natural or direct order in which they stand; being the opposite to inverse, which considers the proportion in the inverted order of the terms. So, 3 : 4 :: 6 : 8 directly; or 3 : 4 :: 8 : 6 inversely.

Rule of Three Direct, is when both pairs of terms are in direct proportion.


, in Astronomy. A planet is said to be di- | rect, or its motion direct, when it goes forward by its proper motion in the zodiac, according to the succession or order of the signs; or when it appears so to do, to an observer standing upon the earth. Whereas it is said to be, or to move retrograde, when it appears to go the contrary way, or backward; and to be stationary, when it seems not to move either way.

Direct Dials. See Dial and Dialling.


, in Optics. Direct vision is that performed by direct rays; in contradistinction to vision by refracted, or reflected rays. Direct vision is the subject of Optics, which prescribes the laws and rules of it.

Direct Rays, are those which pass on in right lines from the object to the eye, without being turned out of their rectilinear direction by any intervening body, either opaque or pellucid; or without being either reflected or refracted.

Direct Sphere. See Right Sphere.

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

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