Dictionarium Polygraphicum. Blackness.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol I.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
BLACKNESS, is the quality of a Black body or a colour arising from such a texture, and situation of the superficial parts of the body, as does as it were deaden or rather absorb the light, falling on it without reflecting any or very little of it to the eye.

In which sense Blacknes; stands directly oppos'd to whiteness, which consists in such a texture of parts, as indifferently reflects all the rays thrown upon it, of what colour soever they be.

Sir Isaac Newton has shewn in his opticks, that for the production of Black colours, the corpuscles must be less than whose which inhibit any other colours; because where the sizes of the component particles are greater, there is too much light reflected to constitute this colour; but if there be a little less than is requisite to reflect the white, and the very faint blue of the first order, they will reflect so little light, as to appear intensely Black; and yet may, perhaps, reflect it variously to and fro within them so long, till it happen to be stifled and lost; by which means they will appear Black, in all positions of the eye, without any transparency.

And from hence it appears why fire, and putrefaction by dividing the particles of substances, turn them Black; why small quantities of Black substances impart their colour very freely, and intensely to other substances to which they are apply'd; the minute particles of these by reason of their very great number easily over-spreading the gross particles of others; hence also appears why glass ground very elaborately with sand on a copper plate till it be well polish'd makes the sand, together with what by rubbing is worn off from the glass and copper, become very Black; and why Black substances do soonest of all others become hot in the light of the sun, and burn (which effect may proceed partly from the multitude of refractions in a little room, and partly from the easy commotion of so very small particles;) and also why Blacks are usually a little inclin'd towards a bluish colour; for that they are so, may be seen by illuminating white paper by light reflecting from Black substances, where the paper will usually appear of a bluish white; and the reason is, that Black borders on the obscure blue of the first order of colours, and therefore reflects more rays of that colour than of any other.

It is necessary also to the production of Blacknes; in any bodies, that the rays be stopp'd, retain’d and lost in them; and these conceive heat (by means of a burning glass, &c.) more easily than other bodies; because the light that falls upon them is not reflected outwards, but enters the bodies, and is often reflected and refracted in them, till it be stifled and lost. See LIGHT and COLOUR.

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