Imágenes de páginas

these kinds of efficients that air is always hecessary to the form of whiteness, or that white ness is generated only by, transparent bodieši which two positions are absolutely false, and rejected by numerous exclusions t. It will rather appear, without the interposition of the air, &c. that the bodies perfectly uniform, or similar, in their optical parts, prove transparent : that those which have the simple texture, or arrangement of their parts disturbed, are white; that a dissimilarity in the regular texture of bodies, af* fords all colours, except black; and that a dissimilarity in a compound, absolutely irregular, and confused texture, constitutes - blackness 1: And, for an instance advancing to destruction in the same nature of whiteness, we have it in froth subsided, or snow dissolved; for water deposites its whiteness, and puts on transparency, upon becoming entire, without any intermixture of

Such as the pounding of glass, the agitating of water, &c. upon which the transparency ensues.

† According to the procedure of Tuble IV. Aph. 18. thus ceruse is made of lead, an opake pulpy mass makes white paper, &c. white minerals are found in the earth, white enas mels are made in the fire, &c..

tsPerhaps these intimations 'carry the enquiry into the causes of colours, on the side of the coloured body, farther than has been generally followed. See Mr. Boyle of Cool lours, and Sir Isaac Newten's Optics. 9.14 Hvoda 992

<3 We must by no meanis omit, that under travels ling instances should be comprehended, not only those which travel to absolute generation and privation, but such likewise as travel to a greater or less degree of the nature sought, since these also tend to the discovery of the form, as plainly appears both from the definition of a form, above laid down, and the table of comparison . And therefore the instance of paper, which is white when dry, but proves less white when wet, and comes nearer to the state of transparency, upon the exclusion of the air, and the reception of the water, is of the same use as the instances above-mentioned i.

24. (11.) Among the prerogative instances come in the third place the glaring kind, mentioned in our first dawn of doctrine from the form of heat g; which we also call by the name of shining, released, or predominating instances. And these are such as shew the nature searched after naked and standing alone, and this in an eminent manner, or in the highest degree of its power, as being disenthralled and freed from all impediments, or at least by the strength of its

* See above, Aph. 4. * See above, Aph. 13. cite!

Viz. The whiteness and transparency of glass, water, &c; this latter being a kind of intermediate instance; bes twixt the former. fawat y 19999*390 5ks

See above, Aph. 20.00. Jesu 31 Ornal xic bas nepal

own virtue over-ruling, conquering, and subduing them. For as every body may receive many united and concrete forms of natures, it happens that one may repell, depress, break and bind down another, whence all particular forms are obscured. But there are certain subjects, wherein the nature sought after, appears more in its vigour than in others; either through the absence of impediments, or the predominancy of its own virtue. And instances of this kind are what principally shew the form. But in these also caution must be used, and the alertness of the understanding be repressed, for whatever boasts the form, and obtrudes it, so as that it seems to meet the understanding, should be held suspect *; and recourse be had to a careful and severe exclusion t.

For example, if the nature enquired after be heat; then the weather-glass is a glaring instance of the expansive motion, which is, as we said above, a principal part of the form of heats. For flame, though it manifestly shews

niany cer

* As being very apt to deceive; for men have reason be assured,' that the forms of things are not easy to find. And let it be duly weighed and considered,

how tain instances there are of a true and perfect discovery of forms.

+ See above, Tab. IV. Aph. 98.

# See Aph. 12. (37.) 20. ad finem. See Tab. I. II. III. IV. and V.

an expansion, yet by reason of its momentary extinction, it does not exhibít the progress thereof. Again, boiling water, because of the easy transition of the water into vapour and air, does not so well shew the expansion of the water in its own body. Again, ignited iron, and the like bodies, are so far from shewing the progress, that, on the contrary, the expansion itself is not visible to the sense, by reason of the re-action and breaking of the spirit in the compact and gross part* ; but the weather-glass clearly and evidently shews a true progressive, and durable expansion of the air by heat f.

For a second example; let. the nature enquired after be gravity, and then quicksilver will prove a glaring instance, as having a far greater specific gravity than any thing else, except gold, which, however, is not much heavier ; but quicksilver is a better instance for disclosing the form of gravity than gold, because gold being a solid and consistent body, its súperior gravity may seem owing to its solidity; whereas quicksilver is fluid, and full of spirit, and yet proves much heavier than diamond, or any other of those bodies that are esteemed the most solid. Whence it appears that the form of gra

All the five preceding tables are to be consulted on this occasion.,

† See above, Tab. II. III. (37.)

vity or weight resides simply in the quantity of matter and not in solidity, firmness or hardness of texture.

25. In the fourth place come those we call clandestine instances, or instances of twilight, which are in a manner opposite to glaring instances, as shewing the nature enquired after in its weakest virtue and imperfect state, or rudiments, striving or, as its were, first attempting to manifest itself, whilst it remains covered and subdued, or kept under by a contrary nature, And there instances are of extraordinary service in the discovery of forms; because, as the glaring, instances easily lead to differences, so the clandestine instances easily lead to kinds, that is, to those common natures of which the natures éno quired into are no other than limitations*.

For example; let the nature enquired into be consistence or solidity, the contrary of which is liquidity or fluidity, then clandestine instances are such as exhibit some faint and low degree of consistency in a fluid ; suppose a bubble of water which is a kind of consistent and determinate pellicule, 'made of the body of the water. In like manner icicles, if there be water to follow them, lengthen themselves out in a very slender thread, to prevent a discontinuity of the water;

See above, Part It: Aph. 4: Whence it is!

will evidently appear of what great use these instances are.

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