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some covert. titious moisture of living creatures, which maketh as well the feathers in birds, as the hair in beasts, passeth in birds through a finer and more delicate strainer. than it doth in beasts: for feathers pass through quills; and hair through skin.

The true cause is, that the excrement

6. THE clarifying of liquors by adhesion, is an inward percolation; and is effected, when some cleaving body is mixed and agitated with the liquors; whereby the grosser part of the liquor sticks to that cleaving body; and so the finer parts are freed from the grosser. So the apothecaries clarify their syrups by whites of eggs, beaten with the juices which they would clarify; which whites of eggs gather all the dregs and grosser parts of the juice to them; and after the syrup being set on the fire, the whites of eggs themselves harden, and are taken forth. So hippocras is clarified by mixing with milk, and stirring it about, and then passing it through a woollen bag, which they call Hippocrates's Sleeve, and the cleaving nature of the milk draweth the powder of the spices, and grosser parts of the liquor to it; and in the passage they stick upon the woollen bag.

7. THE clarifying of water is an experiment tending to health; besides the pleasure of the eye, when water is crystalline. It is effected by casting in and placing pebbles at the head of a current, that the water may strain through them.

8. It may be, percolation doth not only cause clearness and splendour, but sweetness of savour; for that also followeth as well as clearness, when the finer parts are severed from the grosser. So it is found, that the sweats of men, that have much heat, and exercise much, and have clean bodies, and fine skins, do smell sweet; as was said of Alexander; and we see commonly that gums have sweet odours.

Experiments in consort, touching motion of bodies upon their pressure.

9. TAKE a glass, and put water into it, and wet your finger, and draw it round about the lip of the

glass, pressing it somewhat hard; and after you have drawn it some few times about, it will make the water frisk and sprinkle up in a fine dew. This instance doth excellently demonstrate the force of compression in a solid body: for whensoever a solid body, as wood, stone, metal, etc. is pressed, there is an inward tumult in the parts thereof seeking to deliver themselves from the compression: and this is the cause of all violent motion. Wherein it is strange in the highest degree, that this motion hath never been observed, nor inquired; it being of all motions the most common, and the chief root of all mechanical opérations. This motion worketh in round at first, by way of proof and search which way to deliver itself: and then worketh in progress, where it findeth the deliverance easiest. In liquors this mo tion is visible; for all liquors strucken make 'round circles, and withal dash; but in solids, which break not, it is so subtile, as it is invisible; but nevertheless bewrayeth itself by many effects; as in this instance whereof we speak. For the pressure of the finger, furthered by the wetting, because it sticketh so much the better unto the lip of the glass, after some continuance, putteth all the small parts of the glass into work; that they strike the water sharply; from which percussion that sprinkling cometh.

10. IF you strike or pierce a solid body that is brittle, as glass, or sugar, it breaketh not only where the immediate force is; but breaketh all about into shivers and fitters; the motion, upon the pressure, searching all ways, and breaking where it findeth the body weakest.

11. THE powder in shot, being dilated into such a flame as endureth not compression, moveth likewise in round, the flame being in the nature of a liquid body, sometimes recoiling, sometimes breaking the piece, but generally discharging the bullet, because there it findeth easiest deliverance.

12. THIS motion upon pressure, and the reciprocal thereof, which is motion upon tensure, we use to call, by one conimon name, motion of liberty; which is,

when any body, being forced to a preternatural extent or dimension, delivereth and restoreth itself to the natural: as when a blown bladder, pressed, riseth again; or when leather or cloth tentured, spring back. These two motions, of which there be infinite instances, we shall handle in due place.

13. THIS motion upon pressure is excellently also demonstrated in sounds; as when one chimeth upon a bell, it soundeth; but as soon as he layeth his hand upon it, the sound ceaseth: and so the sound of a virginal string, as soon as the quill of the jack falleth from it, stoppeth. For these sounds are produced by the subtile percussion of the minute parts of the bell, or string, upon the air; all one, as the water is caused to leap by the subtile percussion of the minute parts of the glass, upon the water, whereof we spake a little before in the ninth experiment. For you must not take it to be the local shaking of the bell, or string, that doth it: as we shall fully declare, when we come hereafter to handle sounds.

Experiments in consort, touching separations of bodies by weight.

14. TAKE a glass with a belly and a long neb; fill the belly, in part, with water: take also another glass, whereinto put claret wine and water mingled; reverse the first glass, with the belly upwards, stopping the neb with your finger; then dip the mouth of it within the second glass, and remove your finger: continue it in that posture for a time; and it will unmingle the wine from the water: the wine ascending and settling in the top of the upper glass; and the water descending and settling in the bottom of the lower glass. The passage is apparent to the eye; for you shall see the wine, as it were, in a small vein, rising through the water. For handsomeness sake, because the working requireth some small time, it were good you hang the upper glass upon a nail. But as soon as there is gathered so much pure and unmixed water in the bottom of the lower glass, as that the mouth of the upper glass dippeth into it, the motion ceaseth.

15. LET the upper glass be wine, and the lower water; there followeth no motion at all. Let the upper glass be water pure, the lower water coloured, or contrariwise, there followeth no motion at all. But it hath been tried, that though the mixture of wine and water, in the lower glass, be three parts water and but one wine, yet it doth not dead the motion, This separation of water and wine appeareth to be made by weight; for it must be of bodies of unequal weight, or else it worketh not; and the heavier body must ever be in the upper glass. But then note withal, that the water being made pensile, and there being a great weight of water in the belly of the glass, sustained by a small pillar of water in the neck of the glass, it is that which setteth the motion on work: for water and wine in one glass, with long standing, will hardly sever.

16. THIS experiment would be extended from mixtures of several liquors, to simple bodies which consist of several similar parts: try it therefore with brine or salt-water, and fresh-water; placing the salt-water, which is the heavier, in the upper-glass; and see whether the fresh will come above. Try it also with water thick sugared, and pure water; and see whether the water, which cometh above, will lose its sweetness: for which purpose it were good there were a little cock made in the belly of the upper glass.

Experiments in consort, touching judicious and accurate infusions, both in liquors and air.

17. IN bodies containing fine spirits, which do easily dissipate, when you make infusions, the rule is; a short stay of the body in the liquor, receiveth the spirit; and a longer stay confoundeth it; because it draweth forth the earthy part withal, which embaseth the finer. And therefore it is an error in physicians, to rest simply upon the length of stay for increasing the virtue. But if you will have the infusion strong, in those kinds of bodies which have fine spirits, your way is not to give longer time, but to repeat the

infusion of the body oftener. Take violets, and infuse a good pugil of them in a quart of vinegar; let them stay three quarters of an hour, and take them forth, and refresh the infusion with like quantity of new violets, seven times; and it will make a vinegar so fresh of the flower, as if, a twelvemonth after, it be brought you in a saucer, you shall smell it before it come at you. Note, that it smelleth more perfectly of the flower a good while after than at first.

18. THIS rule, which we have given, is of singular use for the preparations of medicines, and other infusions. As for example: the leaf of burrage hath an excellent spirit to repress the fuliginous vapour of dusky melancholy, and so to cure madness: but nevertheless, if the leaf be infused long it yieldeth forth but a raw substance, of no virtue: therefore I suppose, that if in the must of wine, or wort of beer, while it worketh, before it be tunned, the burrage stay a small time, and be often changed with fresh; it will make a sovereign drink for melancholy passions. And the like I conceive of orange flowers.

19. RHUBARB hath manifestly in it parts of contrary operations: parts that purge; and parts that bind the body: and the first lie looser, and the latter lie deeper: so that if you infuse rhubarb for an hour, and crush it well, it will purge better, and bind the body less after the purging than if it had stood twenty-four hours; this is tried: but I conceive like wise, that by repeating the infusion of rhubarb, several times, as was said of violets, letting each stay in but a small time; you may make it as strong a purging medicine as scammony. And it is not a small thing won in physic, if you can make rhubarb, and other medicines that are benedict, as strong purgers as those that are not without some malignity.

20. PURGING medicines, for the most part, have their purgative virtue in a fine spirit; as appeareth by that they endure not boiling without much loss of virtue. And therefore it is of good use in physic, if you can retain the purging virtue, and take away the unpleasant taste of the purger which it is like

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