Imágenes de páginas

be, either by some moisture the body yieldeth, or else by the moist air thickened against the hard body. But it is plain that it is the latter; for that we see wood painted with oil colour, will sooner gather drops in a moist night, than wood alone; which is caused by the smoothness and closeness; which letteth in no part of the vapour, and so turneth it back, and thickeneth it into dew. We see also, that breathing upon a glass, or smooth body, giveth a dew; and in frosty mornings, such as we call rime frosts, you shall find drops of dew upon the inside of glass windows; and the frost itself upon the ground is but a version or condensation of the moist vapours of the night, into a watery substance : dews likewise, and rain, are but the returns of moist vapours condensed; the dew, by the cold only of the sun's departure, which is the gentler cold; rains, by the cold of that which they call the middle region of the air; which is the more violent cold.

82. It is very probable, as hath been touched, that that which will turn water into ice, will likewise turn air some degree nearer unto water. Therefore try the experiment of the artificial turning water into ice, whereof we shall speak in another place, with air in place of water, and the ice about it. And although it be a greater alteration to turn air into water, than water into ice; yet there is this hope, that by continuing the air longer time, the effect will follow : for that artificial conversion of water into ice, is the work of a few hours; and this of air may be tried by a month's space, or the like. Experiments in consort touching induration of bodies.

INDURATION, or lapidification of substances more soft, is likewise another degree of condensation ; and is a great alteration in nature. The effecting and accelerating thereof is very worthy to be inquired. It is effected by three means. The first is by cold; whose property is to condense and constipate, as hath been said. The second is by heat; which is not proper but by consequence; for the heat doth attenuate; and by attenuation doth send forth the spirit and moister part of a body ; and upon that, the more gross of the tangible parts do contract and serre themselves together; but to avoid vacuum, as they call it, and also to munite themselves against the force of the fire, which they have suffered. And the third is by assimilation; when a hard body assimilateth a soft, being contiguous to it.

The examples of induration, taking them promiscuously, are many: as the generation of stones within the earth, which at the first are but rude earth or clay: and so of minerals, which come, no doubt, at first of juices concrete, which afterwards indurate : and so of porcellane, which is an artificial cement, buried in the earth a long time; and so the making of brick and tile: also the making of glass of a certain sand and brake-roots, and some other matters ; also the exudations of rock-diamonds and crystal, which harden with time; also the induration of beadamber, which at first is a soft substance; as appeareth by the flies and spiders which are found in it; and many more: but we will speak of them distinctly.

83. For indurations by cold, there be few trials of it; for we have no strong or intense cold here on the surface of the earth, so near the beams of the sun, and the heavens. The likeliest trial is by snow and ice; for as snow and ice, especially being holpen and their cold activated by nitre, or salt, will turn water into ice, and that in a few hours; so it may be, it will turn wood or stiff clay into stone, in longer time. Put therefore into a conserving pit of snow and ice, adding some quantity of salt and nitre, a piece of wood, or a piece of tough clay, and let it lie a month

84. ANOTHER trial is by metalline waters, which have virtual cold in them. Put therefore wood of clay into smith's water, or other metalline water, and try whether it will not harden in some reasonable time. But I understand it of metalline waters that come by washing or quenching; and not of strong waters that come by dissolution; for they are too corrosive to consolidate.

or more.

85. It is already found that there are some natural spring waters, that will inlapidate wood; so that you shall see one piece of wood, whereof the part above the water shall continue wood; and the part under water shall be turned into a kind of gravelly stone. It is likely those waters are of some metalline mixture; but there would be more particular inquiry made of them. It is certain, that an egg was found, having lain many years in the bottom of a mote, where the earth had somewhat overgrown it; and this

egg was come to the hardness of a stone, and had the colours of the white and yolk perfect, and the shell shining in small grains like sugar or alabaster. : 86. ANOTHER experience there is of induration by cold, which is already found; which is, that metals themselves are hardened by often heating and quenching in cold water: for cold ever worketh most potently upon heat precedent. 2. 87. For induration by heat, it must be considered, that heat, by the exhaling of the moister parts, doth either harden the body, as in bricks, tiles, etc. or if the heat be more fierce, maketh the grosser part itself run and melt; as in the making of ordinary glass; and in the vitrification of earth, as we see in the inner parts of furnaces, and in the vitrification of brick, and of metals. And in the former of these, which is the hardening by baking without melting, the heat hath these degrees; first, it indurateth, and then maketh fragile; and lastly it doth incinerate and calcinate.

88. But if you desire to make an induration with toughness, and less fragility, a middle way would be taken; which is that which Aristotle hath well noted; but would be thoroughly verified. It is to decoct bodies in water for two or three days; but they must be such bodies into which the water will not enter ; as stone and metal: for if they be bodies into which the water will enter, then long seething with rather soften than indurate them; as hath been tried in eggs, etc. therefore softer bodies must be put into bottles, and the bottles hung into water seething,


with the mouths open above the water, that no water may get in; for by this means the virtual heat of the water will enter; and such a heat, as will not make the body adust or fragile; but the substance of the water will be shut out. This experiment we made; and it sorted thus. It was tried with a piece of freestone, and with pewter, put into the water at large. The free-stone we found received in some water; for it was softer and easier to scrape than a piece of the same stone kept dry. But the pewter into which no water could enter, became more white, and liker to silver, and less flexible by much. There were also put into an earthen bottle, placed as before, a good pellet of clay, a piece of cheese, a piece of chalk, and a piece of free-stone. The clay came forth almost of the hardness of stone; the cheese likewise very hard, and not well to be cut; the chalk and the free-stone much harder than they were. The colour of the clay inclined not a whit to the colour of brick, but rather to white, as in ordinary drying by the sun. Note, that all the former trials were made by a boiling upon a good hot fire renewing the water as it consumed, with other hot water; but the boiling was but for twelve hours only; and it is like that the experiment would have been more effectual, if the boiling had been for two or three days, as we prescribed before.

89. As touching assimilation, for there is a degree of assimilation even in inanimate bodies, we see examples of it in some stones in clay-grounds, lying near to the top of the earth, where pebble is; in which you may manifestly see divers pebbles gathered together, and a crust of cement or stone between them, as hard as the pebbles themselves ; and it were good to make a trial of purpose, by taking clay, and putting in it divers pebble stones, thick set, to see whether in continuance of time, it will not be harder than other clay of the same lump, in which no pebbles are set. We see also in ruins of old walls, especially towards the bottom, the mortar will become as hard as the brick : we see also, that the wood on the sides of vessels of wine, gathereth a crust of tartar, harder than the wood itself; and scales likewise grow to the teeth, harder than the teeth themselves.

90. Most of all, induration by assimilation appeareth in the bodies of trees and living creatures : for no nourishment that the tree receiveth, or that the living creature receiveth, is so hard as wood, bone, or horn, etc, but is indurated after by assimilation. Experiment solitary touching the version of

water into air. 91. The eye of the understanding is like the eye of the sense: for as you may see great objects through small crannies, or levels; so you may see great axioms of nature through small and contemptible instances. The speedy depredation of air upon watry moisture, and version of the same into air, appeareth in nothing more visible, than in the sudden discharge or vanishing of a little cloud of breath or vapour from glass, or the blade of a sword, or any such polished body, such as doth not at all detain or imbibe the moisture; for the mistiness scattereth and breaketh up suddenly. But the like cloud, if it were oily or fatty, will not discharge; not because it sticketh faster; but because air preyeth upon water; and flame and fire upon oil; and therefore to take out a spot of grease they use a coal upon brown paper; because fire worketh upon grease or oil, as air doth upon water. And we see paper oiled, or wood oiled, or the like, last long moist; but wet with water, dry or putrify sooner. The cause is, for that air meddleth little with the moisture of oil.

Experiment solitary touching the force of union.

92. THERE is an admirable demonstration in the same trifling instance of the little cloud upon glass, or gems, or blades of swords, of the force of union, even in the least quantities, and weakest bodies, how much it conduceth to preservation of the present form, and the resisting of a new. For mark well the discharge of that cloud; and you shall see it

« AnteriorContinuar »