Another collection of philosophical conferences of the French virtuosi upon questions of all sorts for the improving of natural knowledg made in the assembly of the Beaux Esprits at Paris by the most ingenious persons of that nation / render'd into English by G. Havers, Gent. & J. Davies ..., Gent.

CONFERENCE CXXV. Of the Causes of Freezing and Thawing. (Book 125)

AS Heat and Cold are the Efficient Causes of all Meteors, so Driness and Moisture supply Matter for them, sublim'd and made volatil by extraneous Heat. Vapours which make Aqueous Meteors, are of two sorts; some ascend to the Middle Region of the Air, whose coldness condenses them into a Cloud,

which afterwards turnes into Rain, Snow, or Hail: Others, through the weakness of Heat, or tenuity of their Matter unable to ascend, turn into Mists and Dew, and the Serene which pre∣ceedes it, and Frost. For the Matter both of Frost and Dew, is a subtil thin Vapour, which when spread equally and uniform∣ly about the Earth, hinders not the Air's transparency, which therefore in time of Frost is alwayes clear and serene. But their Efficient is distinct; that of Dew is the moderate Coldness of the Night, whence 'tis most frequent in temperate Seasons; that of a Frost is Vehement Cold, whereby being first condens'd, it falls down in form of Crystal: Yet Cold alone suffices not to produce Frost; for then Water, which is cold in an eminent degree, should be alwayes frozen. But some terrene and gross parts must serve for an uniting medium to compact the moist parts of the Water or Vapour, which being naturally fluid, cannot be link'd together but by means of some dry parts fixing and re∣straining their fluidity. Hence the impurest and most com∣pounded Liquors are soonest frozen; distill'd Waters, difficultly, by reason of their simplicity; Vinegar (though cold) never, by reason of the tenuity of its parts. But the surface of waters being full of earthy and gross parts, which could not accompa∣ny the Vapours or Exhalations, drawn up by the Sun's heat, is therefore first frozen; even that of running waters, though not so easily, by reason of their motion makes a divulsion of their parts; as neither Oyle very easily, (by reason of its aërious and unctuous humidity) the Sea, and Hot Spirits; which yet Experience shews are sometimes frozen by Vehement Cold; the Poet in his description of the sharpness of Winter, in his Geor∣gicks, saying, that they cleav'd Wine with hatchets; and the Northern Navigations of the Hollanders, relating that they were detain'd three moneths under the seventy fourth Degree, where their Ships were frozen in the main sea.

The Second said, That Heat and Cold are the immediate Causes of Freezing and Thawing, but 'tis hard to know, Whence that Heat and Cold comes? Now because Cold is onely the Privati∣on of Heat, as Darkness is of Light; we shall sufficiently under∣stand the Causes of Cold and of Freezing, if we know those of Heat which causes Thawing. The truth is, the Sun, whose ap∣proach and remoteness makes the diversities of Seasons accord∣ing to the different mutations which he causes in the qualities of the Air, contribute thereunto, but the Earth helps too; he can∣not do it alone; for we see that the Snow on the Mountains which approach nearest Heaven, is last melted. But the Sun's Rays piercing into the bosome of the Earth, draw out that Fire which is inclos'd in its entralls; and because the Sun re∣moves but a very little from the Aequinoctial Line, therefore that part of the Earth which answers to that of Heaven where the Sun continually resides, is alwayes Hot; and by a contrary Reason, that under the Poles is alwayes extreamly cold: And

even Country-people observe winds to be the Cause of these Effects; for those that blow from the North quarter, bring with them an extream cold Air, which is the cause of Freezing; and those from the South bring on us an Air extreamly heated by the continuall action of the Sun, and so are the cause of Thawing.

The Third said, That Winds being continual, because their matter never fails, it happens that the strongest gets the better of the weakest, and they chase one another; whence Virgil calls them Wrestlers. When the South Winds blow, (which are more frequent, and more gross then the Northern or Eastern, by reason of the Sun's strength in the South, which opens the Pores of the Earth more:) the copious Exhalations which issue out of it, are hotter than those which come out of the Pores of the Northern Earth, which are closed up by Cold, whence the Winds blowing from thence are colder and thinner; just as our breath is cold when we contract our Mouthes, and hot when we dilate them. In like manner, the Exhalations issuing out of the Earth's Pores, are hotter or colder, according as the passages out of which they proceed are more or less dilated, and conse∣quently, cause Freezing or Thawing.

The Fourth said, That the Sun or other Stars are onely re∣mote Causes of Freezing and Thawing; namely, by their Heat which serves to raise the Vapors, which are the next causes there∣of, according as they partake more or less of that external Heat; or, (as the Chymists say) as they are full either of certain nitrous and dissolving Spirits which cause Thawing, or of coagu∣lating ones which cause Freezing; such as those are, harden Plants into Stones, which so presently congeal drops of water in Caves and Water-droppings, and form the Crystals of the Rock. Moreover, just before it freezes, Sinks, and other stinking places smell more strong, by reason that the Spirits and Vapors of the Earth are complicated with those stinks as they issue forth.

The Fifth said, That the Cause of Thawing is to be attribu∣ted to the Heat of the Earth, which exhaling warm Vapors, fi••st heats the bottome of the Water, (for which reason Fish retire thither) then they mollifie and moisten the surface of the Wa∣ter, or the Earth hardned by Cold. Moreover, that Heat which is found in the deepest Mines where the Labourers work naked, and most ordinarily in the Water without enduring any Cold; the veins of Sulphur, Bitumen, Vitriol, and Arsenick, which are found in the entralls of the Earth; the Hot Springs, and the Volcanoes in its surface, sufficiently argue, That if there be not a Central Fire, (as the Pythagoreans held) yet there is a great Heat there, like that of Living Bodies, which concocts Metals, and makes Plants grow. Hence the changes of Air are first dis∣cover'd in Mines by the Vapors arising from beneath, which hinder Respiration, and make the Lamps burn dim, or go quite out. Whereby 'tis evident that they are exhaled by the Heat

of the earth, and not attracted by that of the Sun and Stars, which penetrate but a very little way into the earth. Now as our bodies are inwardly hotter in Winter; so this heat of the earth being concentred in it self, (as appears by Springs which smoke in that season, and by the heat of subterraneous places) raises greater plenty of warm Vapors, which in Winte render the Weather moist and rainy: but when rain or the coldness of the air stops those pores, then those Exhalations being shut up, the Air remains cold, and it freezes; which frost is again dissolv'd by their eruption. For the natural heat of the Earth, being constring'd and render'd stronger by the ambient Cold, drives out hotter and more copious exhalations, which consist either of the rain-water wherewith it is moistned, or of other humi∣dities; and which arriving at the surface of the Earth which is frozen, soften it and fill the air with clouds, which always ac∣company a Thaw, as Serenity do's a Frost.

The Sixth said, That as Hail is nothing but Rain congeal'd, so Frost is nothing but Dew condens'd by the vehemence of Cold, and in the Water 'tis call'd Ice: which coldness conden∣sing the Water, (which is a diaphanous body, and consequent∣ly hath an internal and radical light) is the cause of its white∣ness, which is the beginning of light, as the Stars are the con∣dens'd parts of their Orbs. Unless you had rather ascribe that whiteness to the Air included in the Ice, which also makes the same swim upon the water. An Evidence that Cold alone is not the cause of Freezing; (for Cold alone render bodies more ponderous by condensing their parts, whence Ice should be hea∣vier then Water) but there is requir'd, besides, some hot and dry exhalation, which insinuating into the Water, gives it levity.

The Seventh said, That such bodies as are frozen, are so far from receiving augmentation of parts, that they lose the thinnest of their own; hence a bottle so close stopped that the air can∣not get in to supply the place of the thinner parts which trans∣spire and perish upon freezing, breaks in pieces for avoiding of vacuity. And Wine and Fruits lose their tast upon the loss of their spirits, when they are frozen: which spirits not being able to transpire in Cabbages and other Viscous Plants digest their crudities, and by that means render the same Plants more tender.