Dolphins playing in a calm sea are thought to presage wind from that way they come; and if they play and throw up water when the sea is rough, they presage fair weather; and most kinds of fishes swimming on the top of the water, and sometimes leaping, do prognosticate wind.

Upon the approach of wind, swine will be so terrified and disturbed, and use such strange actions, that country people say that creature only can see the wind and perceive the horridness of it.

A little before the wind, spiders work and spin carefully, as if they prudently forestalled the time, knowing that in windy weather they cannot work.

Before rain the sound of bells is heard further off, but before wind it is heard more unequally, drawing near and going further off, as it doth when the wind blows really.

Pliny affirms for a certain that three-leaved grass creeps together, and raises its leaves against a storm.

He says likewise, that vessels which food is put into will leave a kind of sweat in cupboards, which presage cruel

storms.

There lies hidden a flatuous and expansive spirit in quicksilver, so that it doth (in some men's opinions) imitate gunpowder and a little of it mixed with gunpowder will make the powder stronger. Likewise the chymists speak the same of gold, that being prepared some way, it will break out dangerously, like to thunder; but these things I never tried.

As originally published the History of the Winds' had appended to it the Aditus, or Introduction, to the other five enumerated Histories. The second History, or that of Density and Levity, was after Bacon's death published from his papers, first by Gruter (1653), among the Impetus Philosophici (pp. 337-379), and secondly in a more perfect form by Rawley in the Opuscula Varia Posthuma (1658). That History, therefore, now follows the History of the Winds.' We believe the only English translation of the Historia Densi et Rari' is that inserted by Shaw in the Fourth Part of his arrangement of the Instauration, and entitled by him 'A Plan for the Particular History of Condensation and Rarefaction in Natural Bodies.' The following is Shaw's version of the Aditus, or Introduction :

:

No wonder if nature remain debtor to philosophy and the sciences, when she has never been summoned to an account; for there has hitherto been no careful and regular inquiry, no exact or tolerable estimate made, as to the sum or quantity of matter in nature; nor any notice taken how it is disposed and laid out upon bodies. It is a just axiom that nothing can be detracted from or added to the sum total of the universe; and some indeed have handled the common-place, how bodies may be relaxed and contracted, in respect of more and less, without admitting a vacuum between: but for the nature of condensation and rarefaction, one attributes it to a greater and less quantity of matter; another eludes the point; whilst the generality following their author, think to discuss and settle the whole matter by that trifling distinction of art and power. And even they who attribute condensation and rarefaction to the different quantities of matter, which is the true notion, and do not totally deprive the materia prima of quantity; though for other forms they require it to be indifferent, yet here end their inquiry, and look no farther without perceiving the consequence: thus slightly passing over, or at best not fully pursuing a consideration which regards infinite particulars, and is in a manner the foundation of all natural philosophy.

To proceed, therefore, upon what has been justly laid down in all the transmutation of bodies; matter can never be aunihilated, but it requires the same omnipotent power to annihilate as to create out of nothing; neither of which ever happens in the course of nature, so that the original quantity of matter remains still the same, without addition or diminution. And that this original stock of matter is differently portioned out among bodies cannot be doubted; for it were madness, by abstract subtilties, to pretend that one hogshead contains as much water as ten hogsheads of water; or, that one hogshead of air contains as much as ten hogsheads of air. But though it be admitted that the quantity of matter rises in proportion to measure in the same body, this is still questioned in bodies of different kinds but if it be demonstrated that one hogshead of water turned into air will make ten hogsheads of air (and it may rather be proved to make a hundred), there is an end of the dispute, for in this case the water and the air are the same body, now contained in ten hogsheads, though before it was contained in one and therefore to assert that one whole hogshead of water may be couverted into but one whole hogshead of air, is in effect to assert that something may be reduced to nothing;

for in this case one-tenth part of the water is sufficient, and the other nine parts must then be annihilated: so, on the contrary, to assert that a hogshead of air is convertible into a hogshead of water, is to assert that something may be created out of nothing; for the hogshead of air will make but the tenth part of a hogshead of water, and therefore the other nine parts must be produced from nothing.

We shall, however, ingenuously confess it a difficult task to settle and ascertain the exact proportions and quantities of matter contained in different bodies, and to show by what industry and sagacity a true information may be had thereof; though the great and extensive usefulness of the inquiry may abundantly reward the pains that shall be bestowed upon it: for to understand the density and the rarity of bodies, and much more how to procure and effect their condensation and rarefaction, is a thing of the utmost importance, both in speculative and practical philosophy; therefore as the inquiry is, perhaps, of all others the most fundamental and universal, we should come to it well prepared, for all natural philosophy is a perfectly loose and untwisted thing without it.

This History, it therefore appears, is in reality mainly an inquiry into what is now called the specific gravity, or, as Bacon terins it, the comparative gravity (gravitas comparata), of different substances. Instead of distilled water, which is now commonly employed as the standard of comparison, he adopts pure gold as his standard. But his tables of specific gravities, if they were narrowly examined, would probably be found to exhibit much more serious discordances with the results of modern investigation than this. Bacon himself, however, distinguishes density and rarity throughout from gravity and levity, venturing to affirm only that the latter qualities appear to have a general consent or agreement with the former. And he had also, as we have seen, proposed a separate History of Gravity and Levity. Much of the present investigation, besides, is occupied with the subject of heat and cold.

The History of Density and Rarity' shows all Bacon's wonted activity and patience in the collection of facts, and also considerable ingenuity in many of the experiments which are detailed or suggested; though it would

be difficult to detect in the conduct of the inquiry the regular application either of what he has propounded in the Novum Organum as his own novel method, or of any other. But it does not contain many things that are now of much interest in any point of view. The following extracts from Shaw's version will afford a sufficient specimen of the work :

We know of nothing heavier than pure gold; nor has any method yet been found of increasing the gravity of pure gold by art.

But lead has been observed to increase both in bulk and weight; especially by lying in cellars underground, where bodies readily grow mouldy. This has principally been observed in stone statues; the feet whereof, where fastened together with bands of lead, that have been found swelled so that some parts thereof hung prominent or pendulous, like warts upon the stone. But whether this were really an increase of the lead or only a sprouting of its vitriol, should be farther examined.

Having once, by accident, left a cut citron in a parlour for two months in the summer, I afterwards found a sprouted putrefaction on the part that was cut, appearing to rise in certain hairs, the height of an inch; and on the top of each hair grew a head like the head of a small iron nail, thus plainly beginning to resemble a plant.

Air is simply dilated by heat; for in this case there is nothing separated or emitted, as in tangible bodies; but barely an expansion made.

In the case of cupping-glasses, when the glass and the air it contains are heated, the glass is applied to the skin; and soon after the air which was dilated by the heat, gradually contracts itself as the heat decreases, upon which the flesh is thrust into the glass by the motion of connexion. If it be desired that the cupping-glass should draw stronger, let a sponge be dipped in cold water and applied to the belly of the glass; for by this coolness the internal air will be more contracted, and the attraction of the glass increased.

If a glass be heated and inverted into water, it will attract the water, so as to fill a third part of the cavity; whence it is plain that the air was rarefied by the heat in that proportion. But if instead of a thin glass, which will not bear a great heat without danger of breaking, an iron or copper vessel were

employed and heated to a greater degree, we judge that air might be dilated above twice or thrice more, which is an experiment very well worth trying; as likewise to ascertain the degree whereto the air may be rarefied, that we may the better judge of its degree of rarefaction in the upper regions, and thence of the ether itself.

It appears very plain from the thermometer, that a small increase of heat may prodigiously expand the air, so that the hand laid upon the glass, a few rays of the sun, or even the breath of the bystanders, shall affect it; nay, the tendencies of the external air to cold and heat, though imperceptible to the touch, do yet constantly dilate and contract the air in the glass.

Hero describes an altar built so artificially, that when the offering is lit up thereon, water shall of a sudden descend and put out the fire. No other contrivance is requisite to this purpose than to leave a close hollow space under the altar, filled with air, which being heated by the fire, and consequently dilated, shall find no exit but through a pipe rising along the wall of the altar; and having its mouth bent down at last so as to discharge upon the altar. This upright pipe was filled with water, and had a belly in the middle that it might contain the larger quantity, and a stop-cock at the bottom to prevent the water from falling through; which stopcock being turned, admitted the dilated air to rise up and drive out the water.

It was the invention of Fracastorius to recover persons from apoplectic fits, by applying a heated metalline pan, at some distance, round the patient's head, in order to dilate, excite, and revive the spirits stagnating, congealed, or blocked up by the humours in the cells of the brain.

Bullets likewise shot from a gun, after their projectile motion entirely ceases, so as that to the eye they shall seem perfectly at rest, yet a great shuddering motion or pulsation will be found in their small parts for a long while after; insomuch that if any proper matter be laid upon them it will thence receive and manifest a considerable force; and this proceeds not so much from the burning heat as from the tremor of percussion.

Rods of wood being fresh gathered and kept turning in hot embers, acquire a softness, whence they may be bent at pleasure and this experiment should be tried in old rods and canes.