wings of flies, the slough of snakes, and also various artificial productions, as tender rose-leaves remaining after distillation, and the like, are (as I conceive) lighter than the lightest woods.

5. That idea to which the human mind is prone, namely, that hard bodies are the densest, is to be checked and corrected. For quicksilver is a fluid, gold and lead are soft; yet these are denser and heavier than the hardest metals (iron and brass), and much more so than stones.

6. In the Table there are many unexpected results. For instance, that metals are so much heavier than stones; that glass (a refined body) is heavier than crystal (a congealed body); that common earth has so little weight; that the distilled oils of vitriol and sulphur are nearly as heavy as the raw substances; that there is so little difference between the weight of water and wine; that chemical oils (which would seem to be more fine and subtle) are heavier than expressed oils; that bone is so much heavier than horn and teeth; and many other things of a similar character.

Injunction. 3. The nature of Dense and Rare, though it pervades nearly all other natures without being subject to their laws, appears only to have a great agreement with Heavy and Light. But I suspect that it has likewise something in common with the slow and quick reception and rejection of heat and cold. Make experiment therefore

whether rare bodies do not admit and lose heat or cold more

quickly than dense ones. And try this in gold, lead, stone, wood, and the like; but do it with the same degree of heat, and with the same quantity, and figure of body.

Reminders concerning Practice.

1. All mixture of bodies may be detected and disclosed by means of the Table and Weights. For if you wish to find how much water is mixed with wine, or how much lead with gold, and the like; weigh the mixture, and then consult the Table of specific gravities. The mean proportion of the compound compared with the simples will give the quantity of the mixture. I suppose this was the ɛűρŋка of Archimedes; but at any rate the thing is so.

2. The manufacture of gold, or the transmutation of metals into gold, is to be much doubted of. For of all bodies gold

is the heaviest and densest, and therefore to turn anything else into gold there must needs be condensation. But condensation (especially in very materiate bodies, as metals are) can scarce be superinduced by us men who live on the surface of the earth. For most condensations by fire are pseudocondensations with respect to the entire body (as will afterwards appear); that is, they condense bodies in certain of their parts, but not in the whole.

3. But the conversion of quicksilver or lead into silver (which is rarer than either of them) is a thing to be hoped for; since it only implies fixation, and some other things, but not condensation.

4. Notwithstanding if quicksilver, lead, or any other metal could be turned into gold, so far as to have all the other properties thereof except weight; that is, if they could be made more fixed, more malleable, more ductile, more durable, less subject to rust, brighter, yellower, and the like; it would doubtless be both profitable and useful, even though they did not acquire the weight of gold.

Observation.

7. There is nothing heavier than gold; and up to this time no invention has been discovered to make pure gold heavier by art.

It has been remarked however that lead increases both in bulk and weight, especially if it be stored in cellars under ground, where things soon gather rust. This has been principally detected in stone statues, whose feet were fastened with leaden bands. For these bands have been found to swell; so that portions of them hung from the stones like warts. But whether this were an increase of the lead, or a sprouting of vitriol, should be more fully inquired.

The History.

A TABLE OF THE BULK OF MATTER WITHIN A GIVEN SPACE OR DIMENSION IN THE SAME BODIES WHOLE AND POWDERED.

A TABLE OF THE BULK OF MATTER WITHIN A GIVEN SPACE OR DIMENSION, IN BODIES CRUDE AND IN BODIES

DISTILLED.

Admonition. The manner of converting a body into powder conduces much to the opening or expansion of the body. For the process by simple rubbing or filing is one thing, that by sublimation, as in mercury, another; that by strong waters and corrosives (that is by turning the bodies into rust) as in oxide of iron, and slightly in prepared steel, another; and that by burning, as ashes and lime, another. Therefore these are by no means to be regarded as the

same.

Injunction.

These two Tables are extremely meagre. That would be a perfect table of bodies with their openings, which should give first the weight of every body in its whole state; secondly, that of its crude powder; thirdly, that of its ashes, calcination, and rust; fourthly, that of its amalgamations; fifthly, that of its vitrifications (if it is vitrifiable); sixthly, that of its distillations (subtracting the weight of the water wherein it is dissolved), with all the other alterations of the same body; that so a judgment might be formed of the openings of bodies, and the closest connections of integral nature.

Observations.

1. Powders are not properly openings of bodies, because the increase of space is not caused by dilatation of the body, but by interposition of air; yet an excellent estimate of the internal closeness or porosity of bodies is obtained thereby.

For the closer bodies are, the greater is the difference between their powder and their body entire. Therefore the proportion of crude quicksilver to sublimate of mercury in powder is as five to one, or rather more. The proportions of steel and lead are not quite so much as four to one. But in lighter and porous bodies the position of the parts is sometimes looser in the entire body than in its powder when compressed; as in oak wood, the ashes are heavier than the body itself. So likewise in the powders themselves, the heavier a body is the less dimension has the powder when pressed, compared with the same unpressed. For in lighter bodies the parts of the powders (as they less compress and cut the air that is mixed with them) can so support themselves that the powder unpressed will fill three times as much space as when pressed.

2. Distilled bodies are generally rarefied, and lose in weight; but wine does this twice as much as vinegar.

Speculation.

1. Tangible bodies have thus been divided into classes of rich and poor. There remains still another class, namely, that of pneumatic bodies; but these are not indued with weight, the effect of which would enable us to form a judgment of the bulk of matter contained in them. We require therefore another kind of interpreter. But first I must set forth the kinds of pneumatic bodies, and then proceed to compare them.

As in tangible bodies I postpone for a while the inquiry of the internal parts of the earth, so in pneumatic bodies I postpone speaking of things eternal.

Pneumatic bodies with us are of three kinds; imperfect,. attached, and pure. The imperfect are fumes of all kinds, and arise from different matters; which may stand in this order. First, volatile fumes, that exhale from metals and some fossils, which (as their name signifies) are rather volatile than pneumatic; because they are very easily coagulated, either by sublimation or by falling or precipitation. Secondly, vaporous fumes that exhale from water and watery bodies. Thirdly, fumes (using the general name in a special sense) that exhale from dry bodies. Fourthly, exhalations from oily bodies. Fifthly, breaths from bodies watery in their substance and inflammable in their spirit; as are wines, fermented liquors, and strong drinks.

There is likewise another kind of fumes; namely, those in which flame terminates. But these can only exhale from inflammable bodies, as they succeed flame. These I call afterfumes or secondary fumes. Therefore there can be no aftervapours, because watery bodies are not inflammable; but there may be after-fumes (using the word in the special sense), afterexhalations, after-breaths, and likewise, as I conceive, in some bodies, after-volatiles.

Attached pneumatic bodies are those which are not found by themselves or free, but only inclosed in tangible bodies; and are the same as what are commonly called spirits. They partake both of an oily and a watery substance, and are nourished by the same; which, on being.converted into a pneumatical substance, constitute a body composed as it were of air and flame, and combining the mysterious properties of both. Now these spirits (in the case of free pneumatic bodies) approach very nearly to the nature of breaths; such as rise from wine or salt. They have two natures; the one of crude, the other of living spirits; whereof the former exist in every tangible body, the latter only in such as are animated, whether of the vegetable or sensitive world.

Of pure pneumatic bodies there are only two; namely, air and flame; though these also admit of great variety, and unequal degrees of bulk.

A TABLE OF PNEUMATIC BODIES ACCORDING TO THE FOREGOING SPECULATION, ARRANGED IN ORDER OF BULK.

We are now to inquire of the bulk of these bodies as compared with one another, and also with tangible bodies. And if the nature of lightness could by its tendency upwards make manifest the rarity of bodies, as the nature of heaviness by its tendency downwards makes manifest their density, the comparison might well be made. But there are many difficulties in the way.

First, the differences of motions in invisible bodies are not