and cold. We would, therefore, have trial made, whether rare bodies do not grow hot and cold, quicker than dense ones. The experiment should be performed on gold, lead, stone, wood, &c. with the same degree of heat, the same quantity, and the same figure of the body.*

PRACTICAL HINTS.

All the mixtures of bodies may be discovered by means of an exact table of specific gravities, and the test of weight. Thus to find what proportion of water is mixed with wine; lead, with gold, &c. the mixture being weighed, and the table consulted, for the respective weights of the simples; the mean proportion of the compound, compared with the simples, will give the quantity of the mixture. And this we judge was the method used by Archimedes, in detecting the debasement of king Hiero's crown.

The making of artificial gold, or the transmutation of metals into gold, should be held suspect; for gold is the heaviest and densest of all bodies; and therefore to convert any thing else into it, is absolutely the work of condensation: but condensation can scarce be super-induced by

+ There are some experiments to this purpose in Boerhaave's Chemistry; particularly in the Chapter of Fire.

men upon the surface of the earth; especially in bodies that are full of matter as metals are. For most condensations effected by fire, are false, or imperfect condensations, with regard to the whole; and only condense bodies in certain parts, as we shall see hereafter.

3. But the conversion of quicksilver, or lead, into silver, which is a rarer body than either, may rationally be hoped for: as requiring only fixation, not condensation.

4. Yet if quicksilver, lead, or any other metal, could be turned into gold, in all other properties except gravity; or be rendered more fixed, more malleable, soft ductile, durable, bright, yellow; or less subject to tarnish; it may doubtless prove an useful and gainful operation.

A LARGER OBSERVATION,

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

HISTORY.

But lead has been observed to increase both in bulk and weight; especially by lying in cellars under ground, where bodies readily grow mouldy. This has principally been observed

*The gravity of silver is said to have been considerably increased.

in stone statues; the feet whereof when 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.*

A Table, shewing the different expansion of Bodies whole and in powder.

* See Mr. Boyle's works, abridgm. vol. iii.

ADMONITION.

The manner of reducing a body to powder, contributes greatly to the opening, rarifying, or expanding of that body. But the reduction of a body to powder by simple triture, or by filing, is one thing; by chemical sublimation another; by corrosion with acid spirits, another; and by calcination, another, so as to have very different effects.

PRECEPT.

These two tables are extremely scanty and defective; but that would be an exact and copious one of bodies and their expansions, which in the first column contained the weight of each body; in the second the weight of its crude ⚫ powder; in the third, that of its ashes, calx, or rust; in the fourth, that of its pappy mass; in the fifth, that of its vitrification, if it be vitrifiable; in the sixth, its matter by distillation; in the seventh that of its solution, subducting the weight of liquor that dissolves it; and so on, till it exhibits the weights of the same body under all its changes, and other alterations: from which table a judgment might be formed of the relaxations of bodies, and the closest integral connexions of nature.

OBSERVATIONS.

Pulverization is not properly a rarifaction of the body pulverized; because the increase of

bulk proceeds not from the dilatation of the body; but from the interposition of air: yet an estimate of the internal connexion or porosity of bodies may be excellently derived from it. For the closer bodies unite, the greater difference there is between their powder and entire body; and therefore quicksilver is to mercury-sublimate in powder, as above five to one; and the proportions of steel and lead to prepared steel, and ceruse in powder, are not so much as four to one. But in the lighter and more porous bodies, there is sometimes a looser position of parts, in the wholes, than in the pressed powders; so the ashes of oak-wood are heavier than oak itself. And again, in powders, the heavier the entire body is, the less dimension its squeezed powder has, in comparison of another unsqueezed for in light bodies the parts of powders may sustain or support themselves; so that an unsqueezed powder shall possess thrice the space of a squeezed one; on account of its less condensing, and dividing the air interposed betwixt its parts.

2. Distilled bodies are generally rarified, and made light, by the operation; but wine twice more than vinegar.

A speculation for practice.

And thus tangible bodies may be reduced under classes, according to their families; or as