air; whereas it certainly has that effect upon the spirits contained in the parts of animals: which is manifest from the secondary qualities of me-dicines. But of this let farther enquiry be made; according to the following precept.

PRECEPT.

Take two weather-glasses, of the same size fill the one with water, and the other with rectified spirit of wine; heat the glasses in such a manner, that both the water and the spirit may stand at the same height; then place them together, leave them a time, and observe if the water stand higher than the spirit: for if it does, it is plain that the potential heat of the spirit of wine expands the air, so as to depress the spirit*.

It might be very useful, sometimes to try and exercise the operations of the secondary medicinal qualities in lifeless bodies. For although no effect could be expected from most of them; as a living spirit is absolutely required to actuate them, on account of the subtilty of the operation; yet others of them would have an opera

The difference may proceed from the spirit of wine being more rarifiable by the warmth of the external air, than water; but whether rarifaction be the form of heat is not hitherto satisfactorily determined. See the Novum Organum; part ii. aph. 12, &c.

5

tion upon some inanimate bodies. Thus, we see what effect salt has upon flesh, spices upon dead carcasses, rennet upon milk, leaven upon bread, &c. The diligence therefore of physicians, as to their secondary qualities, may, if judiciously considered and transferred, serve in performing numerous other operations: always supposing that a stronger virtue is required to operate upon a dead body than a live one.*

SECT. VIII.

THE HISTORY OF DILATATION' IN BODIES BY A RELEASF-MENT OF THEIR SPIRIT.

TRANSITION.

WE come next to the dilatations of bodies made by a releasement of their spirits, upon breaking the prison of the grosser parts, which closely detained them, so that they could not dilate for in bodies which have a compact closeness and remain strongly bound together in their wholes, the spirits cannot perform their office of dilating; unless there be first a solution of continuity in the grosser parts, made either by cor

The proper use seems not hitherto made of this precept.

rosive liquors, with or without the assistance of heat and this appears in the opening and dissolving of metals.

1. A penny-weight of pure gold may be reduced by the hammer, into thin plates: so as to be readily torn betwixt the fingers.

2. If the gold be now put into a glass, with four times its quantity of aqua regia, and the glass be set over a very soft and gentle fire; there will soon appear to arise therein certain little grains, which, after a small continuance, diffuse themselves and incorporate with the liquor; so as to render it bright and shining; as if tinged with saffron. But the gold, in the proportions here set down, dissolves only to a third; for the menstruum will imbibe no more: so that if the whole penny-weight of gold were to be dissolved, the saturated menstruum must be poured off; and again four penny-weight of aqua regia poured on; and so for the third time. This dissolution proceeds calmly, and slowly, in a moderate heat, without fumes, and without heating the glass, more than what the fire occasions.

3. To a quantity of crude quicksilver, put into a glass, add twice its weight of aqua fortis; and without setting the vessel to the fire, there will presently rise up something like a very fine powder, in the body of the liquor; and in the

ал

cl

D

b

space of an hour, without fire, without fumes, and without tumult, the mixture will appear a clear uniform liquor.

4. Put a penny-weight of thin plated lead to nine penny-weight of aqua fortis the lead will not here incorporate so well as the other metals; but the menstruum throws down the greater part of the lead, in form of a calx, to the bottom; the liquor above, remaining somewhat turbid, though tending to transparency.

5. To a penny-weight of plated silver, add four penny-weight of aqua-fortis; set them in a gentle heat and the silver will rise within the body of the liquor, like small sand, or bubbles, a little larger than those of gold; and incorporate with the menstruum, and turn with it into a thin, white, and as it were, milky liquor: but after standing and cooling for a while, icy plates appear to shoot in the body of it, proceeding from the mixture of the metal and the menstruum: but when, after a longer stay, the separation is totally made, the liquor becomes clear and crystalline; throwing the icy plates to the bottom. The menstruum here sustains the full weight of the metal; as in gold; and the dissolution is made almost with the like heat; and does not increase it by motion, any more than in the case of gold.

6. Six penny-weight of aqua-fortis being put to one penny-weight of copper-filings, and set in a sand-heat; the copper rises in larger grains, or bubbles, than silver; and soon after incorporates with the menstruum into a blue turbid liquor; but upon standing, it brightens up, like the sky, into a shining beautiful blue; throwing down the fæces, in form of powder, to the bottom; which fæces, however, are diminished in time, and ascend and incorporate with the rest and thus six penny-weight of aqua-fortis dissolves one penny-weight of copper, entirely; so that the menstruum here suffers itself to be charged with twice the weight it did in the case of gold and silver. But the solution of copper conceives a manifest heat, by the internal conflict, even before it is applied to the fire.

7. Three penny-weight of aqua fortis being added to one penny-weight of tin-filings, the whole metal is turned into a body like cream or curds, which does not readily clarify itself; but conceives a manifest heat without fire.

8. Nine penny-weight of aqua-fortis being poured upon one of iron-filings, the metal, without heat, rises up in large bubbles; not only within the body of the liquor, but above it; so as to boil out at the mouth of the glass.: at the same time emitting a copious, dense and saffron