fying, partly contracting; so that those contrary actions of fire, which are commonly observed,

As the same fire which makes the soft clay hard

Makes hard wax soft,1

are based on this; that in the one the spirit is emitted, in the other it is detained.

The condensation which is caused by fire, though not a pseudo-condensation (for it is substantial), is yet rather a condensation of the parts than of the whole. For certainly the grosser parts are contracted; yet so that the whole body is rendered more hollow and porous, and of less weight.

Provisional Rules.

1. The sum of matter in the universe is always the same; and there is no operation either from nothing or to nothing.

2. Of this matter there is more in some bodies, less in others, in the same space.

3. Abundance and scarcity of matter constitute the notions of dense and rare, rightly understood.

4. There is a limit of dense and rare which cannot be passed, but not in any body known to us.

5. There is no vacuum in nature, either collected or interspersed.

6. Within the bounds of dense and rare there is a fold of matter, by which it folds and unfolds itself without creating a vacuum.

7. The differences of dense and rare in known tangible bodies do not much exceed the proportions of 32 to 1.

1 Virg. Eclog. viii. 80.:

Limus ut hic durescit, et hæc ut cera liquescit,
Uno eodemque igni.

8. The difference between the rarest tangible body and the densest pneumatic body is 100 to 1, and more. 9. Flame is rarer than air, oil than water.

10. Flame is not rarefied air, nor oil rarefied water; but they are plainly heterogeneous bodies, and not very friendly.

11. The spirits of vegetables and animals are breaths compounded of an airy and flamy pneumatic body, as their juices are of one watery and oily.

12. Every tangible body with us has a pneumatic body or spirit united and inclosed within it.

13. Spiríts, such as those of vegetables and animals, are not found at large with us, but attached and confined in the tangible body.

14. Dense and rare are the proper effects of heat and cold; dense of heat, rare of cold.

15. Heat operates on pneumatic bodies by simple expansion.

16. Heat in a tangible body performs two operations; the pneumatic part it always dilates, but the gross part it sometimes contracts, sometimes relaxes.

17. Now the rule thereof is this; the emission of the spirit contracts and indurates the body; the detention of the spirit intenerates and melts it.

18. Colliquation commences with the expansion of the pneumatic part in the body; but other dissolutions commence with the expansion of the gross part, setting at liberty the operation of the pneumatic.

19. Next to heat and cold, the most powerful agents for rarefaction and condensation are the agreement and flight of bodies.

20. Restoration after violence both dilates and condenses in opposition to the violence.

21. Assimilation both dilates and condenses, according as the thing assimilating is rarer or denser than the thing assimilated.

22. The rarer bodies are, the greater is both the dilatation and contraction they submit to from external violence, within certain limits.

23. If the tension or pressure of a rare body exceed the bounds of endurance, rare bodies free and restore themselves more forcibly than dense ones, because they are more active.

24. The most powerful expansion is that of air and flame united.

25. Dilatations and contractions are imperfect when restoration is easy and at hand.

26. Dense and rare have a close connection with heavy and light.

27. Man is scantily supplied with the means of condensation, by reason of the want of potent cold.

28. Age is like a lambent fire, and performs the work of heat, but more finely.

29. Age brings bodies either to putrefaction or dry

ness.

Desiderata with their nearest Approximations. 1. Conversion of air into water.

Approximations. Springs in the hollows of mountains. Exudation of stones. Dew formed by the breath. The fleece upon the sides of ships (?). Watery meteors, and the like.

2. Increase of weight in metals.

Approximations. Conversion of iron into copper. Increase of lead in cellars (?). Conversion of quicksilver into gold (?).

3. Petrifaction of earth and other vegetable or animal substances.

Approximations. Petrifying water. Stones made up of an incrustation of small pebbles. Crystal icicles in caves. Stones in the kidneys, bladder, and gallbladder. Scales of teeth.

4. Various uses of the motion of dilatation and contraction in the air by heat.

Approximations. The thermometer. Hero's altar. The musical instrument played by the rays of the The device for imitating the ebb and flow of the sea and rivers.

sun.

5. Inteneration of the members of animals by a proportionate heat and detention of the spirit.

Approximations. Softening of iron. Softening of wax. All amalgamations. This pertains to the renewal of youth; for all moistening besides that performed by the detention of the native spirit seems to be a pseudo-inteneration, and of little effect; as we shall see under its own title.

Admonition.

Under this title I propose few desiderata and reminders about practice; for the matter is so general and extensive, that it is more adapted to inform the judgment than to instruct practice.