Air [...]
is generally understood to be that Fluid in which we breathe and the Earth is enclosed, and as it were wrapped up.
Air is found to have these Six Properties, following.
1. It is liquid, and cannot be congeal’d like Water.
2. It is mich lighter than Water, but yet is not without its Gravity.
3. It is diaphanous, that is, it transmits the Light.
4. It can easily be condens’d and rarefied.
5. It has an elastick Force.
6. It is necessary for Flame and Respiration.
I. It is much more liquid than Water is, and cannot be congeal’d, and that for the Reasons following.
1. Because it seems to have Pores much larger, full of finer Matter, of a very quick Motion, whereby the Particles of Air are continually driven about, as it appears by this Experiment, that if Air be pent up in a Vessel it is easily condens’d; whereas no Person yet, by any Invention, has been able to condense Water.
2. The Particles of Air are very fine and branched, so that they have Interstices between one another, and can never be formed into a compact Body.
II. Water had been prov’d by Experiment to be 840 Times heavier than Air, from whence it will follow, that a certain Bulk of Air contains in it 840 Times less homogeneous Matter than an equal Bulk of Water does; and this is the Reason why Air may be condens’d, but not Water.
III. The Air is Diaphonous, because having very wide Pores, and separable parts, it admits the Matter whereof Light consists through right Lines. And hence it is, tht not only the Sun and the Planets shine or reflect their Light upon us, but also the fixt Stars are seen by us at an immense Distance. But as deep Water does not tranmit all the Rays which fall upon it, because the Series of Light is interrupted by the Motion of the watery Particles: So many of the Rays, which fall upon this prodigious Bulk of Air over us, must needs be broken off and intercepted before they reach us; which probably may be the Cause, that where the Sky is very clear, it is not quite transparent, but appears of a more blue and waterish Colour.
IV. Air is condensed and rarefied, because it consisting of branchy Particles, those Particles are easily scatter’d by an extra-ordinary quick Motion, which is called Rarefaction.
Again, they are easily thrust into a less Compass, while their Branches are driven together, and close one with another, and thereby crush out the liquid Matter which lay between them; and this is called Condensation.
There are a Multitude of Experiments to prove this; as there are a sort of Guns, into which such a Quantity of Air may be forc’d, as to shoot out a Leaden Bullet with great Violence.
V. That the Air has an Elastick Force; that is, that it has a Power to return to the same State, and re-occupy the same Space which it filled before, when ever the Force that crushed it into a narrower Compass is removed, the beforementioned Experiment does demonstrate.
VI. That Air is necessary forFlame or Respiration. Without Air, Flame and Fire go out, and Air seems to have a nitrous or sulphurous Matter in it, that the Air which lies upon so many Plants, Animals and Minerals, upon which the Heat of the Sun continually operates and extracts a good Part of them, must needs carry away with it innumerable Particles of Sulphur and volatile Salts, wherewith Things abound, as chymical Experiments demonstrates.
Air is represented by a Damsel sitting upon a Cloud with her Hair dishevel’d, and a loose, flying Garment, with one Hand stroking a Peacock, and holding under her other Arm a Cameleon. All sorts of Birds flying round a bout her. Plate I. Fig. 11.
Pure Air is represented by a Lady of a serene and beautiful Aspect, cloth’d in Gold: holding in one Hand a white dove, the other holding up Zephyrus or the West Wind in the clouds with this motto: Spirat levis aura Favoni. See Plate I. Fig. 12.
This intimates the West Wind to be the most Healthful. The white dove is an Emblem of Health, being an Antidote against Infection. Her Aspect and Gold Habit denote the same.

Definition taken from The Universal Etymological English Dictionary, edited by Nathan Bailey (1736)

Aiguisce, or Eiguisce [in Heraldry] * Air [in Chymical Writers]
Aˊcto [Old Records]
Adoˊlescence, or Ado’lescency
Adventitious Glandules [Anatomy]
Adventitious Matter [with Philosophers]
Æˊgilops [in Surgury]
Aiguiˊsce, or Aigui’sse, or Agui’sse [in Heraldry]
Aiguisce, or Eiguisce [in Heraldry]
Air [in Chymical Writers]
Air [in Horsemanship]
Aˊiriness [of Air]
High Airs
Air [with Anatomists]
Air [with Musicians]
To Air
Air pump
Airy Meteors [with Astronomers]
Airy Triplicity [with Astrologers]