246. 3. Air absorbs Water, and Water absorbs Air:[63] and the Absorption of Air by Water is promoted by Agitation: it also absorbs twice as much defloguisticated Air, as common Air:[64] the whole Bulk of the Air absorbed being equal to one-twelfth of the Bulk of the Water: yet the Bulk of the Water seems but little encreased: the Air being contained within the Interstices of the Water.
247. The following is a pretty and an easy Experiment, to shew how the absorption of water by air takes Place, under the immediate Inspection of the Observer.
Admitting the Sun’s Light into a Room, throu’ one Window only; pour a Pint of boiling Water into a large Bason: hold the Bason, which will not be half full, next the Light, in such a Manner, that the Sun may shine on the Water and Bason; yet the Eyes be shaded by the Top of the Window Frame.
Incline the Side of the Bason towards the Light, so that the Water may rise even with the Top.
The Eye being placed just above the upper Side of the Bason, farthest from the Light; look on the Water.
You may then observe the Surface of the Water next the Light, refract the Sun’s Rays, and produce the primary Colours, particularly the red and green: which tho’ transient, continue to be seen in Succession; as Vapours rise above the Surface of the Water. Their first Ascent is plainly discoverable: remaining above its Surface, in the Form of small Dust, gently agitated, not separately but as a whole. Nor do they seem to rise into Steam, till assisted by the Action, and Contact of dry Air, which like dry Spunges, licks off and absorbs the small Dust already accumulated by the Force of the Heat from below, and then becomes visible under the Appearance of Steam, flying off in distinct hollow Vesicles.
The more still the Air of the Room, the more slowly will the Spunges of Air come in Contact with the Body of small Dust.—Besides the small Dust already mentioned; the Heat will detach solid Globules of Water; which will remain floating on the Surface of the Body of Water: till the dry Air descends and transports them with it; the Air at the same Instant dissolving the solid Globules into hollow Vesicles.
But the most extraordinary Phenomenon, and which cannot be mistaken, is, that as soon as a Spunge of Air has dipped into the Surface of Water, and received its Lading; the Vesicles continue to accumulate, till another fresh Spunge descends in a similar Form, which may be traced upon the Surface of the Water, and seen in its Shadow, or rather in Beams of Light at the Bottom of the Bason, at the Instant it has flown off with its Burden: for that Part of the Surface of the Water transmits new Rays of Light, on Removal of the Vapour carried away by the Dip and Play of Air.
248. The Removal of the Vapour, likewise exhibits a curious Appearance on the Surface of the Water: which seems as if divided into irregular Parcels detached from each other; like the reticular Daplings visible on the under Side of Clouds elevated to the highest Stratum of the Atmosphere, and there evaporating or dissolving.
249. So powerful is the Attraction between Air and Water; that, while the Steam is rising above and round the Sides of the Bason; Waves of fresh Air, by Intervals, press the exterior Parts of the Steam inwards, in order to get at the Surface by descending into the Bason.