[] Some have objected against the Distribution of the Earth and Waters, as if the Waters occupied too large a part of the Globe, which they think would be of greater Use, if it was dry Land. But then they do not consider that this would deprive the World of a due Quantity of Vapours and Rain. For if the Cavities which contain the Sea, and other Waters, were deeper, although the Waters were no less in Quantity, only their Surfaces narrower and lesser, the Evaporations would be so much the less, inasmuch as those Evaporations are made from the Surface, and are, consequently, in proportion to the Surface, not the Depth or Quantity of Water.
[c] I took notice before in [Book I. Chap. 3. Note (a).] That the Vapours constituting Clouds and Rain, are Vesiculæ of Water detached by Heat. The manner of which I conceive to be thus; Heat being of an agile Nature, or the lightest of all Bodies, easily breaks loose from them; and if they are humid, in its Passage, carries along with it Particles, or little Cases of the Water; which being lighter than Air, are buoyed up thereby, and swim in it; until by knocking against one another, or being thickened by the Cold, (as in the Note before-cited,) they are reduced into Clouds and Drops.
Having mentioned the manner how Vapours are raised, and there being more room here than in the Note before-cited, I shall, for the Illustration of Natures Process, take notice of three Things observable to our purpose, in Water over the Fire. 1. That the Evaporations are proportional to the Heat ascending out of the Water. A small Heat throws off but few Vapours, scarce visible: A greater Heat, and ascending in greater Quantities, carries off grosser, larger, and more numerous Vesiculæ, which we call a Steam: And if the Heat breaks through the Water with such a Fury, as to lacerate and lift up great Quantities or Bubbles of Water, too heavy for the Air to carry or buoy up, it causeth what we call Boyling. And the Particles of Water thus mounted up by the Heat, are visible Sphærules of Water, if viewed with a Microscope, as they swim about in a Ray of the Sun let into a dark Room, with warm Water underneath; where some of the Vapours appear large, some smaller Sphærules, according (no doubt) to the larger and lesser Quantities of Heat blowing them up and carrying them off. 2. If these Vapours be intercepted in their Ascent by any Context, especially cold Body, as Glass, Marble, &c. they are thereby reduced into Drops, and Masses of Water, like those of Rain, &c. 3. These Vapours in their Ascent from the Water, may be observed, in cold frosty Weather, either to rise but a little above the Water, and there to hang, or to glide on a little above its Surface: Or if the Weather be very cold, after a little ascent, they may be seen to fall back again into the Water; in their Ascent and Descent describing a Curve somewhat like that of an Arrow from a Bow. But in a warmer Air, and still, the Vapours ascend more nimbly and copiously, mounting up aloft, till they are out of Sight. But if the Air be warm and windy too, the Vapours are sooner carried out of Sight, and make way for others. And accordingly I have often observed, that hot Liquors, if not set too thin, and not frequently stirred, cool slower in the greatest Frosts, than in temperate Weather, especially if windy. And it is manifest by good Experiments, that the Evaporations are less at those times than these; less by far in the Winter than the warmer Months.
[c] As our Northern Islands are observed to be more temperate than our Continents, (of which we had a notable Instance in the great Frost in 1708/9, which Ireland and Scotland felt less of, than most Parts of Europe besides; of which see [Book IV. Chap. 12. Note (c).]) so this Temperature is owing to the warm Vapours afforded chiefly by the Sea, which by [the preceding Note] must necessarily be warm, as they are Vapours, or Water inflated by Heat.
The Cause of this Heat I take to be partly that of the Sun, and partly Subterraneous. That it is not wholly that of the Sun, is manifest from Vapours, being as, or more copiously raised when the Sun Beams are weakest, as when strongest, there being greater Rains and Winds at the one time than the other. And that there is such a thing as Subterraneous Heat, (whether Central, or from the meeting of Mineral Juices; or such as is Congenial or Connatural to our Globe, I have not Time to enquire; but I say, that such a Thing is,) is evident not only from the Hot-Baths, many fiery Erruptions and Explosions, &c. but also from the ordinary Warmth of Cellars and Places under Ground, which are not barely comparatively warm, but of sufficient Heat to raise Vapours also: As is manifest from the smoking of perennial Fountains in frosty Weather, and Water drawn out of Pumps and open Wells at such a Time. Yea, even Animals themselves are sensible of it, as particularly Moles, who dig before a Thaw, and against some other Alterations of the Weather; excited, no doubt, thereunto by the same warm Vapours arising in the Earth, which animate them, as well as produce the succeeding Changes of the Weather.
[d] Besides the Trade-Winds, which serve to mitigate the excessive Heats in the Torrid Zone; the Clouds are a good Screen against the scorching Sun-Beams, especially when the Sun passeth their Zenith; at which Time is their Winter, or coolest Season, by reason they have then most Clouds and Rain. For which Service, that which Varene takes notice of, is a great Providence of God, viz. Pleraque loca Zonæ Torridæ vicinum habent mare, ut India, Insulæ Indicæ, Lingua Africæ, Guinea, Brasilia, Peruvia, Mexicana, Hispania: Pauca loca Zonæ Torridæ sunt Mediterranea. Varenii. Geogr. l. 2. c. 26. Prop. 10. §. 7.
[e] That Springs have their Origine from the Sea, and not from Rains and Vapours, among many other strong Reasons, I conclude from the Perennity of divers Springs, which always afford the same quantity of Water. Of this sort there are many to be found every where. But I shall, for an Instance, single out one in the Parish of Upminster, where I live, as being very proper for my purpose, and one that I have had better Opportunities of making Remarks upon above twenty Years. This in the greatest Droughts is little, if at all diminished, that I could perceive by my Eye, although the Ponds all over the Country, and an adjoining Brook have been dry for many Months together; as particularly in the dry Summer Months of the Year 1705. And in the wettest Seasons, such as the Summer and other Months were, preceding the violent Storm in November 1703. (Vid. Philos. Trans. Nᵒ. 289.) I say, in such wet Seasons I have not observed any Increment of its Stream, excepting only for violent Rains falling therein, or running down from the higher Land into it; which discoloureth the Waters oftentimes, and makes an increase of only a Day’s, or sometimes but a few Hours Continuance. But now, if this Spring had its Origine from Rain and Vapours, there would be an increase and decrease of the one, as there should happen to be of the other: As actually it is in such temporary Springs as have undoubtedly their Source from Rain and Vapours.
But besides this, another considerable Thing in this Upminster Spring (and Thousands of others) is, that it breaks out of so inconsiderable an Hillock, or Eminence of Ground, that can have no more Influence in the Condensation of the Vapours, or stopping the Clouds, (which the Maintainers of this Hypothesis suppose) than the lower Lands about it have. By some Critical Observations I made with a very nice portable Barometer, I found that my House stands between 80 and 90 Feet higher than the Low-Water Mark in the River of Thames, nearest me; and that part of the River being scarce thirty Miles from the Sea, I guess, (and am more confirmed from some later Experiments I made nearer the Sea) that we cannot be much above 100 Feet above the Sea. The Spring I judge nearly level with, or but little higher than where my House stands; and the Lands from whence it immediately issues, I guess about 15 or 20 Feet higher than the Spring: and the Lands above that, of no very remarkable Height. And indeed, by actual Measure, one of the highest Hills I have met with in Essex, is but 363 Feet high; (Vid. Phil. Trans. Nᵒ. 313. p. 16.) and I guess by some very late Experiments I made, neither that, nor any other Land in Essex, to be above 400 Feet above the Sea. Now what is so inconsiderable a rise of Land to a perennial Condensation of Vapours, fit to maintain even so inconsiderable a Fountain, as what I have mentioned is? Or indeed the High-lands of the whole large County of Essex, to the maintaining of all its Fountains and Rivulets?
But I shall no farther prosecute this Argument, but refer to the late learned, curious and industrious Dr. Plot’s Tentamen Phil. de Orig. Font. in which he hath fully discussed this Matter.
As to the manner how the Waters are raised up into the Mountains and Higher Lands, an easy and natural Representation may be made of it, by putting a little Heap of Sand, Ashes, or a little Loaf of Bread, &c. in a Bason of Water; where the Sand will represent the dry Land, or an Island, and the Bason of Water the Sea about it. And as the Water in the Bason riseth to, or near the top of the Heap in it, so doth the Waters of the Sea, Lakes, &c. rise in the Hills. Which case I take to be the same with the ascent of Liquids in capillary Tubes, or between contiguous Planes, or in a Tube filled with Ashes: Of which the industrious and compleat Artificer in Air-Pumps, Mr. Hawksbee, hath given us some, not contemptible Experiments, in his Phys. Mech. Exp. pag. 139.