Internal Air lofe its Warmth, and become equally cold with the External. Now if the Bladder be tied close enough, the Expanfive Power of the Air, which is in the Bottle above the Water, will become weaker than that of the External, because the quantity of the Air is diminished, and is therefore more rarified: Wherefore in cafe the External Air, which is strongest, can operate against the other, it will be driven with a Current or Stream against the rarified Air; which may be discover'd by making a Hole in the Bladder with a Pin, whereupon you will immediately fee the External Air, like a Wind, rifing up thro' the Water.

Now, whether from all thefe Properties of the -Air, and from the Heat of the Sun operating thereupon, the Eafterly Trade-Winds, and in fome measure likewife, thofe that blow from the South in Spring and Summer, and from the North in Autumn and Winter, may be truly prov'd according to the manner of the Modern Naturalists: Those that are curious, may enquire by confulting them.

SECT. XXXVII. The Eleventh Experiment; Wind produced by the Motion of the Air upwards.

XI. THERE is ftill one other Motion and Current of the Air mention'd by Dr. Halley, in his Difcourfe about the Winds (See Philofoph. Tranfact. Numb. 183.) by which it acquires a Process upwards; namely, when the Air, being rarified by Warmth or otherwife grows thinner, and confequently lighter in the fame place than when it is compreffed and encreased by Cold (as it has been fhewn upon other Occafions;) it follows therefore, that in cafe the Warmth defcends perpendicularly from the Sun, there will be produced directly under it, a freight afcending Column in the Air, as far

as

as the great and defcending Heat extends it felf; in which Column the Air will be much lighter than that which is about it, and which has not fo much Heat. Now if we look upon this thinner Air as Oil, and the furrounding colder Air as Water, every Body must own, that as a Column of Oil placed in the middle of Water does emerge, or is driven upwards, and according to the Laws of Gravity, diffuses itself upon the Surface of the Water, the fame Appearances will likewife happen in this rarified Air. Dr. Halley ufes this Comparison, to give us fome kind of Notion, tho', as he owns himself, a very imperfect one, of the Motion of the Air in the Monfoons.

In order to fupport these Arguments by Experiments, and to render in fome manner vifible fuch a Current and Wind produced in the Air, take a little Glass, EF KL, (Tab. XIV. Fig. 7.) about fix Inches high, and the Mouth of it between two or three Inches broad; fet it upon a Table, then take a lighted Pipe of Tobacco, and put the Bowl of it in your Mouth, cloathing it with Paper, if it be too hot, and put in the little End of it at I or K, upon the Bottom of the Glafs, and blow the Smoak of it as hard as you can into the Glafs, till it comes very thick out of the Orifice EF, and filling the Glafs, renders it quite dark or untransparent, which it will do very foon; then take the Pipe out of it, ftaying till the Smoak in the Glafs has in fome measure loft the chiefeft Part of its Motion, and stands ftill like a ftagnating or gently moving Water, and represents a kind of a Superficies above at A B; then take a Nail G C, about a large handful in Length, and hold it with a Pair of Tongs a little above the Point C, or a little higher, (having first made it red hot for that Purpose) and place it in a dire& perpendicular Pofture, as at GC; then beginning, as at H, let the hot Point

of the faid perpendicular Nail gently defcend from H to C; and you will fee as foon as the fame is come from H to C, or to the Superficies of the Smoak A B, that the faid Air and Smoak will creep along the Nail, and afcend in a direct Stream from Cto L; which especially from C to D, or fo far as it remains below the Brim of the Mouth of the Glass, will preserve its Streightness; and fometimes, even as high as at L, when the Air in the Room is very still, which otherwife is wont to scatter and disperse this Column of Smoak as foon as it rises above the Brim of the Glass. To all which Circumstances, as minute as they are, you must carefully attend, if you would make the Experiment with its requifite Niceness. Now what has been faid before is made good by this Experiment.

SECT. XXXVIII. Convictions from what has been represented about the Air in general.

Now will any Body deny, that the Wisdom of our great Creator does in all these things far furpass the Thoughts of Men; who for fo many Ages has been pleased to make use of such various Methods, and perhaps of many more too, to turn the Air into Winds; tho' it is very certain, that the Knowledge of most of these kinds of Winds, yea, of all that owe their Origin to the Gravity and Elafticity of the Air, and perhaps too of fuch as are produced by Heat and Cold, has been concealed till lately from the whole World; and who can tell, but that thofe that are still hidden, may be referved for the Difcovery of our Pofterity?

A

At least, a generous Philofopher may learn from hence to entertain very humble Sentiments of his own Knowledge, and to fee the Fallacy and Sophiftry of thofe ftrong Minds, who fancy they

can

1

can fathom every thing. First, Because we have. feen fo many and fo famous Naturalifts in thofe Times, treating with fo much Certainty, and even with the Approbation of very Learned Men, about the Winds; who, if the Experiments of following Years, touching the Motions of the Air, had been known to them, would have even been afhamed of the Conceit of their own Skill therein. Secondly, Because, as has been juft now hinted, even in these our Times, in which the Grounds of the Knowledge of the Winds have been fo much augmented by new Experiments, the greatest Mathematicians and Enquirers into Nature, that speakfincerely, have openly confefs'd how far they ftill are from attaining to a true Notion of these things.

But if an unhappy Atheist cannot be yet brought by these Representations of the Greatness of Go D, and of his own Meanness, to confefs the Power of his Adorable Creator; let him (if this may in any wife contribute to fet him right) I fay, let him with us contemplate the Globe of the Earth Z F G (Tab. XIV. Fig. 3.) and obferve, that there are found upon the fame fo many humane Creatures at F, fo many Beasts at M, fo many Fishes at V, fo many Birds at X, fo many Trees and other Plants at O, fo many stately, Palaces and other Buildings in Cities and Towns, at P, fo many Fires for the Ufe and Service of Mankind at Z, fo many Ships at N, which may pafs from one end of the World M, quite to the other G: And to fay no more, let him, feriously confider all the Wifdom and Art wherewith each of these things have been made after fo wonderful a manner: Further, let him fup+ pose all those Men and Beafts to be without any Life or Motion; the Fishes divefted of the Power of Swimming, the Birds of Flying, the Fire of Burning, the Trees and Plants of Growing; let him fancy all the Towns to be uninhabited, and

all

all Communication between the most remote Countries interrupted for want of Shipping; Will not the whole Globe of the Earth, with every thing that is upon it, appear to him a most Melancholy and moft Frightful Wilderness? But now if any one fhould come and tell him, and cont vince him too by ocular Demonftration, that it was poffible to endow a certain fluid and invifible Matter furrounding this Globe with fuch wonderful Qualities, that by means of the fame, fo many Millions of Men, and other Creatures would live; that the Fishes which he now fees floating upon the Water, would fubfift under them; that the Birds hou'd be able to fly, the Trees and Plants to grow for the Suftenance of fuch Creatures; that Fire would burn for the Preparation of Food, for Light, and a thousand other Ufes; that Ships, tho' loaded with a most surprising Weight and Burden, would be carried to the remoteft Parts of the World, by the ftrength of the faid invisible Matter; not to recount all the other Services that are render'd thereby to those who inhabit this Globe: would he not, after having seriously weighed all these things, confefs the Discoverer or Inventer of fuch a Fluid, to be wonderful Wife? Or, could he imagine that this Matter, deftined to fo many different and important Purposes, was capable of acquiring by Chance, and without Wisdom, the Properties neceffary to produce not only fo many and fuch great Things, but of ranging and diffufing itself, of its own accord, quite round the World? And can he then continue to affirm the fame of the Air, by which he lives, and from which he reaps fo many advantages, which does all this, and much more ftill? Efpecially if his Knowledge extends fo far as to be able to compare the Structure of Men, Beafts, Birds, Fifh, Plants and other things; (of which fomething has

been