an elaftic force equivalent to the preffure; but one would think it could require no great conjuration to discover, that the mercury, in the circumftances above mentioned, is kept up merely by the water occupying the whole capacity of the veffel, fo that there is no vacuity for the mercury to fall into: none of it could fall without difplacing an equal bulk of the water, and the water is fo confined that it cannot be difplaced. Though the mercury were forced up 29 feet as well as 29 inches, if the tube be connected at bottom with a clofe veffel quite full of water, it will be as effectually kept up, though the water has received no previous preffure, as it would be at the bottom of the ocean.

The Author obferves in his Preface, that at the exhibitions of air-balloons, the bulk of mankind have appeared to be wonderfully ignorant ;-people flocking by thousands to fee the phenomenon of an air-balloon afcending and fwimming in the atmofphere, a fight or fpectacle which, to the populace, muft appear wonderful ;-but if the principles of hydrostatics had been known, the afcending and fwimming of an air-balloon could not be confidered as a wonderful phenomenon.'

That a body really lighter than air fhould afcend and float in the air, is certainly not wonderful; but that a balloon, with its ponderous appurtenances, and one or more men in it, should, all together, be really lighter than common air, has appeared wonderful to those who were better fkilled in, hydroftatics, and pneumatics too, than this writer; nor does he, after all, even pretend to explain or understand the mystery. He tells us, that the balloons are filled with ignited or igneous matter;—that he does not apprehend they have any thing to do with adual flame, because flame would confume them, and because there can be no flame without a free accefs of air;-but that if a laceration or crevice should happen in the coat or cafe, flame might be the confequence, unless the igneous matter was composed of ingredients to prevent flame ;-that there is a great variety of igneous bodies with which balloons may be filled, as fpirit of wine, fpirit of vitriol, phosphorus, and many more, by which the air within the balloon may be ignited and rendered inflammable ;-with other circumftances of the fame kind, which, to a philofopher unacquainted with the matter of fact, would render it not only wonderful, but incredible.

This writer, whofe name we find to be Geo. Urquhart, appears to us to be more converfant in law than in philofophy; his ftyle being very remarkably embellifhed or embarraffed with the repetitions and reduplications appertaining and belonging to the fcience or profeffion firft above named. The effay on air-balloons is a curiofity in this way, and we fhall endeavour to entertain our readers with a fketch of it. It is introduced in the following terms:

If air-balloons could be rendered fafe vehicles for carrying or conveying mankind through the air, from one place or country to another wifhed-for place or country, or from one kingdom, ftate, or nation, to another wifhed-for kingdom, ftate, or nation, it would verify, in fome fenfe, the faying of the immortal Horace, Calum ipfum petimus, not ftultitia, as he added, but fapientia, as might juftly be added by modern mortals; and whether air-balloons are or are not, in the nature of things, likely to become or to be rendered useful to mankind, as fafe vehicles of conveyance from place to place, or more likely to be and remain ufelefs to mankind, as they have been, fo far as is known, from the beginning of time to this day, is the matter to be inquired into by this effay.'

Proceeding regularly in this enquiry, he firft establishes the fact, or the reality of air-balloons: That air-balloons (he fays) have lately been formed and conftructed, in France, in England, and in other countries, and have been made to afcend in the atmosphere to confiderable heights, to fwim there during feveral hours, and to move along and through the air to diftances equal to many miles, measured on the earth, is not now to be controverted, and cannot be denied, after various accounts and relations have been given, and published at different times, by men of veracity, in different countries, of various trials and excurfions made by them with air-balloons, and of the refults and effects of thofe trials and excursions, related by the adventurers who made the experiment.'

He particularifes fome of thefe excurfions, and left it should be fufpected that a balloon can carry only one man, he adds, that in philofophy, no doubt can be entertained, but what a balloon, capable of taking up one man, may, by increafing its power of afcending and swimming, be made capable of taking up two men, or three men, or even more. As to two men, no doubt can remain, because Mr. Blanchard's balloon carried Mr. Sheldon and him, without any difafter that has been heard of, as far as Sunbury. thofe circumftances and confiderations, therefore, there is fufficient ground for crediting accounts from France, wherein were mentioned inftances of balloons there that afcended and fwam with two, three, and even more perfons.'

From

This important point being fettled, Mr. U. mentions fome cafes in which the expectations of the Public were difappointed, and enumerates fome philofophical obfervations which the airballooners might have made if they had been fo difpofed. And, fince nothing has been faid of thofe matters which might be of utility to science, it is natural to think that nothing more was intended by thofe balloon exhibitions than giving a fight or fpectacle of admiration to the rich and poor, the learned and unlearned, the great and the little populace, for a fmall tribute, contributed and paid by them, in confideration of fo fublime a spectacle.'

This, to be fure, is a ftrong prefumption against the utility of air-balloons, but a much stronger arifes from the nature of the igneous matter they are filled with. What this matter is, our Author does not pretend to know; for thofe' (he fays) who

16

have

have been employed or concerned in filling the balloons of Mr. Lunardi, Mr. Blanchard, or other air-ballooners, feem to have made their igneous matter an arcanum, or fecret, to be kept to themselves, for to the Public they have difcovered or faid nothing about it.'

But he gives us a long detail (near a dozen pages) on the action of fire, and phlogifton, and igneous matter in general, from which the following conclufion is drawn: All these being circumstances and facts in natural philofophy, relative to the elements of fire and air, and the effects of those elements upon or against one another, in various cafes and conjunctures; in or concerning which (and many more fuch there are) no philosopher has hitherto been able to discover, fix, or fettle, any certain rule or rules for mankind's knowing, judging, and investigating all the true caufes of natural phenomena, or all the true effects produced by their true caufes, in the cafes of fire and air acting upon one another, or the power that any given quantity of fire, or of igneous matter, can exert in operating upon or affecting the atmosphere, or any part of it; or the power that the atmosphere, or any part of it, can exert, either in oppofition to or in concurrence with fire, or igneous matter; nor has nor have any certain or known datum or data been ever given concerning the fame, for the ufe or benefit of mankind. The confequence, in conclufion, therefore, is, that air-balloons, depending upon fo great a variety of intricate, precarious, inconftant, unequal, defultory, unknown, and unforeseen circumftances and viciffitudes, can never be rendered useful to mankind, as fafe vehicles of conveyance from place to place.'

To all this fine reasoning it may be objected, that marine navigation was probably as unpromifing in its infancy as aerial navigation is now. The Author ftates this objection with his ufual verbofity, together with his answer, of which we can tranfcribe only a part. In regard' (he fays) to veffels of wood floating and moving, or fwimming, on the furface of the water, it was impoffible for mankind to live long, or for a confiderable time, in fociety, without obferving that wood, or a piece of wood, would fwim ou the furface of the waters, and could not be drowned or funk, without fome weight being laid upon or faftened to fuch wood, or pieces of wood;-and thus, by degrees, veffels of wood, great and small, came to be conftructed and built, of fuch figure and fize, as were fitted and adapted for floating and fwimming on the feas and waters, with great weights and loads, and many perfons carried in them, and conveyed from place to place.-But what analogy can there be found, or fet up, or what comparifon, from the cafe of navigation, or of fhips or veffels fwimming on the feas or waters, to the cafe of airballoons afcending on high, and fwimming in the atmosphere? which being neither vifible, nor tangible, nor perceivable by the fenfes ; and a medium, element, or fluid, in which no folid wood, or piece of folia wood, ever floated, or ever will float in the air.’

And, upon the whole, fince Mr. Boyle, Sir Ifaac Newton, or any other of the great philofophers of England, France, Holland, Germany, or Italy, has not profeffedly mentioned any thing concerning air balloons, nor recommended them to mankind as poffible to be rendered

rendered useful vehicles of conveyance, there is great reason to apprehend, that no Montgolfierian philofopher of the prefent age can ever render them useful vehicles of conveyance to mankind.'

The Appendix contains a particular account of fome aerial excurfions, with remarks on each; the fubftance of which remarks is, where any accident on untoward circumftance happened, that fuch eternally must be the cafe; and where accidents did not happen,-why then, they might have happened, and therefore no human art can make balloons to become useful or fafe vehicles of conveyance to mankind from place to place.

Having now laid before our Readers the whole fubftance of this extraordinary effay, we fhall, for once, join issue with the Author, and leave his performance to float [if it can] by the potentia of its merit, or to fink by the pondus of its demerit.' Potentia and pondus are two terms which he has introduced into hydroftatics, analogous to power and weight in mechanics.

ART. VI. Sermons, by G. Gregory, F. A. S. Author of Effays Historical and Moral, &c. To which are prefixed, Thoughts on the Compofition and Delivery of a Sermon. 8vo. 6s. Boards. Johnson. 1787.

IN

N an age fo much distinguished as the prefent, by a spirit of improvement, it is reasonable to expect, that while other arts are making a rapid progrefs, the art of preaching, conftantly exercifed by fo many,-for "great is the companyof the preachers"-fhould not remain in the defective ftate in which our ancestors left it. If this art were studied and practised with the degree of attention which it deferves, there can be no doubt, that it might be made much more useful to fociety, than it has hitherto been. Several laudable efforts for this purpose have been made by preachers of different orders; particularly, by fubftituting the interefting topics of practical morality in the room of fyftematical fpeculations, and a pointed application to prefent manners, inftead of trite and common-place declamation. Preaching, as it is at prefent managed by the more judicious of the clergy, is a manly addrefs to the understanding, and to the heart, in favour of virtue, wherein, acknowledged truths (in Lord Bacon's phrafe) are " brought home to men's bufinefs and bofoms." Several very excellent fpecimens of this kind of preaching have, in our own time, been offered to the Public, and we are happy in being able to add to the refpectable catalogue, the volume now before us.

Thefe difcourfes, though for the most part on common topics, poffefs a degree of originality, both in thought and manner, fufficient to render them interefting. They abound with good fenfe, and useful reflections, judiciously applied to the purpose of

feasonable

seasonable inftruction. They are written with that ftrength of language, which is the natural effect of ftrong conception, and are a pleafing fpecimen of that kind of manly eloquence, which compaffes its end without any wafte of words. The reader may fometimes regret that the Author has not faid more on a subject -for the fermons are very fhort-but will feldom think that he has faid too much.

The following extract from a difcourfe, in which the characters of the Hypocrite and the Libertine are compared, will give our Readers a juft idea of Mr. Gregory's talents for animated addrefs.

After pointing out the refemblance between modern hypocrites and the Pharaifaic fect among the Jews, he thus proceeds:

Approach now, you, who pride yourfelves, if I may fo speak, in the fincerity of your fin! You, who defpife diffimulation equally with-virtue. Now exult.-Now is your hour. You have feen religion made the cloak of vice; you have feen pretended fanctity fhield from punishment-in this world. Proceed; tell us," that piety is all an illufion;-that it is an inftrument in the hands of the crafty."—" Happy for us," (you will add,) "this is not an age favourable to hypocrify."-Indeed it is not; and yet perhaps we are no gainers by the boafted revolution. Here, then, end the triumph of the libertine.-For, tell me, you who reafon for yourfelves, and are not carried along the ftream of popular prejudice: because there is hypocrify, is there no fuch thing as real virtue? Because there are pictures, are there no originals? The hypocrite, indeed, abufes virtue, by ufing its femblance to evil purposes; but the libertine ftrikes at its very existence. The one tacitly confeffes its excellence, while he pretends to imitate it; the other difowns its attributes, and fpurns its authority. The one may indeed injure a few individuals; the other muft injure the Public, by fupporting principles, and by affording an example, which fap the very foundations of all morality and good government.

But, are thefe characters fo totally distinct, that the libertine is on every occafion free from hypocrify? When fome vile end is to be accomplished; when fome criminal paffion is to be gratified; does he then fcruple to diffemble? No:-he affects to defpife it, because his general conduct is too flagrant to admit of hypocrify. He, who wears in common that difguife, must be a petty finner, or he is prefently detected. But, when every art is exhausted to fupport a tottering reputation, the laft refource of proflicacy is to intrench itfelf in an infolent effrontery, which fets at defiance God and man. Let us not mistake; there is a nearer affinity between thefe two denominations of finners than either of them is willing to acknowledge. The hypocrite is no other than a painted libertine; and, when the varnifh is washed away, he ftands revealed juft the fame falfe reafoner, the fame contemptible flave of appetite and paffion, as the audacious profligate, who affects to difdain the concealment of his vices. That there is little temptation to hypocrify, and little occafion for it at prefent, will not, I fear, prove to the honour of the prefent age; and yet there are not wanting perfons unimpeachable in their own

conduct;