KER, and BURNS, of Great-Britain. To attempt am enumeration in detail of all the inventions, discoveries, and useful suggestions produced by these several philosophers and artists, would swell this account beyond all bounds. It is sufficient to say, that although that part of the science of hydraulics which relates to mills, did not arrive at absolute certainty and perfection in their hands; yet they made so many successive additions to the knowledge of preceding theorists, that to each large acknowledgments are due from the friends of human improvement. Nor ought the still later inquiries of our countrymen, Mr. WARING, on the same subject, to be forgotten. His memoir on the maximum velocity of a wheel or other body, moved by a given quantity of fluid, may be regarded as a singular monument of accurate and successful investigation, The theory of mills; which he deduces from his experiments and calcu lations, is said to correspond with fact, to a degree greatly beyond all other attempts."

The various improvements which the last century produced in the construction of pumps, are also worthy of notice. Since the doctrine of the pressure of the atmosphere has been reduced to a regular system, and the general laws of moving fluids have been better understood, several advantages in the formation and management of this class of engines naturally followed. Those who most distinguished themselves during the century, by inventions, or laborious investigations, on this subject, are Messrs. HADLEY, DESAGULIERS, HASKINS, and BEIGHTON, of Great-Britain, Messrs. J. and D. BERNOULLI, and WIRTZ, of Switzerland,

g See Trans. Amer. Philos. Society, vol. iii.

Mr. WARING was an obscure character, a native and resident of Philadelphia. He belonged to the Society of Friends, and taught a school in that city. Though little known, he was a real philosopher. He died of the pestilence which raged in that city in 1793..

and Messrs. PITOT, BOSSUT, BELIDOR, DE LA BORDA, D'ALEMBERT, DE LA GRANGE, and DE BUAT, of France.

PNEUMATICS.

In Pneumatics, or that science which treats of the mechanical properties of elastic fluids, modern discoveries and improvements have been very nu merous and important. Ever since the famous Torricellian experiment, in the seventeenth cen tury, proved that air was a gravitating substance, the attention of philosophers has been employed, with great success, in investigating the properties, and ascertaining the laws of this fluid. By nume rous and patient inquiries, they have gone far toward reducing to regular system the principles which govern the density, the weight, the elasticity, and the motions of the atmosphere. And the various mechanical properties of air, as they became, in succession, better understood, have been rendered subservient to the utility of man, by their application to the arts of life.

The Barometer has, within the last century, received many and most important improvements, from ROWNING, DE LUC, ROY, SHUCKBOURGH, CASWELL, NAIRNE, JONES, and others. The application of this instrument to the measurement of altitudes was first suggested by Dr. HALLEY, and afterwards better explained and systematized, by several of the gentlemen just mentioned, especially by the celebrated M. DE LUC, of Geneva. The Air-Pump, during the same period, was much improved by HAWKSBEE, GRAVESANDE, Abbé NOLLET, SMEATON, RUSSELL, our ingenious coup

See Encyclopædia, Art. BAROMETER and PNEUMATICS. See also Philosophical Transactions, vol. lxxvii.

tryman, the Rev. Dr. PRINCE, of Salem, LAVOI¬ SIER, and finally by CUTHBERTSON, of Amsterdam; by the last of whom, we are taught to believe, this machine has been carried to a degree of perfection beyond which little advancement is to be expected. That part of pneumatics, also, which relates to the construction of Chimnies, the comfort of human habitations, and the economy of fuel, has been, in modern times, the subject of much inquiry, and most useful improvement, by Dr. DESAGULIERS and Mr. ANDERSON, of Great-Britain, and by the illus trious Americans FRANKLIN, COUNT RUMFORD, and many others. To which may be added a number, almost countless, of wind instruments and machines, which modern ingenuity has invented, and which have grown out of our increasing knowledge of the qualities and laws of the important fluid in which we are immersed.

In this period, beyond all doubt, we are to place the invention of BALLOONS. In 1766, the Hon. HENRY CAVENDISH discovered that inflammable air (the hydrogen gas of the French nomenclaturists) was at least seven times lighter than common air. It soon afterwards occurred to the celebrated Dr, BLACK, that if a thin bag were filled with this gaseous substance, it would, according to the established laws of specific gravity, rise in the common atmosphere; but he did not pursue the inquiry. The same idea was next conceived by Mr. CAVALLO, to whom is generally ascribed the honour of commencing the experiments on this subject. He had proceeded, however, but little way in these experiments, when the discovery of STEPHEN and JOHN MONTGOLFIER, paper manufacturers of France, was announced in 1782, and arrested the attention of the philosophical world.

See the Transactions of the Amer. Acad. of Arts and Sciences, vol. i.

Observing the natural ascent of smoke and clouds in the atmosphere, those artists were led to sup pose that heated air, if enclosed in a suitable covering, would also prove bouyant. Accordingly, after several smaller experiments, by which this idea was fully confirmed, they inflated a large bal loon with rarefied air, on the 5th of June, 1783, which immediately and rapidly rose to the height of six thousand feet, and answered their most sanguine expectations. It was soon found that machines of this kind might be so contrived as to convey small animals, and even human beings, through the air with ease. The first human adventurer in this ærial navigation was M. PILATRE DE. ROZIER, a daring Frenchman, who rose in a large balloon, from a garden in the city of Paris, on the 15th of October, 1783, and remained a considerable time suspended in the air. He made several ærial voyages of greater extent afterwards, and in two of them was attended by other persons. In a short time, however, the use of rarefied air in aerostation was, for the most part, laid aside, as inconvenient and unsafe, and recurring once more to the discovery of Mr. CAVENDISH, the philoso phers of Paris concluded that a balloon, inflated with inflammable air, would answer all the purposes of that contrived by the MONTGOLFIERS, and would also possess several additional advantages. They made their first experiment on the 23d of August, 1783, which was attended with complete success; and the first human beings who ventured to ascend in a balloon raised upon this plan, were Messrs. CHARLES and ROBERTS, who rose from Paris, on the 1st day of December in the same year. The inflammable air balloons have been generally used since that time; many ærial voyages have been performed in Europe and America; and what is remarkable, out of all the numer

ous instances of such hazardous enterprize, only one is recollected, which was attended with any fatal accident."

The invention of balloons, though far-famed and brilliant, cannot be considered as having hitherto added much to the comfort or utility of man. The only practical purposes which it has been made to subserve, are those of aiding in meteorological inquiries, and inspecting the fortifications, and reconnoitering the camp of an enemy, which could not be approached by other means. It has been applied to this latter purpose in at least one, if not more instances, by the French engineers, during the late war." But who can undertake to assign the limits beyond which the ingenuity and the enterprize of man shall not pass? Though this species of navigation labours under difficulties which appear at present insurmountable; though the want of some means to controul and regulate the movements of the ærial vessel is so essential as to excite a fear that it cannot be supplied; yet who can tell what further experience and discoveries may produce? Who can tell but another century may give rise to such improvements, that navigating the air may be as safe, as easy, and rendered subservient to as many practical purposes, as navigating the ocean? It must be acknowledged, indeed, that this is not very probable; but things more unexpected, and more remote from our habits of thinking, have doubtless occurred.

Under this head also properly come the great improvements which have been lately made in Steam Engines, doubtless among the most im

There is a reference here to the death of M. PILATRE DE ROZIER and M. ROMAIN, who rose in a balloon, from Boulogne, in the month of June, 1785, and after having been a mile high, for about half an hour, the bal loon took fire, and the two adventurers were dashed to pieces by their fall.

m GREGORY'S Economy of Nature, vol. i, p. 515,