AERATED WATERS.

patented, and likely to come into use. In ordinary bread-making, the wheat-flour is moistened with water and worked into dough, to which common salt and yeast are added. The latter causes the flour to ferment or decompose, when carbonic acid is given off at every part; and when the fermented dough is placed in an oven, the bubbles of carbonic acid gas expand, and cause the formation of the spongy mass characteristic of well-made loaf-bread. The new process of preparing A. B. consists in placing the flour in a strong enclosed iron box, and moistening it with carbonic acid water, prepared as stated under A. WATERS. The dough is then worked up by machinery inside the box, and in ten minutes or so, it is taken out, shaped into loaves, and placed in an oven, when the carbonic acid, previously introduced with the water within the dough, expands, and forms a light palatable bread. The advantages which this method of working bread has, as set forth by the patentees, are-1. There is a saving of the whole of the waste caused by fermentation, which averages fully 10 per cent. Thus 10 per cent. more bread is made out of a sack of flour than by the old process. 2. The process, instead of occupying eight or ten hours, is completed in half an hour. 3. The cost of machinery and gas is less than that of yeast used in the old process. 4. The dough requires scarcely any handling to form it into loaves. 5. The bread is absolutely pure-it is simply flour, water, and salt. Finally, should the whole of the bread in the kingdom be thus made, a great saving would be effected in the consumption of flour. See UNFERMENTED BREAD.

upper division. The powders, consisting of bicar
bonate of soda (NaO,HO,2CO,) and tartaric acid (T),
are then placed in the upper globe by means of the
small funnel D, and care is taken, by plugging up
the tube communicating with the lower part by the
stopper F, that no powder passes into the larger
globe. The long tube, C, is then inserted into the
globes, and screwed well in.
The apparatus is
inclined till water from the lower globe enters and
fills the upper globe about one-third; then it is
placed erect, and allowed to be at rest for two hours,
when, if the screw stop-cock at the upper part be
opened, the carbonated water will flow out readily
into any vessel placed to receive it. The explana-
tion of the action which goes on in the vessel is,
that tartaric acid and bicarbonate of soda have
no action on each other so long as they are dry;
but whenever water is admitted, the tartaric acid
combines with the soda and water to form tartrate
of soda and water (NaO,HO,T), and at the same
time, carbonic acid (CO) is given off, and descend-
ing the tube into the lower globe, dissolves in the
water contained therein. Occasionally, bisulphate
of potash is used instead of the tartaric acid, to save
the greater expense of the latter.-The gazogènes can
likewise be used in the preparation of true soda-
water, or Eau de Vichy, by adding a little car-
bonate of soda to the water in the lower globe before
charging with carbonic acid. A. wine may be
obtained by placing white wine with a little sugar-
candy in the lower globe instead of water. Spark-
ling lemonade is procured when the carbonic acid
water is run into a tumbler containing a little
sirup of sugar; and A. fruit-beverages, when the
water charged with carbonic acid is received in a
glass containing about a table-spoonful of either of
the fruit-sirups.

AËRATED WATERS are employed largely as refreshing, refrigerant beverages to allay thirst during warm weather, and during feverish conditions of the animal frame. The most common A. beverage is Carbonic acid water, generally spoken of as Soda- The less common A. W., prepared on the large water, though it seldom contains any soda. It is pre-scale, are-1. A. soda-water (true soda-water), obtained pared on the large scale by placing whiting, chalk, by adding 15 grains of crystallised carbonate of or carbonate of lime (CaO,CO2) in a lead vessel soda to each bottle before it is charged with the carbonic acid water; 2. A. potash-water, by employ ing in a similar way 20 grains of bicarbonate of potash; 3. A. Selters-water, when carbonate of soda and chloride of sodium (common salt) are dissolved in carbonic acid water; 4. A. Carrara-water, when finely divided Carrara marble is dissolved in the acid-charged water; 5. A. lime-water, when other forms of lime than the Carrara marble are used; 6. A. magnesian-water, when magnesia, or the carbonate of magnesia, is used; and A. chalybeate-water, when a compound of iron is dissolved in the carbon c acid water. The latter beverage has lately been employed in medicine, as an easy means of introducing iron into the blood, and with good effect. A. Carrara and lime waters are now administered in cases where the bony structure requires to be strengthened; and A. magnesia-water is a very agreeable mode of giving a patient a dose of magnesia. The well-known effervescing draughts called soda-powders, and seidlitz-powders, are two other kinds of A. drinks. In the former, bicarbonate of soda and tartaric acid are added to water in a tumbler, and a refreshing draught instantaneously prepared. Seidlitz-powders contain tartrate of soda and bicarbonate of soda in one paper, and tartaric acid in the other; and when both are added to water, effervescence ensues, and the liquid is then partaken of.

Gazogène.

with water and sulphuric acid (SO), when the sulphuric acid combines with the lime to form stucco or sulphate of lime (CaO,SO,), and carbonic acid (CO2) is evolved as gas. The latter is received in a reservoir, and is thereafter forced into water, so that the latter dissolves about five times its own volume of the gas. The water then constitutes a brisk sparkling liquid, with a pungent, but pleasant acidulous taste. On the small scale, and for family use, carbonic acid water may be conveniently prepared in the apparatus known as the gázogene or seltzogène. The complete apparatus is seen at A. and dissected at B. and C. In proceed ing to use the vessel, the lower globe at B. is filled with water by means of the long funnel E, taking care that no water runs into the smaller and

A. W. likewise occur naturally. Water, as it is drawn from a spring, tastes differently from the same water after being boiled and cooled; and this is due to the unboiled water containing the gases oxygen, nitrogen, and carbonic acid-especially the latter-dissolved in it. Spring-water is therefore natural A. beverage. Rain-water has a mawkish,

AERIAL POISONS-AEROLITES.

insipid taste, mainly because of the minute quantity phers as instances of popular credulity and superof gas therein dissolved; but when that rain-water stition. It was not till the beginning of the 19th c. trickles down the mountain-side, and is dashed that the fact was established beyond a doubt.from ledge to ledge of rock, it absorbs and dis- According to Livy, a shower of stones fell on the solves the gases from the air, and is thus naturally Alban Mount, not far from Rome, about 654 B.C. aërated. Many waters are aërated in a natural but The fall of a great stone at Ægospotami, on the peculiar way, which confers upon them important Hellespont, about 467 B.C., is recorded in the Parian medicinal properties; and these will come before us Chronicle (q. v.), and mentioned by Plutarch and under their more popular title of Mineral Springs. Pliny. It was still shewn in the days of Pliny AË'RIAL POISONS. See MIASMA. (d. 79 A.D.), who describes it as of the size of a wagon, and of a burned colour. In the year 1492 the sky near the village of Ensisheim, in Alsace; A.D., a ponderous stone, weighing 260 lbs., fell from part of it is still to be seen in the village church. An extraordinary shower of stones fell near L'Aigle, in Normandy, on the 26th April 1803. The celebrated French philosopher, M. Biot, was deputed by government to repair to the spot and collect the authentic facts; and since the date of his report, the reality of such occurrences has no longer been questioned. Nearly all the inhabitants of a large district had seen the cloud, heard the noises, and observed the stones fall. Within an elliptical area of seven miles by three, the number of stones that had fallen could not be less than two or three thousand; the largest were 17 lbs. in weight. These are only a few out of hundreds of instances on record.

AERODYNAMICS is that branch of science which treats of air and other gases in motion. It examines first the phenomena of air issuing from a vessel, which correspond in many respects with those of water. See HYDRODYNAMICS. Much depends, as in the case of water, upon the nature of the orifice, whether a mere hole in the side of the vessel, or a tube or adjutage. Another subject of A. is the motion of air in long tubes, where the resistance of friction, &c., has to be ascertained. That resistance is found to be nearly in proportion to the square of the velocity, to the length of the tube, and inversely to its width. A. examines also the velocity of air rushing into a vacuum, of wind, &c. The instrument used for the latter purpose is called an anemometer. See WINDS. Air is found to rush into a void space at the rate of from 1300 to 1400 feet per second. One of the most important inquiries in A. is the resistance offered to a body moving in air, or-which is the same thing-the pressure exerted by air in motion upon a body at rest. The law may be stated, with sufficient accuracy for practical purposes, as follows: The resistance or pressure is proportional to the square of the velocity. We might conclude from reason, without experiment, that such would be the case; for if one body is moving through the air four times faster than another of the same size, not only will it encounter four times as many particles of air, but it will give each of them four times as great an impulse or shock, and thus encounter 4× 4, or sixteen times as much resistance.

This resistance is greatly increased by another circumstance, especially with great velocities. The air in front of the moving body becomes accumulated or condensed, and a partial or even entire vacuum is formed behind it. With a velocity of 1700 feet per second, for instance, the resistance is found to be about three times as great as the simple law of the square of the velocity would give. By the operation of these laws of resistance, a heavy body let fall with a parachute attached to it, comes, after a certain time, to move with a velocity approaching more and more nearly to a uniform motion.

A'EROLITES (Gr. aer, air, and lithos, stone), or METEORIC STONES, FIREBALLS, and SHOOTING-STARS, are now classed together as being merely varieties of the same phenomenon. Aërolites that fall during the day, are observed to be projected from a small dark cloud, accompanied by a noise like thunder, or the firing of cannon; at night, they proceed from a fireball, which splits into fragments with a similar sound. It is believed that the dark cloud that accompanies the fall of aërolites by day, would be luminous at night; and smoking, exploding fireballs have sometimes been seen luminous even in the brightness of tropical daylight. The connection between aërolites and fireballs is thus established. Fireballs, again, cannot be separated from shootingstars, the two phenomena being sometimes blended, and also being found to merge into one another, both with respect to the size of their disks, the emanation of sparks, and the velocities of their motion.

There are numerous records and stories in all ages and countries of the fall of stones from the sky; but until recent times, they were treated by philoso

As was natural with objects of such mysterious origin, meteoric stones have always been regarded with religious veneration. At Emesa, in Syria, the sun was worshipped under the form of a black stone, reported to have fallen from heaven. The holy Kaaba of Mecca, and the great stone of the pyramid of Cholula, in Mexico, have all the same history.

The existence of such bodies once admitted, led

to assigning a meteoric character to strange ferruginous masses found in different countries, and which had no history, or were only adverted to in vague tradition. Of this kind is the immense mass seen by Pallas in Siberia, now in the Imperial Museum at St. Petersburg. The largest known is one in Brazil, estimated at 14,000 lbs.

One constant characteristic of meteoric stones is the fused black crust, like varnish, with which the surface is coated. From the circumstance of this coat being very thin, and separated from the inner indicate some rapid action of heat, which has not had mass by a sharply defined line, it is thought to time to penetrate into the substance of the stone. This view is favoured by the fact that the stones are found in a strongly heated, but not incandescent state, when they fall. Their specific gravity ranges from two to seven or even eight times that of water.As to their chemical composition, the predominating element is iron, in a native or metallic state, generally combined with a small proportion of nickel. According to Humboldt, the aerolites that fell in the neighbourhood of Agram, in Croatia, in 1751, the Siberian stone, and specimens brought by that philosopher from Mexico, contain 96 per cent. of iron; while in those of Sienna the iron scarcely amounts to 2 per cent., and, in some rare instances, metallic iron is altogether wanting. A writer in the Quarterly Review, No. CLXXXIII., thus sums up the result of all the chemical analyses hitherto made: 'We find the actual number of recognised elements discovered in aërolites to be nineteen or twentythat is, about one-third of the whole number of elementary substances (or what we are yet forced to regard as such) discovered on the earth. Further, all these aerolite elements actually exist in the earth, though never similarly combined there. No new substance has hitherto come to us from without; and the most abundant of our terrestrial metals, iron, is that which is largely predominant in aërolites, forming frequently, as in some of the instances juɛt

AEROLITES.

blende, and other earthy minerals; and closely resembling certain crystalline compounds which we find on the surface of the earth.'

mentioned, upwards of 90 parts in 100 of the mass. | aerolites. A few there are, especially examined by Seven other metals-copper, tin, nickel, cobalt, Berzelius and Rose, containing olivine, augite, hornchrome, manganese, and molybdena-enter variously into the composition of these stones. Cobalt and nickel are the most invariably present; but the proportion of all is trifling compared with that of iron. Further, there have been found in different aerolites, six alkalies and earths-namely, soda, potash, magnesia, lime, silica, and alumina; and, in addition to these, carbon, sulphur, phosphorus, and hydrogen. Finally, oxygen must also be named as a constituent of many aerolites, entering into the composition of several of the substances just mentioned. As respects the manner of conjunction of these elements, it is exceedingly various in different

Besides those solid masses of considerable size, numerous instances are on record of showers of dust over large tracts of land; and it is remarkable that such dust has generally been found to contain small hard angular grains resembling augite. Stories of the fall of gelatinous masses from the sky are ranked by Humboldt among the mythical fables of meteorology. It has been supposed that such fables may have originated in the very rapid growth of gelatinous algae, as Nostoc (q. v.).

Fireballs and Shooting-stars.-From the height and apparent diameter, the actual diameter of the largest fireballs is estimated by Humboldt to vary from 500 to 2800 feet; others allow a diameter of about a mile. Shooting-stars are thought to have diameters varying from 80 to 120 feet. In most cases of luminous meteors, a train of light many miles in length is left behind. One or two instances are on record where the train of the fireball continued shining for an hour after the body disappeared. The heights of shooting-stars are found to range from 15 to 150 miles, at the points at which they begin and cease to be visible. Their velocities vary from 18 to 36 miles in a second. When it is remembered that the velocity of Mercury in its orbit is 26.4 miles in a second, of Venus 19-2, and of the Earth 16-4, we have in this fact a strong confirmation of the planetary nature of meteorites.

One of the most remarkable facts connected with shooting-stars is, that certain appearances of them are periodic. On most occasions they are sporadic that is, they appear singly, and traverse the sky in all directions. At other times, they appear in swarms of thousands, moving parallel; and these

swarms are periodic, or recur on the same days of the year. Attention was first directed to this fact on occasion of the prodigious swarm which appeared in North America between the 12th and 13th of November 1833, described by Professor Olmsted of New Haven. The stars fell on this occasion like flakes of snow, to the number, as was estimated, of 240,000 in the space of nine hours, and varying in size from a moving point or phosphorescent line to globes of the moon's diameter. The most important observation made was, that they all appeared to proceed from the same quarter of the heavens-the vicinity, namely, of the star 7, in the constellation Leo; and although that star had changed greatly its height and azimuth during the time that the phenomenon lasted, they continued to issue from the same point. It was afterwards computed by Encke, that this point was the very direction in which the earth was moving in her orbit at the time. Attention being directed to recorded appearances of the same kind, it was observed with surprise that several of the most remarkable had occurred on the same day of November, especially that seen by Humboldt at Cumana in 1799, and by other observers over a

AERONAUTICS-AEROSTATIC PRESS.

great extent of the earth. The November stream | suppose the asteroids composing it to be irregulariy was again observed in the United States in 1834, grouped, we see a reason why the same stream between the 13th and 14th, though less intense. should not be always of equal intensity. There may Though often vague, and in some years altogether even be periodicity in this respect too. Between absent, this phenomenon has recurred with such 1799 and 1833-the two most brilliant manifestations regularity, both in America and Europe, as to es- of the November stream on record-there elapsed tablish its periodic character. 34 years; and a brilliant display, though inferior to that of 1833, was observed in China, California and the Eastern United States, but not in Europe, Nov. 14, 1867, and another Nov. 14, 1868.

It remains to notice briefly the various opinions that have been advanced as to the origin of aërolites, and the theory of meteors in general. The hypotheses that have been formed in answer to the question-Whence come those solid masses that fall upon the earth?-are of two kinds; some ascribing to them telluric origin, and others making them alien to the earth. Of the first kind, is the conjecture This branch of science treats that they may be stones ejected from terrestrial volcanoes, revolving for a time along with the earth, of the equilibrium and pressure of air and other gases, and at last returning to it. Another theory, which and of the methods of measuring it by the barometer at one time found considerable favour, supposed that and other instruments. The expansive force or presthe matter of which aerolites are composed existed sure of atmospheric air varies with time and place. in the atmosphere in the form of vapour, and was by In a medium condition of the atmosphere, and some unknown cause suddenly aggregated and pre-near the sea-level, barometrical observations give cipitated to the earth. These conjectures are untenable in the face of the facts of the phenomena stated above, and are now completely given up.

ESCHINES-ESOP.

and such like. A vessel is divided by a horizontal partition pierced with small holes. Upon this the substance containing the colour is laid, and a cover, also perforated, is placed upon it. The extracting liquid is then poured on the top, and the air being drawn from the under part of the vessel by a pump. the liquid is forced through the substance by the pressure of the atmosphere.

the non-classical reader may get a very tolerable notion of the grandeur and fire of this greatest of all ancient dramatists.

ÆSCULA'PIUS appears in Homer as an excellent physician, of human origin; in the later legends, he becomes the god of the healing art. The accounts given of his genealogy are various. According to one story, he was the son of Coronis and the Arcadian Ischys. Apollo, enraged by the infidelity of Coronis, caused her to be put to death by Diana, but spared the boy, who was afterwards educated by Chiron. In the healing art, Æ. soon surpassed his teacher, and succeeded so far as to restore the dead to life. This offended Pluto, who began to fear that his realm would not be sufficiently peopled; he therefore complained to Jove of the innovation, and Jove slew E. by a flash of lightning. After this he was raised to the rank of the gods by the gratitude of mankind, and was especially worshipped at Epidaurus, on the coast of Laconica, where a temple and were consecrated to him. Here oriental grove elements, especially serpent-worship, seem to have been mingled with the rites and ceremonies. From Epidaurus the worship of the healing god extended itself over the whole of Greece, and even to Rome. According to Homer, Æ. left two sons, Machaon and Podalirios, who, as physicians, attended the Greek army.

Æ'SCHINES, an Athenian orator, second only to Demosthenes, whose contemporary and rival he was. Philip of Macedon was then pursuing his designs for the subjugation of the several Greek states to his own sway; and while Demosthenes advocated the policy of opposing him before it was too late, E. was the head of the peace-party. E. was a member of more than one embassy sent by the Athenians to deal with Philip; and Demosthenes accused him of receiving bribes from the Macedonian monarch, and of betraying the cause of Athens and of her allies. There is no proof that this was the case; and perhaps E. was deceived by the wily Philip into believing that he meant no harm to the liberties of Athens, and that peace was the best policy for his countrymen. The result justified the sagacious fears of Demosthenes, and condemned the selfish, isolating policy of E. When it was proposed to reward Demosthenes with a golden crown, for his patriotic exertions in defence of his country, E. Hygieia, Panaceia, and Ægle brought an accusation of illegality against the proposer, Ctesiphon. Demosthenes replied, and are represented as his daughters. His temples Eschines being vanquished, and having thus incur- usually stood without the cities in healthy situations, red the penalty attached to an unfounded accusation, on hillsides, and near fountains. Patients that were cured of their ailments offered a cock or a goat to was obliged to retire from Athens. He finally established a school of eloquence in Rhodes, which the god, and hung up a tablet in his temple, recordenjoyed a high reputation. On one occasion, he reading the name, the disease, and the manner of cure. to his audience in Rhodes his oration against Ctesi- Many of those votive tablets are still extant. phon; and some of them expressing their astonish- statue of the god at Epidaurus, formed of gold and ment that he should have been defeated in spite of ivory by Thrasymedes, represented Æ. as seated on a throne, and holding in one hand a staff with a such a powerful display, he replied: "You would cease to be astonished if you had heard Demos- snake coiled round it, the other hand resting on the thenes.' The oration against Ctesiphon and two head of a snake; a dog, as emblem of watchfulness, others are the only authentic productions of E. that at the foot of the deity. Praxiteles and other sculpHe was born 389 B.C., and tors represented the god as an ideal of manly beauty, and closely resembling Jupiter; with hair thrown up

have come down to us. died at Samos, 314 B.C.

E'SCHYLUS, the father of Greek tragedy, was born at Eleusis, in Attica, 525 B.C. We have but scanty notices of his life. He fought in the battles of Marathon, Salamis, and Platea, witnessed the fall of Darius and Xerxes, and shared in the exulting sentiments which afterwards pervaded liberated Greece. Of the seventy or ninety tragedies ascribed to E., only seven have been preserved-Prometheus Bound, the Seven against Thebes, the Persians, Agamemnon, the Choëphori, Eumenides, and the Suppliants. These are sufficient to prove that Æ. was the creator of the Greek drama in its higher form. He introduced action in place of the perpetual chorus, and dramatic dialogue to supersede the long narrations of his predecessors Thespis and Chœrilus. Scenic effects, masks, and dresses, were other improvements introduced in the plays of A. The plots of his pieces are very simple, and display no ingenuity of construction or solution. His ral tone is elevated and earnest, and shows a preference of strong to gentle emotions. Destiny is represented in its sternest aspect; gigantic heroes, Titans, and gods, rather than men, appear on the scene, and the lofty grandiloquence of the language is in accordance with the characters. In the choruses, the language is often turgid and obscure. For some reason, not well known, E. left his native city, and went to Sicily, where he was honourably received by King Hiero. Here he died at Gela, 456 B.C., and the inhabitants of the city raised a monument to his memory. In the poetical translation by Blackie,

gene

piades descended.

From them the race of the Ascle

The

from the brow, and falling in curls on each side. The upper part of the body was naked, and the lower was covered by a mantle falling in folds from the shoulders. He had sometimes a laurel-wreath on his head, and a cock or owl at his feet; or was attended by a dwarf-figure named TelesphorusASCLEPIADES, the followers of E., who inherited and kept the secrets of the healing art; or, assuming that E. was merely a divine symbol, the Asclepiades must be regarded as a medical, priestly caste, who preserved as mysteries the doctrines of medicine. The members of the caste, or medical order, were bound by an oath-the Hippocratis jusjurandum— not to divulge the secrets of their profession. In Rome, 292 B.C., when a fatal pestilence prevailed, the Sibylline books commanded that Esculapius must be brought from Epidaurus. Accordingly, an embassy was sent to this place, and, when they had made their request, a snake crept out of the temple into their ship. Regarding this as the god Æ., they sailed to Italy, and, as they entered the Tiber, the snake sprang out upon an island, where, afterwards, a temple was erected to E., and a company of priests appointed to take charge of the service and practise the art of medicine. Hippocrates is said to have descended from the Asclepiades of Cos, who traced their descent, on the mother's side, from Hercules.

ESOP, an ancient Greek writer, whose name is attached to the most popular of the existing collections of Fables. His history is very uncertain, and some critics have even denied his existence. First among these is Luther, in his preface to the German Esop,