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of stratified flinty gravel, and resting on the chalk. In the sea cliffs, near Thorpe and Southwold, Suffolk, this sea and river formation is exposed in good and clear sections, where it consists of sand, shingle, loam, and laminated clay. Some of the strata appear to have been deposited in tranquil waters.

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III. CAVERN DEPOSITS AND OSSEOUS OR BONY
CONCRETIONS.

When rounded pebbles and gravel are cemented together into a hard stone, the mass is called a conglomerate, and sometimes, plum-pudding stone; but when such a cemented mass is composed of angular and unworn fragments of rock and other materials, it is called, from the Italian, Breccia.

In mountainous districts, many fissures are found, into which have been washed by floods. These animal remains are frequently animals seem to have fallen from time to time, or into which they found covered with alluvial matter and with fragments of rocks which have been detached by frost. The whole mass is then formed, by stalactite infiltration, into what is called a bony or Osseous breccia.

Limestone hills often abound with a series of caverns with low and narrow passages from one suite to another, which hold a tortuous course through the interior of the mountain. These caverns and passages seem to have served, at some early period, as the subterranean channels of springs and rivers. In the ter

tiary period, these channels had become and remained open for the homos and shelters of animals which perished and left their

bones there. The preservation of such bones is due to the slow but constant supply of stalactite matter brought into the caverns by water infiltrating from the roof.

Cavern breccias are found in every part of the world, but at San Ciro, in Sicily, there is one of great interest. It is about 20 feet high, 10 wide, and 180 above the sea. Within it there is an ancient sea-beach formed of pebbles of different rocks brought thither from very distant places. Broken corals and shells mingle with the pebbles. Under a mass of breccia were found an immense quantity of bones of the mammoth, &c., in a dark brown calcareous marl, and many of the bones were worn as if rounded by the action of the waves. This bed of breccia is about 20 feet thick, and under it is a bed of sand filled with sea shells of recent species.

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In the south plains of Catania these pleistocene beds are intermixed with volcanic matter, which must have been thrown up while the rock was forming at the bottom of the sea, and while the clay, sand, and yellow limestone were in the course of being deposited. All these Sicilian rocks belong probably to the same period as the Norwich crag.

II. THE PLEIOCENE. 1. The Suffolk Crag.

2. The Subapennine Beds.

I. THE SUFFOLK CRAG.

The Pleiocene rocks are confined chiefly to the eastern parts of the county of Suffolk, where these beds like those of a later class in Norfolk, are called crag. This rock is a mass of shelly sand, which is much used in agriculture. The shells imbedded in it, indicate that the bed was formed in a sea of moderate depth, in most places from 15 to 25 fathoms, but in some parts deeper, land. and at the distance of about 40 or 50 miles from any The natural group of the Suffolk Crag series is divided by Mr. Charlesworth into three subdivisions, which, in the downward order, are thus designated.

1. THE MAMMALIFEROUS CRAG; which is a sandy loam and clay formed by sea and river water, and charged with shelly detritus. It occurs about Southwold in Suffolk, and Cromer in Norfolk. It contains the teeth and bones of several extinct mammalia, or animals that suckle their young.

2. THE RED CRAG; which is so called from its deep ferrugi nous or irony colour. It consists principally of quartzose sand and comminuted shells and corals, and is about 40 feet thick.

3. THE CORALLINE CRAG; which is a series of calcareous and marly strata of loose white sands, layers of shells and corals, and concretionary bands of stone. It is of very limited extent, about 20 miles in length, and three or four in breadth, covering & district in Suffolk between the rivers Alde and Stour. At Sudbourn, near Orford, in this county, there is a large quarry in this formation furnishing a soft building stone. In some places, the softer mass is divided into thin flags of hard limestone, presenting fossil corals in the upright position which they assumed in the growth.

Where the red and the coralline orags are met together in the same district, the red always lies uppermost, and both lie on the London clay. In some sections, the coralline bed seems to have suffered denudation before the red crag had been deposited on it. yellow The red crag is distinguished by its deep ochreous or colour the coralline by its white-coloured sands.

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1. Lower freshwater limestone and marl, or the gypseous series.

2. Sandstones and sand with marine shells.

3. Limestone with marine shells, or Calcaire grossier.
4. Hard, flinty, fresh water limestone, or Calcaire siliceaux.

III. THE LOWER EOCENE.

1. Lower sands with marine shelly beds.
2. Do. with lignite and plastic clay.

The strata of these low subapennine hills consist generally of light-brown or blue marl, covered by a yellow calcareous sand and gravel, imbedding fossil shells. The marl is very aluminous, containing much calcareous matter and scales of mica. Near Parma it attains a height of about 2,000 feet, abounding in marine shells. Near Sienna, the yellow sand conglomerate rests immediately on the Apennine limestone, and at St. Vignone (pronounced Vinion) it passes into a calcareous sandstone. As this yellow sand formation is superimposed upon the marl, it represents the deltas of rivers and torrents which gained upon the bed of the sea where the blue marl had been previously deposited. Geologists now acknowledge that all the subapennine tertiaries do not belong to the same period. The beds indicate three dis-rocks of this formation are used for millstones. tinct geological eras.

1. The beds of Piedmont, e.g. at Superga, are Meiocene.

2. The beds of North Italy, Tuscany, and the Seven Hills of Rome, are Pleiocene.

3. The Tufaceous formations about Naples, Ischia, &c., are Pleistocene, and Post Pleistocene.

III. THE MEIOCENE.

1. The Faluns of Touraine.

2. Part of Bourdeaux.

3. Part of the Molasse of Switzerland.

I. THE FALUNS OF TOURAINE.

I. THE UPPER EOCENE is represented in the upper marine beds of Paris, the Fontainebleau sandstone and millstone, the Kleyn Spawen beds, the Berlin tile clay, the tertiary strata about Mayence, and the freshwater formations in Auvergne.

1. The freshwater marls and limestones of Paris seem to have been formed in marshes and shallow lakes. Some of the siliceous

2. The upper marine sands consist of marls, micaceous and quartzose sand, with beds of sandstone abounding in marine shells.

The Upper Eocene is not found in England.

II. THE MIDDLE EOCENE is represented by the Paris gypsum, the beds of Headon Hill in the Isle of Wight, the Barton beds, and the Bagshot and Bracklesham sands.

Near Paris we find, below the upper marine sands, a series of white and green marls, with beds of gypsum lying under them, which are best developed at Montmartre, where its fossils were first discovered by CUVIER. The gypsum is quarried for the manufacture of the plaster of Paris.

In England, the Middle Eocene is developed in various

instances.

In French Brittany, near Dinan and Rennes, and also in the provinces bordering on the river Loire, there is a tertiary formation called by the peasantry Faluns (faloons). It consists of shelly sand and marl, and is used for agricultural purposes. Some of the shells and corals are entire, some are rolled, and others are intain a few marine and estuary shells. comminuted fragments. In some places, as at Doué, near Saumur, these sands and marls form a soft building stone, which is composed of broken shells united by a calcareous cement, and which looks much like a mass of the coralline crag in Suffolk.

1. In Headon Hill, in the Isle of Wight, we find beds of marl, clay, sand, and a friable limestone containing freshwater shells. These beds are seen in the sea cliffs, where some of the strata con

This formation exists in scattered patches of slight thickness, and very rarely exceeding 50 feet in depth. They are frequently found to rest on a great variety of older rocks, such as gneiss and clay slate. In other districts, as between the Seine and the Loire, they repose upon the upper freshwater limestone of the Parisian tertiaries. At some points south of Tours, the shells are stained a ferruginous colour, like those of the red crag in Suffolk.

The fossil shells indicate that these Faluns were formed partly on the shore itself at the level of low water, and partly at very moderate depths, not exceeding ten fathoms below that level.

II. PART OF THE BOURDEAUX BEDS.

Immense deposits of tertiary rocks are found in the country which lies between the Pyrenees and the Gironde river. Seven hundred species of shells have been found in these beds, and they

all indicate that this division of the Meiocene strata is older than the Faluns of Touraine.

III. THE MOLASSE OF SWITZERLAND.

In Savoy we find, at the northern base of the great chain of the Alps, and throughout the lower country of Switzerland, a soft green sandstone, which is probably one of the oldest Meiocene groups hitherto discovered. It is associated with marls and conglomerates and is called "molasse," derived from "mol," soft, as the stone is easily cut in the quarry. It is of very great thickness, and might perhaps be divided into several formations. No rocks of the Meiocene period are found in England.

IV. THE EOCENE.

The Eocene group of rocks is divided by Sir Charles Lyell into three subdivisions, which he calls the Upper, the Middle, and the Lower Eocene.

2. In the cliffs of Barton, the pure white sand without fossils, on which the freshwater series of Headon Hill rested, is found to repose on a marine deposit, in which 209 species of shells have been found. This is the newest purely marine bed of the Eocene series known in England.

3. The Bagshot sands consist chiefly of siliceo is sand found about Bagshot and in the New Forest. They may be divided into three beds, the upper and lower being of light yelle w sands, and the middle of dark green sands and brown clays, al' reposing on the London clay.

4. At Bracklesham near Chichester, there is a bay, bounded by a low cliff of blue clay and green sand, full of fossil shells and teeth.

The lower Bagshot sands have supplied the boulders of sandstones which are frequently found in some of the chalk valleys, and which are called Sarsden stones, and Druid sandstone, as may be seen at Stonehenge in Wiltshire, and Kitt Kotty near Maidstone in Kent.

III. THE LOWER EOCENE consists of the London clay, the Sablés (sab-lé) of the Paris basin, the mottled and plastic clays of Hampshire and London, and the nummulites of the Alps.

In the Paris basin, just below the Calcaire grossier, are extensive deposits of sand, having in the upper portion some marine beds called "lits coquilliers," in which 200 species of shells have been found. At the very base of the tertiary system in France, are beds of sands and plastic clay abounding with fossil oysters. In the lower clays and sands layers of lignite are found.

1. The London Clay consists of a tenacious brown and bluishgray clay, with layers of concretions called Septaria, which are employed in manufacturing Roman cement. The best places to study this bed are Highgate near London, the Isle of Sheppey in Kent, and Bognor in Sussex.

2. Mottled or Plastic Clays are accumulations of sand, pebbles, and mottled clays. They are well developed in some of the railway cuttings about Reading, in Berkshire; in different parts of Hampshire; and especially about Blackheath and Woolwich. In many places it appears to be a mixture accumulated by the combined action of river and sea-water. At Poole, in Dorsetshire, this clay is used for pottery, and hence the term "plastic clay."

3. The Nummulite of the Alps and Pyrenees. This is a cal- NOTES AND REFERENCES-d. Faire entendre raison au petit careous rock, consisting often of a compact crystalline limestone, B., induce little B. to listen to reason; L. S. 96, R. 4-6.il full of nummulites or shells of the class Foraminifera, or ex- s'engagea une dispute, an altercation commenced; the verb is uni tremely diminutive forms of shelly animals. As these fossils are personal.-c. from se mettre; L. S. 68, R. 3, also part ii., p. 96. very much like pieces of coin, and as nummus is the Latin ford. remit, delivered; from remettre; L. part ii., p. 102.-e. L. coin, and nummulus, is little coin, this rock is called Nummulite. S. 43, R. 6.-f. fit coudre, had it sewed; L. S. 31, R. 3.-g. In the Alps this rock is of great thickness. In many parts of causa, talked, spoke.—h from falloir; L. part ii., p. 92.-i. on Europe, Asia, and Africa, this group forms a very large part of se remit en marche, the march was resumed; L. S. 34, R. 1, 2the Tertiary formations. It is found in Algeria and Morocco; in. the verb is unipersonal.-k. from atteindre; L. part ii., p. 78. the Carpathian Mountains; in the districts between Egypt and. qu'il, let it.-m. from suffire; L. part ii., p. 106.-. s'il Asia Minor; and between Persia and India.

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restait, if there remained; the verb is unipersonal; L. S. 84, R. 4.-0. L. S. 77, R. 2.—p. L. S. 25, R. 2.-q. faire sauter, blow up.-r. from produire; L. part ii., p. 100.—s. la retenait, sup ported it.

ANSWERS TO CORRESPONDENTS.

GEORGE ISAAC E. (Nottingham): The Italian language has no nasal sounds, and each vowel keeps its alphabetical sound irrespective of any consonant that may follow; e. g. in the words tempo, time; sento, I feel; mento, chin, the consonants m and n have no influence whatever on the pronunciation of the vowel e, such as they have in French on the pronuncis

Fre ch, is the only exception, and approaches a nasal sound. This consti

tutes an important difference between the two languages, French being to a great extent a nasal language, and Italian a language spoken from the chest. A great many examples in the first ten lessons, exclusively devoted have clearly illustrated this. The best Italian translation of the Bible, for to the explanation of the principles and mechanism of Italian pronunciation, Protestant readers, is by Giovanni Diodati. The "Society for Promoting Christian Knowledge," 67, Lincoln's-inn-fields, and the " British and Foreign Bible Society," Earl-street, New Bridge-street, Blackfriars, have both publi-hed this translation. The price varies from 3s. 8d., 4s. 8d., &c., according to the binding, and it may be had at the above-stated premises in Lincoln's-inn Fields, or at Bagster's, Paternoster-row. With regard to the Italian Dictionary, we must refer you to former remarks, and only beg to repeat that the subject will be duly considered.

ANNA PRINGLE (Ferry Hill): She must try and beat the boys in the Four Ball question; neither they nor she have mastered it yet. She is very right about fractional questions and solutions; we are proud of her corres pondence.-E. PHILLIPS (Machen): We are sorry that we can't give our correspondent the information he requires.

Le pauvre marchand voulut faire entendre raison1 au petit Bilboquet, mais il était entêté comme un cheval aveugle, et il s'engagea une dispute qui attira bientôt quelques soldats. Ils entrèrent pour s'informer du motif de la querelle, et ils trouvèrent l'idée du tambour si drôle, qu'ils obligèrent le pauvre Juif à lui céder sa barbe, et l'union of each vowel preceding them. The combination gn, pronounced as in d'eux, Gascon et perruquier du régiment, tira des rasoirs de sa poche, se mit à raser le malheureux marchands et remit solennellement la toute à Bilboquet qui l'emporta en triomphe. En arrivant au régiment, il la fit' coudre par le tailleur sur un morceau de peau d'un tambour crevé,7 et sans rien dire de son dessein, il la mit au fond de son sac. On en causas pendant quelques jours, mais il fallut bientôt penser à autre chose. On se remit en marche, et on ne pensait plus au petit Bilboquet, quand on arriva à Moscou. Alors il arriva d'affreux malheurs, le froid et la dévastation privèrent l'armée française de toutes ses ressources,19 la famine l'atteignit, et bientôt il fallut se retirer à travers un pays désert et des neiges sans fin. Je ne veux pas vous faire un tableau de cet horrible désastre ; c'est une chose trop vaste et trop épouvantable à la fois, pour que je vous en parle dans cette histoire : qu'il vous suffise de savoir que chacun s'en retournait comme il pouvait,13 et que c'est à peine s'il restait quelques régiments réunis en corps d'armée et obéissant aux généraux. Celui de Bilboquet était de ce nombre. Il était de l'arrière-garde,1 qui empêchait des milliers de Cosaques, qui suivaient la retraite de l'armée, de massacrer les malheureux soldats isolés. Un jour, ils venaient de P franchir une petite rivière, et, pour retarder la poursuite des ennemis, on avait essayé de faire sauter deux arches d'un pont de bois qu'on venait de traverser; 16 mais les tonneaux de poudre avaient été posés si precipitamment," que l'explosion ne produisit que peu d'effet les arches furent cependant démantibulées, mais toute la charpente appuyait encore sur une grosse poutre qui la retenait, et qui, si les ennemis fussent arrivés, bientôt permis de reconstruire le pont.19 COLLOQUIAL EXERCISE.

1. Le marchand chercha-t-il à | 11. le dissuader?

2. Pourquoi ne put-il lui faire entendre raison?

3. Comment les soldats trouvèrent-ils l'idée du tambour? 4. Que firent-ils ?

5. Que fit le perruquier du régiment ?

6. Le tambour parut-il content de sa prise?

7. Que fit-il de cette barbe en

arrivant ?

8. Où la plaça-t-il ensuite?
9. Parla-t-on longtemps de

cette aventure?

10. Qu'arriva-t-il à l'armée française après son entrée à Moscou?

12

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T. G. L.: The result will be most conveniently illustrated by regarding the solution as hydrochlorate of protoxide of tin: to which solution nitric acid being added, the latter becomes decomposed,-yields oxygen to the protoxide of tin, and converts it into peroxide. One portion of this peroxide is precipitated, leaving an excess of hydrochloric acid to combine with the rest. Thus the hydrochlorate of peroxide of tin results. or the acid employed was not sufficiently strong.

A. C. HILLARY: Probably the metal was not in the state of fine powder,

E. WILLIAMS: The result of such distillation would not be simply one

chemical product, but many very complex products, whose investigation

would belong to the higher departments of organic chemistry.

D. B. C. (Hartlepool): We do not answer some questions for fear of giving offence to some readers, especially when they refer to religious worship. -J. D. (Newcastle): High Dutch is German.-G. W. R. (Walnut-tree walk): The ch in archbishop is pronounced like ch in church.-MATHETES The Greek upsilon is generally replaced by y in English; as in ouv, with; astronomical day begins at the noon of one day, and terminates at the noon and in ekvens, scythes, a Scythian.-H. WATKINS (Wolverhampton): The of the next day. The civil day varies in different nations; with ourselves it begins at midnight of one day, and terminates at midnight of the next day. -G. H. H. (Haslingden): See our answer to R. S. S. (Glasgow).-A POOR STUDENT will get solutions of his questions in any treatise on Trigonometry. eût-DON QUIJOTE (Grahamston): We don't know any Spanish Dictionary about 88. or 10s. that we can recommend.-B. H. (Bristol): See page 79, vol. iii. P. E., where the rule is that things without life are neuter. Now heart and hand apart from the body are without life, and therefore strictly neuter. But by poetic gender, as it is called, sex may be attributed to these nouns in that case, we should call the heart feminine, and the hand mascu line, that is, if we were writing poetry.-HOPEFUL: Very well, go on.Socis (Liverpool) should have had an answer if his address had been

Que fut-elle bientôt obligée
de faire ?
12. Pourquoi l'auteur ne veut-il
point faire le tableau de cet
horrible désastre?

13. Que suffit-il de savoir?
14. Où se trouvait le régiment
de Bilboquet?

given.

YOUNG WHITEBREAD wishes to know the proportion in which liquor potasse must be added to sugar of lead in order to produce the potash solution of oxide of lead so useful as a test for sulphur.

A slight amount of consideration will prove to our correspondent that the proportion will altogether depend on the strength of the liquor potasse and of the lead solution. The best plan of procedure consists in disregarding 15. Que faisaient les Cosaques? solution until the desired result is accomplished. Thus, having taken some weighed or measured proportions, and adding liquor potassa to the lead 16. Qu'avait-on essayé de faire solution of acetate of lead (sugar of lead), or still better,solution of trisacetate après avoir passé la rivière? of lead (Goulard's extract), add to it by small quantities at a time liquor 17. Pourquoi l'explosion n'a-potasse until all the oxide of lead is precipitated. Then continue to add more until nearly, but not quite, all this precipitate is redissolved. By thus vait-elle pas eu beaucoup leaving a little oxide of lead, the operator is assured that liquor potasse has d'effect ?

18. Pourquoi la charpente du
pont ne tombait-elle pas?
19. Qu'est-ce que les ennemis
auraient pu faire, s'ils étaient
arrivés ?

not been added in excess.

G. H. BALDING (Hastings) wishes to know how to make crucibles for chemical experiments. He is not sufficiently precise. What sort or crucibles? and what kind of experiments? The crucible adapted for one use is totally unfitted for others. The chemist employs crucibles of clay. ware, German porcelain, blacklead-ware, iron, silver, platinum, and, 00casionally, gold; but he does not prepare those crucibles himself; they are the manufacture of various trades.

ON PHYSICS, OR NATURAL PHILOSOPHY.

No. XXII.

(Continued from page 304.)

PNEUMATIC AND HYDRAULIC MACHINES.

The Condenser.-The condenser is an apparatus which is employed to condense air or any other gas. As its form differs but little from that of the air-pump, with the exception of the valves, it will be sufficient to give here a longitudinal section of this machine, in order to show the action of the valves, which open downwards, whereas in the air-pump they open upwards. These valves, of which the one is represented at a in the bottom of the piston, and the other at o in the bottom of the barrel, fig. 103, are conical, and are kept shut by a Fig. 103.

Iwardly. These valves are kept shut by small coiled springs. The action of the valves is the same as that of the valves in the condenser; and as in the latter there is a limit to the condensation, so there is the same limit in the condensing syringe. This limit depends on the ratio which exists between the two volumes of air included under the piston, when it is at the top or at the bottom of the barrel. If the volume of air, when the piston is at the bottom of the barrel, be onesixtieth part of the volume of air when it is at the top of the barrel, we can only condense the air up to 60 atmospheres;

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coiled spring. When the piston P is raised, the air is rarefied below it, the valve o is kept shut by the spring, and the valve a opens by the pressure of the atmosphere, which permits the exterior air to enter the barrel. When the piston is lowered, the air which is below it is compressed, the valve a is shut, whilst the valve o is opened and admits the compressed air, which is transmitted to the receiver R. At every stroke of the piston, the mass of air contained in the barrel is passed into the receiver. Yet there is a limit to the tension of the condensed air; for during the condensation, a period will arrive when the elastic force of the air in the barrel, even when the piston is at the bottom, is no longer equal to that of the air in the receiver, and then no more air will pass into the latter, because the valves will remain shut, in consequence of the pressure of the interior air.

In the condenser, the tension of the air is measured by means of a small manometer of compressed air communicating with the receiver. In this machine, the receiver must be strongly fastened to the platen, otherwise it would be driven off by the elastic force of the condensed air. For this purpose, the receiver is constructed of a strong glass cylindric vessel open at both ends, and having its edges well ground and well greased. The lower edge rests on the platen A, and the upper edge is shut by a strong glass plate B, perforated at equal distances by four holes, through which pass four iron rods D, fastened to the platen. By means of these rods and the screws E, the glass plate B is firmly fixed to the cylinder, and the whole to the platen. In order to prevent accidents by the breaking of the cylinder, in consequence of the pressure of the condensed air or gas, it is surrounded by an iron grating. This machine has few practical applications; but under the following form it is of very frequent use.

for beyond that pressure, the tension of the air in the receiver K would be greater than that of the air in the barrel, and then the bottom valve would not open to give admission to an additional quantity of air.

Condensed Air Fountain.-The condensed air fountain is represented in fig. 104. It is composed of a brass cylinder K, furnished at the top with a tube and stop-cock c, upon which the condensing syringe is screwed. A tube н, open at both ends, projects to the bottom of the cylinder, or reservoir K. A quantity of water is put into this reservoir, the stop-cock c is opened, and the condensing syringe A is put in operation. The condensed air enters the reservoir by the tube H, and presses on the upper surface of the water." If then the stop-cock c be shut, and the syringe A be unscrewed, and, instead of it, a tube or ajutage be fastened to the tube н, the water will instantly issue vertically, like a spring or fountain, as soon as the stop-cock c is opened.

The apparatus in fig. 104 is also employed in the absorption of gases by water. To effect this, the stop-cock B, by means of the tube D, is made to communicate with the vessel full of gas which is to be absorbed, as, for instance, carbonic acid. The condensing syringe draws the gas from the vessel and condenses it in the reservoir K, where it is absorbed; and the Condensing Syringe.-The condensing syringe is a kind of quantity thus absorbed increases, as before observed, in proforcing pump, composed of a single barrel, a, fig. 104, of portion to the degree of condensation to which the gas is subsmall diameter, in which a solid piston (that is, a piston with-jected. By the application of a similar apparatus, aerated or out valves) is made to work by the operation of the hand. gaseous waters are manufactured.

The barrel is furnished with a screw by which it can be The Air-gun-This instrument is a gun in which the exfastened to the vessel in which the air or any gas is to be con-pansive force of condensed air forms a substitute for that of densed. Fig. 104 represents the condensing syringe A C, the gas produced by the ignition of gunpowder On the with a handle for working it, and screwed to a vessel K, in stock, which is hollow and made of wrought-iron, is screwed which the air is to be condensed. Fig. 105 shows the arrange-a force-pump, by means of which the stock may be filled with ment of the valves, which are constructed so that the side air of 10 or 15 atmospheres of pressure. A projectile being valve o opens inwardly, and the bottom valve s opens out-placed in the usual manner in the barrel, a valve communi

VOL. IV.

cating with the stock and the barrel, is opened by means of a trigger, and the air escaping from the former with great force, the projectile is discharged from the latter. The valve closing immediately that this is done, the air contained in the stock still possesses a very considerable elastic force, and several balls can be discharged without the introduction of a fresh quantity of air. The Fountain of Hero.-A variety of hydraulic machines have in modern times been constructed on the principle of Hero's fountain; such as the Hungarian machine employed for raising water from the mines of Schemnitz, the machine of Detrouville, the mechanism of Girard's lamps, &c. It is represented in fig. 106, No. 1, and is composed of three vessels; an

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in fig. 106, No. 2. In this figure D is a brass cup or vessel, and м and N are two glass globes about four or five inches in diameter; B is the long brass tube connecting the cup D with the lower part of the globe N; A is the tube connecting the upper portions of the two globes м and N. Between these two tubes is seen a third, connecting the lower part of the globe м with the atmosphere above the level of the water in D; but this tube is, in this construction, withdrawn, in order to admit of the pouring of water into the globe M, until it be half-full, This being done, the tube is replaced, and water is poured into the cup or cistern. This water descends by the tube B, into the lower globe, and drives the air out of it; this air is condensed in the upper globe, where it acts upon the water and causes it to spring up, as in the diagram. Abstracting the resistance of the air and friction, the water should rise above the cup to a height equal to the difference of the level of the water in the two globes.

The Intermittent Fountain.-The models of the intermittent fountain exhibited in our lecture-rooms explain in a plausible manner the causes of intermittent springs. The upper part of this apparatus, fig. 107, No. 1, is a close vessel or reservoir,

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upper vessel a, a middle vessel b, and a lower vessel c. These vessels are connected by three tubes: the first, a, descends from the bottom of the upper vessel, nearly to the bottom of the lower vessel; the second, y, rises from the top of the lower vessel nearly to the top of the middle vessel; and the third, z, rises nearly from the bottom of the middle vessel, and terminates in a jet a little above the upper vessel. The operation is as follows:-Water is put into the vessel b, by means of the stop-cock p, it is then closed; water is also put into the vessel a; the stop-cock r in the tube x is then opened, and the water rushes from the upper vessel into the lower one; in this vessel the water is immediately acted on by the compression of the air which it contains, and is forced up the tube y into the vessel b; here the water is again acted on by the compression of the air which this vessel contains, and is forced up the tube z, through the jet, into the atmosphere, rising to a height above the upper vessel, which, theoretically speaking, is as much above the level of the water in the middle vessel as the level of the water in the upper vessel is above the level of the water in the lower vessel. The reason is that the air which is contained in the lower vessel, and in the middle one, supports a pressure determined by a height of water equal to the difference between the two levels of the water in the upper and lower vessels; the water contained in the middle vessel must therefore rise in the tube z, to the height due to this pressure. For the purpose of lecture-room illustration, the following representation of this fountain will be better understood, as seen

filled with water up to the level ab. A vertical tube passing into this vessel from below, has its upper orifice open, and raised above the level of the liquid ab, and its lower orifice at c is also open. The bottom-piece of the apparatus is double and the orifice T allows the water which falls on the first bottom to escape into the second, A B, with less velocity than it falls from the ajutages, c, e, f, d. The flow of water from the upper vessel or reservoir continues until the water, by its accumulation, closes up the orifice, at c, of the vertical tube, and the pressure on a becomes less than the pressure of the atmosphere. This flow begins again after the discharge of a sufficient quantity of water has taken place at the orifice 1; and it continues until it is again interrupted in the same manner as before; and so on.

This apparatus is, perhaps, more vividly shown in fig. 107, No. 2, where the upper reservoir for the water is a glass globe or pear-shaped vessel, made air-tight by a ground stopper, and having two or three short capillary tubes, D, through which the water runs. A is a strong glass-tube, open at both ends, which is inserted in the globe c, having one end raised above the water-level in the globe, and the other terminating near the central orifice in the brass basin or stand B, which supports the apparatus. Here, the globe c being about two thirds full of water, this liquid issues from the orifice D, the

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