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weight, the flexure will altogether disappear, and the string will be accurately a straight line.” In this extract, it is plainly supposed that the two points between which the “flexible string” is pulled in opposite directions, are placed in a horizontal position; if at these points, pulleys were placed and the string made to pass over both with heavy weights balanced at each extremity, it can be shown by the laws of mechanics, that the string could never be made to assume the horizontal position, until the weights were increased to infinity; indeed, Dr. Whewell, in an early edition of his “Elementary Treatise on Mechanics,” has added the following curiously-worded corollary to a problem of this kind:— “For no force, however great,

Can stretch a cord, however fine,

Into a horizontal line,

That is exactly straight.” But what learner is able to enter into the spirit of this illustration, without a much greater knowledge both of geometry and mechanics, than he can be supposed to have at the commencement of his studies? Is it necessary to go thus far for an explanation of a straight line? With all the above learned discussion, the said “flexible string,” would not be, as the writer strangely says, “accurately a straight line;" it would not in fact, be a geometrical line at all, however straight. Several other definitions of a straight line have been proposed, all of them more physical than metaphysical, that is, more dependant upon our notions of sensible objects, than upon our mental conceptions or abstractions. Plato, and long after him, Proclus, a commentator on Euclid, defines a straightline as that which viewed throughout its whole length from one extremity to the other, appears simply as a point. This is a very clever and ingenious definition; but here, you fancy you see a fellow taking up a straight line in his hand and looking at one end of it, in order to see along the whole of it to the other end of it, as if it were a ruler, or straight piece of iron. The definition of Archimedes, the prince of ancient mathematicians, is generally considered the best; viz., “A straight line is the shortest way or distance between two points.” Every one knows and understands this definition; it is the metaphysical reason of the practical fact which occasions the formation of so many footpaths across our fields from one place to another. Men reason and act geometrically, without giving their actions the name of geometry. So do bees, as we shall see further on; but these do it by instiket; those by reason. Still, even this definition is defective, great as its author really was, both as a mathematician and a philosopher. The defect is, that it does not apply to an indefinite straight line, any more than Euclid's ; it is fired between two points. Hence the necessity of Euclid's first postulate. This defect was removed by an ingenious friend of ours, whose original views of many subjects shine forth more fully developed in those of the well-known and eminent sons he has left behind him; we mean the late Thomas Wright Hill, Esq.” of Birmingham. To him are we indebted for the complete definition of a straight line which we have added to Euclid's; viz., “Astraight line is that in which, if any two points be taken, the part intercepted between them, is the shortest line that can be drawn between those points.”

The definition of a plane superficies is due to Dr. Simsen; for he

says, “instead of the definition as it is in the Greek copies, a more distinct one is given from a property of a plane superficies, which is manifestly supposed in the Elements, viz., that a straight line drawn from any point in a plane to any other point in it, is wholly in that plane.” In the edition of Euclid above referred to, this definition is ascribed to Hero of Alexandria, and it is added that Plato defined a plane surface to be one whose extremities hide all the intermediate parts, the eye being placed in its continuation. Euclid's definition of a plane superficies was similar to that of a straight line given by him, viz., that which lies evenly between its lines or boundaries. This, of course, is more objectionable even than that of a straight line. Why it is so we leave to ouringenious students to find out. In conclusion, we add that a plane superficies may be more correctly defined as that in which, if any two straightlines be taken, the part intercepted between them, is the least surface that can exist or can be supposed to exist between those lines. The distinction between a plane and a curve surface is this, that a

straight line cannot be drawn in the latter in every possible direction, whereas in the former it can. A straight line cannot be drawn on the surface of a sphere; it may be drawn on the surface of a cylinder or cone in one direction, but not in every possible direction. QUESTIONs on THE PRECEDING LEsson.

Give Dr. Simson's explanation of a point; of a line; of a surface; and of a solid. What is defective in Euclid's definition of a straight line P. What is Playfair's definition of a straight line, adopted in Dr. Thomson's edition R. Give some idea of the attempts to deduce the definition of a straight line from physical notions. Why does a flexible string over pulleys placed in a horizontal line, and stretched by equal weights at each end, fail to represent a straight line : What is the definition of a straight line given by Plato an Proclus? What is the definition of it given by Archimedes What is the improvement made in this definition by Mr. Hill 2

(To be continued.)

L ES SONS IN LAT IN.—No. XVIII, By John R. BBARD, D.D. REGULAR WERBS. T H E FI as T C o N J U GAT 1 on. Active voice. ExAMPLE.-Amo, I love. Chief Parts; amo, amávi, amátum, amáre. Characteristic letter, A long, PARTs witH THE correspond ING ENGLISH.

IND. PREs. SUB. PRES. IND. IMP. SUB. IMP. Latin. arrio athern amábum . amárem English. I love I may love I did love, I might I do love, or or love I am loving Iwasloving I. Furt. II. FuT. Jatin, amábo anávero English. I shall or I shall have will love loved IND. Peter. sub. PERF. Inp. PLUPERP SUB. Plupportr Latin. amávi amāverin amáveram amavissem English. I have loved I may have I had loved I might have loved loved In F. PREs. Latin. amáre English. to love I. Sur. II. Sup. PART. Pries. FUT. PART. Act. Latin. amátum amátu amáns amatārus English. to love to be loted loviny about to love GER. GER, GER. GER. INF. Perr. Latin, amandi amando amandum amando amavisse English. of loring to loving loving by loving to have loved In F. FuT. IMP. Latin, amatārum esse arria English. to be about to love love thou

Before I proceed I will explain these contractions:

* The father of Rowland H.II, Esq., the inventor of the Penny Postage scheme; of M. D. Hill, Esq., Q.C., and Recorder of Birmingham; of Frederick Hill, Esq., Government Inspector of Prisons; of Edwin Hill, Esq., Superintendent of the Postage Stamp Department; and of Arthur Hill, Esq., Conductor of Bruce Castle School, Tottenham.

Contractions. IND PREs. SUB. PREs.
Explanation.—Indicative Mood, Present Subjunctive Mood, Present
Tense, Tense.
Contractions. IND. I.M.P. SUB. IMP.
Explanation.—Indicative Mood, Imperfect Subjunctive Mood, Imper-
Tense. Jęct Tense.
Contractions. I, FUT. II. FuT. Ind. PERP.
Explanation.—First Future Second Future Indicative Mood,
Tense, Tense, Perfect Tense.
Contractions. sub. Pert. IND PLUPERF.
Explanation.—Subjunctive Mood, Perfect Indicative Mood, Pluper-
Tense. stct Tense.
Contractions. SUB Pitreof. INF. PREs.
Explanation.—Subjunctive Mood, Pluper- Infinitive Mood, Present
fect Tenge. Tense,
Contractions. INr. PEnr. Ixp. Fut. IMP.
Explanation.—Infinitive Mood, Per- Infinitive Mood, Imperative
fect Tense. Future Tense. Afood,

Contractions. I. SUp. II. Sup. Pres. PART. Explanation.—First Supine. Second Supine. Present Participle. Contractions. FUT, PART. ACT. GER. Explanation.-Future Participle, Active Voice. The Gerund.

Having in the above corresponding parts given the Latin as well as the English of several members of the verb, I need not repeat them. I supply in full what remains. As I write for young men and women rather than for children, I omit adding the English in all the detail of the persons; for when you know what is the first person, you will readily supply the rest; thus, if the English of amaveram, the first person, is I had loved, you know that the English of amaveras, the second person, is thou hadst loved, and of amaverat, the third person, he had loved; so also in the plural,

Instead of I might have loved, the sub. pluperf. may sometimes be rendered (put into English) by I would, I should, or 1 could have loved.

In the corresponding English words, I have 5. the nearest approach to the several Latin parts. The student will do well to adhere strictly to these meanings at the first, though, as the correspondence between the several Latin and the several English parts is not entirely complete and constant, he will find occasions when his English will appear scarcely idiomatic, or strictly proper. He cannot, however, learn too soon, that in few particulars are any two languages exactly correspondent. Accordingly, for amo, I have set down what may be termed three meanings, namely, I love, I do love, and I am loring. Here, it is obvious that the English is more rich than the Latin, inasmuch as it has three forms of the present tense indicative mood, while the Latin has but one form. Having but one form, the Latin cannot by a form indicate the variations of the English present tense. Consequently here is a want of strict correspondence; and here also is a source of doubt; for we may ask, what is the English equivalent of amo? is it, I love, or I do love, or I am loving f

After these remarks the student will know that it is with

some latitude that he is to take these
Cornesponding LATIN AND ENGLISH SIGNs.
IND. PREs. SUB. PREs. IND, IMP. SUB.IMP. I. FUT. II, FUT.
Jat. o ena bam rein bo ero
Eng. do may did might will will have
Ixp. PER. SUB.PER. IND. Plupport. Sub. PlupeR. INP. PRE8.
Lat. i erim erani issem are
Eng. have may have had might have to
INF. PERF.—Latin. isse English. to have.
INr. Fur. IMP. I. SUP. II. Sup, PART. PREs, FUT. PART. Act.
Lut, rum esse ama una u arts rus
Eng. about to do in order to to ing on the point of

Give yourself a thorough practice in these signs. Again and again ask, until you are perfect, what is the English sign of the indicative mood present tense? what the Latin sign? what is the Latin sign of the sub. pluperf. what the English sign of the same? Šo go through all the parts. I hope you understand what I mean by these signs. Your understanding of them is the more important because they pertain not merely to the verb amo, or to the first conjugation, but to all the verbs; and because, when you are perfect in your knowledge of them as just given, you will easily put atin into English and English into Latin. On the account of this importance, I will subjoin a few explanations: These signs, then, might be called a set of equivalents, and I might have indicated them after this manner:

i - have bo - will erim - may have

These signs or equivalents are, you see, without any verb. They are so given because they are applicable to all verbs. Thus to i you prefix the stem amav, and make amavi ; so to hare you add 1 and lored, and make the corresponding English, that is, the English equivalent of amavi, namely, I hate lored. In some instances the English sign is arbitrary, or the best we can get; in the ind. pres, love is chosen, as the E.S. (English sign) for the want ..? a better. Scarcely less arbitrary the E. S. of the imp., -namely, did. -

These departures from exact correspondence, preeision, and uniformity are certainly drawbacks; but, notwithstandin these drawbacks, great aid may be derived from a careful an systematic attention to the system here set forth. I have said that these signs are applicable to all verbs. If so, they need not be repeated. And in general the statement is correct. You will, however, bear in mind what you have reviously learnt as to the tense-endings, and the mood-endings; and then you will remember that instead of bo, am, es, &c.) is the ending, and as the ending so the sign of the first ture of the third and the fourth conjugations. One or two other deviations will oceur to you.

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ExAMPLEs.-Like this model, conjugate laudo 1, I praise; curo 1, I take care of; vocol, I call.

Compare together the II. Fut, with the Sub. Pres. You will find that the endings are the same, except, in the first person, which in the former is ro, in the latter rim. In other words, the Latin language has no distinctive form beyond the first person for one or the other of these tenses. A distinction is attempted with the aid of the accent or the quantity. Thus the first person plural of the second future is sometimes pronounced long, as amaversmus. But the authority for this is not uniform, and consequently you find the sign of the long and the sign of the short vowei thus : over the is denoting that the vowel is sometimes pronounced with and sometimes without the accent.

Ts Ama-(ri)sti pronounced amavisti, as one word; the vi is put in brackets to denote that it may by syncopation (shortenino) be omitted; as afterwards explained. - -

There is a difference between the first future, amabo, and the future formed with the aid of the future participle, thus, amaturus sum. Amabo means I will or shall love, simply indicating a future act, without determining when, or the precise point in the future when the act will take place. Amaturus sum signifies I am about to love, -that is, I shall shortly love; intimating that the action signified in the verb is near at hand, is in the immediate future.

Of the first future there is properly no subjunctive tense; the import, however, is expressed § combination, thus, amaturus sim (sis, sit, &c.), I may be about to love; amaturus essem, I might be about to love. The second future also is without a subjunctive mood.

ExERcises.—Form according to the model now given, that is, write them out in full, with all the parts in both Latin and English, these verbs,-laudo I, I praise; vigilo l, I watch; compárol, I procure.

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The quantity of matter which volcanic fires abstract from the bowels of the earth, and throw up to the surface is enormous. It has been scientifically calculated, that a volcano has, in some instances, thrown up, even at a single eruption, more matter than if the entire mountain had been melted down to yield the supply. The question which must interest every geologistis, “Where does all this mass of matter come from ?" Among the various productions of volcanoes may be enumerated, gases, aqueous vapours, lava, minerals, scorine, stones, ashes, sand, water, and mud. It is well known that volcanoes emit different kinds of gases, such as muriatic gas, sulphur combined with oxygen or with hydrogen, carbonic acid gas, and nitrogen, besides aqueous oradours. everal of the simple minerals, and some of the metals are found in the melted materials ejected by volcanoes, such as common salt, chloride of iron, sulphate of soda, muriate and sulphate of potassa, iron, copper, lead, arsenic, and selenium. he examination of these gases and minerals belong rather to chemistry than to geology. They are related to geology only as they give aid in the study of the mineral character of rocks. From the very nature of such mineral productions it was to be expected that volcanic substances, should greatly vary in lithological character, from that of light ashes to that of compact and heavy crystalline rock. Nor is it a wonder that the quantity of mineral matter ejected is so great as it is, especially when you consider what a multiplicity of elementary substances are acted upon by the fires below, and how these elements in their fused state, strive to combine with each other in different ways and proportions. It has been ascertained that, within three square miles around Vesuvius, more specimens of the simple minerals have been found than on any other spot of the same dimensions. Of the 380 different species of minerals known to the celebrated Haüy, 82 had been found on Wesuvius alone. Lava is a name given to any mineral matter melted in a volcano, and ejected in a stream over the rim of the crater. When the molten lava is consolidated by cooling, it receives fresh names, partly according to its mineral composition, and artly according to the slowness or rapidity of its refrigeration. ence such names as scoriae, cinders, pumice, basalt, trachyte, obsidian, &c. The melted lava may be boiling for years within the walls or cliffs of a crater, as has been represented in fig. 11 and fig. 15, without flowing over its edges. When lava swells above the edges of a crater, and flows down the declivities of the hill, it does not spread itself on all sides as a flood of water would, but it moves in a tall half-rounded mass, not very unlike the engravings that you have seen of a tubular bridge. The sides of this moving body of lava harden so as to form something

like two walls; and its upper surface also hardens, so as, with the two sides, to form a kind of tunnel through which the burning or incandescent matter flows. This peculiarity of the walls of a lava current is well known in Italy, and by this knowledge men are able to deflect the burning stream, and to turn it aside from its intended course. The people make a gash in one of the hardened sides of the current. At this gash the lava will issue out, and discontinue the course which it threatened to take. By this method man villages and towns have been saved from the destruction whi menaced them. An instance of this took place in Italy a few years ago. The people of Campania saw a current of lava descending from Vesuvius which was likely to overwhelm their hamlet. ey immediately went up to meet the fiery stream; attacked it on the side farthest from their direction, and turned the current towards Paterno. When the inhabitants of Paterno heard of this manoeuvre, they took up arms, arrested the operation, and caused the burning tide to take its own course. As such a hardened crust is a good non-conductor of heat, the melted matter within it takes a long time to cool. The lava which flowed from Etna in 1819, was, nine months after the eruption, in a state sufficiently fluid or molten, to move at the rate of a yard a day. There is an instance, in the same mountain, of lava being in perceptible motion even ten years after the eruption. This deserves your notice, on account of a very remarkable fact, and a fact which may help to resolve some difficult problems in the examination of ancient rocks. In 1828 a large mass of ice, several hundred square yards in extent, was found in Mount AEtna lying under a bed of lava, which had covered it while flowing in a melted state. . How could this be? You can imagine that rain-water, or drifted snow, might freeze into a glacier at the elevation of ten thousand feet, which was the height at which this ice was found. This bed of ice was formed in a large hollow, while the volcano was in a state of rest. But, when the burning lava flowed over the ice, how is it that the ice did not melt 2. It is probable that the bed of ice had been previously covered by a thick shower of volcanic ashes. As such a layer of ashes is also a good non-conductor of heat, it prevented the ice from melting: and after the bed of lava had cooled over it, it continued to preserve the ice in an unmelted state. The truth of this theory is established by facts which occur about AEtna in the present day. In the higher regions of that mountain, the shepherds, in order to provide a supply of water for their flocks during summer, are in the habit of sprinkling beds of snow with a layer of volcanic sand, a few inches thick, and this is found to be an effectual means of preventing the sun from melting until it is wanted. The term scorize or cinders, is applied to the fragmentary slags of lava which are ejected into the air, and then settle around the volcano. The structure of these cinders is owing entirely to the influence of the external air, and not to any special difference of material in composition. Whether lava flows like a stream, or is thrown up in jets, it cracks and becomes porous, as soon as it is acted upon by the atmospheric gases. The result is, that the pieces or fragments become cellular or vesicular, that is, a mass full of small rounded holes, as may be seen in any specimens of pumice and lava: If lava is cooled under great pressure, it becomes compact, and even crystalline as in trap, trachyte, &c. During an eruption, masses of stone are frequently thrown up into the air. Where do these stones come from, and come unmelted When the little islet, called Graham's Island, rose in the Mediterranean, near the coast of Sicily, in 1831, its crater ejected pieces of dolomite rock, and fragments of limestone; and also masses of some pounds weight of Silurian lock. In the awful eruption of Tomboro, in Sumbawa, an island in the Molucca group, which took place in 1815, stones fell very thick—some of them as large as two fists, but most of them only of the size of a walnut. In a museum at Naples, are exhibited specimens of the various stones which have been ejected from the crater of Wesuvius. Several of these specimens are fragments of the limestone which prevails in the district, and these limestone specimens contain organic remains in them. These specimens prove that the vent of the volcano goes lower down than the limestone bed, and that the melted matter thrown up rubs against the sides of this rock, rends and tears portions of it off, and throws them up into the surface. These limestone specimens are found to be impregnated with magnesia, an element which entered it while it was being heated in this volcanic crucible. In fig. 20, you see how the vent of a crater passes through various beds of rock, such as A, B, C, D, E, F, some of which are fossiliferous, and others are of the more ancient class. The upper stratum, A B, is formed by the ejected matter which has been thrown up on all sides from the volcano. Besides stones, it is found that volcanoes discharge a vast quantity of Ashes, which darken the air for hours, and sometimes for many days, and which in their fall occasion great damage to agriculture, and to villages and

Fig. 20.

gistin accounting for the bones and skeletons of extinct species of animals which are found in the ashes of ancient volcanoes, such as are found in Avergne, in France. Many naturalists think that it was by such a shower of ashes that Pompeii and Herculaneum were destroyed, and that this accounts for the perfect preservation of even the most ile articles found amid those fossil cities. ome remarkable facts connected with the structure of these ashes deserve to be noticed. When Graham Island rose in the Mediterranean, in 1831, Dr. Davy mentions a shower of ashes which fell. In the substance of these ashes, he found fibres like vegetable fibre, and which had

towns. These dry and hot ashes are

robably only ava pulverised

the smell of a burning seaweed, This has led to the conjecture that as sea-water entered

or turned into powder by friction. It has been conjectured by some that they

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the submarine volcano, fibres of weeds were sucked in with it.

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have once rested on the surface of the incandescent matter while cooling under diminished pressure. ese ashes are sometimes like impalpable powder, but, in other instances, very heavy as a mass. During the eruption of Tomboro, in Sumbawa, in 1815, the ashes which fell, were so heavy as to crush and destroy several houses even at forty miles distance from the crater. Also at sea, to the west of Sumatra, some thousand miles off from Tomboro, the ashes and cinders fell so thick as to float two feet deep on the surface of the sea, and render the passage of ships extremely difficult. In other instances, the ashes were so light and subtile as that, notwithstanding an awning made to cover the deck, they lay in heaps of a foot in depth on many parts of the vessel, and several tons were thrown overboard. The quantity of ashes discharged by volcanoes must be immense. In 1835 there was an eruption of Cosiguiana, a volcano in the gulf of Fonseca, on the shores of the Pacific. During that eruption, ashes fell at Truxillo, on the shores of the Gulf of Mexico. Portions of this shower of ashes fell on board a ship twelve hundred miles westward of the volcano, and four days later at Kingston, in Jamaica, 700 miles eastward of it, having travelled in the airby an upper current of west wind, at the rate of 170 miles a day. For about 30 miles to the south of this volcano, ashes covered the ground three yards and a half deep. Thousands of cattle, wild animals, and birds perished under the ashes. This fact assists the geolo

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Mud volcanoes, as seen by Humb

The vent of a volcano passing through various strata, and wearing away fragments jrom the sides of the rocks.

Sept. 2, 1845, a Danish ship was sailingin{1°north laulu-e, a thick cloud was seen to approach the vessel from the N. W. in the direction of Iceland. The sails and the deck were immediately covered with ashes. These ashes had come from the volcano, Mount Hecla, which was in a state of eruption on that day. This volcano was 533 miles from the ship, so that the ashes must have travelled at the rate of 46 miles per hour. The famous Professor Ehrenberg examined this dust under a powerful microscope, and discovered that it abounded in wellknown siliceous organic bodies, and in well preserved shells or cases of infusoria. This is a fact of great importance, as it .. us to account for certain volcanic dust found near extinct volcanoes such as the Eifel, on the Rhine.

There are volcanoes which eject water,... or whose craters are filled with it. The greatee part of the vapour discharged by volcanoes is purely aqueous. It is this vapour when condensed by cold air that forms the springs which are on the sides of volcanic mountains, But, besides this aqueous vapour, there are cases in which - water is a volcanic product. It has been argued by many that water acts an important part in the eruptions of volcanoes, since, of 300 volcanoes on the globe, two-thirds are situated in islands, and the greater part of the other third are either on the borders of the sea, or not far from the coast. There are, however, some volcanoes, such as those in Mexico and in Central Asia, which are very far from the sea,

oldt at Turbaco, in New Grenada.

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Near Seminara, in Calabria, an earthquake opened a chasm in which a lake was formed 1785 feet long, and 937 broad. It was called Lago del Tolfilo. The inhabitants of the district, from fear that the miasma from such a lake would be prejudicial to their health, tried to drain off its waters by means of canals. Their work proved vain, for the lake was found to be constantly filling from springs which issued at the bottom of the chasm. In 1811 the volcanic island, afterwards called the Sabrina, was observed to rise from the sea near St. Michael, at the Azores. Its crater shot up cinders 700 or 800 feet above the level of the sea. These cinders were followed by an immense column of smoke. It began to rise in June. On the 4th of July it was high enough above the sea to form an island about a mile round. In its centre was a crater full of hot water, which discharged itself over one of the edges into the sea. One of the most singular products of a volcano is MUD. When the aqueous vapours from the crater are condensed by the cold atmosphere, heavy rains are produced, which fall upon the volcanic dust on the sides of the mountain, and form a current of mud called by the Italians “lava d'aqua,” or aqueous lava, an enemy much more dreaded than a stream of melted lava. It is disputed by some geologists whether it was not by such a flood of volcanic mud, rather than by volcanic showers, that Pompeii was destroyed. This, * or, is only mud on the surface of volcanoes. In some volcanic districts mud is found to ooze occasionally from the ground. Near Laureana in Calabria, the swampy soil of two ravines became filled with calcareous matter, which oozed out of their respective sides just before the shock of an earthquake was felt in that district. This mud flowing downward from both ravines, at last became united, formed one stream, increased in force, and was a mud river 225 feet wide and 15 feet deep. In its progress it overflowed a flock of goats, and tore up trees, which it carried on its bosom like the masts of small boats. When the mud became dry it was reduced in depth to about seven feet, and it was found to contain fragments of earth of iron colour. I have now to call your attention to a real mud volcano, as represented by Von Humboldt, see fig. 21. Near Carthagena, in New Grenada, South America, there is a high hill called Popa. To the south-west of this hill there is a village district called Turbaco. In the midst of a thicket of palms is a marshy ground called Los Volcancitos. The tradition of the inhabitants is, that this ground was once all in flames, but that the fire had been extinguished by a monk who sprinkled the place with holy water. Since then the fire volcano has become a watery one. The volcaneitos are about 15 or 20 in number, stand in cones from 19 to 25 feet high, and measure around their bases from 78 to 85 feet each. On the top of each of these volcancitos is an aperture or depression from 15 to 30 inches in diameter, and filled with water, through which air-bubbles are constantly escaping, as seen in fig. 21. In other parts of the ground there are apertures for such escape of air, but which are not surrounded by cones. The cones have, no doubt, been raised by the clayey mud contained in the fluids, and the dull sound, which precedes every ebullition in the water of the cone, indicates that the ground is hollow. It seems that each crater receives its supply of air and gas from separate channels. These little craters are always filled with water, even in the driest seasons. The temperature of the water is not higher than that of the atmosphere. These mud volcanoes originate with earthquakes, and their rise is accompanied with subterranean detonations and with jets of flame. Their diminished action supplies us with a specimen of the perpetual though subdued activity of the interior of the earth. The muddy water seems at the first ebullition to have been of a high temperature, but afterwards the temperature becomes lower. This fact implies that the vents, which at first communicated with deep-lying strata of great heat, have, by some means, become obstructed or choked up, and that the vents of the cooler water do not rise from any great depth below the surface. These mud volcanoes are found in different parts of the globe. In the Caspian Sea, on the peninsula of Abscheron, is situated the mud volcano of Jokmali. It was formed November 27, 1827. At first flames sprang up from the soil, and

blazed to a great height for three hours. Then, for about twenty-four hours, they continued to burn about three feet above the crater from which the mud was ejected. Near a village called Baklichi the flame rose so high as to be seen twenty-four miles off. Large fragments of rock were thrown to a great distance round. These, as we have seen in fig. 20, must have been torn from the cavities of the strata beneath. At Damak, in the province of Samarang, in the island of Java, there is a similar mud volcano, where the mud is of high tem. erature. At Girgenti, in Sicily, and at Sassueto, in Northern taly, they are also found under the name of Salses,

LESSONS IN ENGLISH.—No. XI. By John R. BEARD, D.D DERIVATION: PREFIXES (continued).

Beyone proceeding further with these prefixes we may now expose a common error. It is generally thought that words have severa disconnected significations. Several significations many words have, but these significations are all allied one with another. And they are allied one with another in such a way that a genealogical connexion runs through them all. I mean that the second ensues from the first, and conducts to the third. The meanings of words flow from a common source like the waters of a brook. That common source, or parent-signification, is, in all cases, one that denotes some object of sense, for objects of sense were named before other objects. Our first duty then is to ascertain the physical meaning of a word. From that meaning the other meanings flow as by natural derivation. Those secondary or derivative significations then can scarcely be termed meanings; they are not so much meanings as modifications of the primary import of the root. Certainly they are not independent significations . Thus viewed, words have not two or more senses, but in the several cases the one sense is varied and modified. Even in instances in which opposite meanings are connected with the same word, the filiation may be traced, as both Jacob and Esau sprang from the same stock. I will take an example in the word prevent, Prevent means both to guide and to hinder, to lead to, and to debar from. The opposition is sufficiently decided. Yet these two opposed meanings are only modifications of the root-sense of the word. First, I will exhibit the diversity and then explain it. Prevent, signifying to guide, aid forward:— “Prevent us, O Lord, by thy grace—“Book of Common Prayer.” “— Love celestial whose prevenient aid

Forbids approaching ill.” Malief. Prevent, signifying to hinder, obstruct. “Where our prevention ends, danger begins." Caretc.

“Which though it be a natural preventive to some evils, yet without either stop or moderation, must needs exhaust his spirits.”—Relig. Wottonianae,

“Physick is either curative or preventive; preventive we call that which preventeth sickness in the healthy.”—Brown, “Vulgar Errors.”

“Prevent us, O Lord, by thy grace,” means “aid us forward.” “Preventive of sickness,” signifies that which causes sickness not to come. There is the contrariety. Now for the explanation. Prevent is made up of two Latin words,-namely, prae, before, and venio, I come or go. Now, you may go before a person for two opposite purposes. You may go before him in order to guide, aid, and conduct him onward; or you may go before him to bar up his way, to hold him back, to prevent his advance. And as either of these two purposes is prominent in the mind of the speaker, so the word is used by him to signify, to guide, or to hinder. The proper meaning, then, of prevent is, to come before: hence, l, to guide, or, as a natural consequence, 2, to aid; or again, l, to obstruct, and as a natural con-equence, 2, to stop, &c. And how the moral and spiritual imports come out of the physical, is also seen in the diverse applications of the word; for, as we have just read of preventive medicine, so in divinity you may read of “preveaase of grace.”

These remarks, illustrations of which occur in what has just preceded, and will occur in what is about to follow, may serve to show you that language must be studied genealogically. Indeed every word has a history; and in the dictionaries, every account

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