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F-1 V+ Wa . F − }V =0;

from which it would seem that we might find F, and then G. But on examining this last equation we find it to be precisely that kind of cubic equation about which the difficulty arose; for the P of this equation is negative, being − ̃2/ (V2 + W), and the Q is - V; and P3, being (V+W), is numerically greater than Q, or V Whence this case is called irreducible; for though, as will be shown immediately, there are three possible values of the expression (3), yet every direct algebraical attempt to find them leads to the same difficulty in another form.

If F and G could be determined, one value of (3) is 2 F; and taking the other cube roots, selecting only those pairs whose products are possible, we find

−} (1+√−3) (F+G√−i) −¦(1−√/−3) (F-G√1) -4 (1-3) (F+G√−i) −↓ (1+√−3) (F— GA/− 1) for the other admissible values. These may be reduced to -F+G/3, and -F-G√3,

which are both possible. Consequently, the irreducible case of a cubic equation is that in which the three roots are all possible.

Let us apply the preceding to -212x+20=0. Here P = 21, Q = 20, Q2+1, P3 = −243-81X3. Hence

the roots are contained in

{− 10 +9√/3 √−1}' + {−10−9√3 √=1}b.

By trial (or by semi-tentative methods, described in most books of algebra) it may be found that a cube root of 10+9√√√1 is 2+√√√√1; whence F2, G 3. Hence one root (2 F) is 4; the second and third (F+G√3 and -F-G/3), are −2+3 and -2-3, or 1

and -5.

=

But the best method of obtaining the roots is by having recourse to a registry of the roots of cubic equations, which is in the hands of every tyro, namely, the tables of sines and cosines, by which also the theorem of Bombelli will be esta blished, namely, that the difficulty of the irreducible case answers to that of the trisection of an angle in geometry. It is proposed then, by means of trigonometry, to calculate the values of (3). Assume V cos. 0, W=r sin. 0, or

find r and 0 from

r = √V2+W2,

=3

W tan. 0= V

in which that sign must be given to r, which gives r cos. the sign of V. Then, by De Moivre's theorem [NEGATIVE AND IMPOSSIBLE QUANTITIES],

(cos. 0 ± sin 0√/− 1) = cos. §0 ± sin. 40 √−1, in which, by substituting 0+360° or 0+720° for 0, the equation tan. 0=V÷W is still satisfied, and while the first side of the preceding equation is not altered in appearance, the different values of the cube root appear on the second side. From this we readily find that the expression (3) is no other than 22/r. cos. 10; the three values of which, obtained as just noted, are

2 3/r. cos. 10, 2 2/r cos. (120°+30), 2 /r cos. (240°+10) which may be thus written:

22 r. cos. 10, -2 2/r. cos. (60°-39), -2 r. cos. (60°+}0.) Thus, in the preceding example, which gives V=-10, W=9/3, we find r2=100+243-343-7; whence /r

√7. And tan. = −√3, whence is found to be -(57° 19′ 16′′),one-third of which is-(19° 6′ 25′′), and this, with 79° 6' 25" and 40° 53′ 35′′, are the angles on which the required values depend. The cosines of these angles, severally multiplied by -2/7, 2/7, and 2/7, give results as near to -5, 1, and 4 (the values found), as the unavoidable errors in the last places of logarithmic results, and the preceding rejection of fractions of seconds, will permit.

IRRIGATION. Of all the substances which concur in the vegetation and growth of plants water is the most essential without moisture the seed cannot germinate, nor can the plant receive nourishment. Hence in warm climates, where rains are periodical, and where the soil is dried and parched by a continued evaporation, no verdure exists, except where springs or rivers supply the waste of moisture. The warmer the climate, and the more rapid the evaporation, the more luxuriant is the vegetation, provided there be an abundant supply of water. This circumstance has suggested the plan of diverting streams and conducting

them in channels to fertilize as great an extent of land as possible. In China and in India, as well as in Egypt, ingenious modes of watering lands have been adopted from the most remote ages. No expense has been thought too great to secure a supply of water, and to distribute it in the most advantageous manner. It seems that where there is great heat in the air, water alone will supply the necessary food for the growth of plants. It is probable that the component parts of the atmosphere are more easily separated, and made to enter into new combinations with those of water, in a high temperature than in a lower; or that the leaves and green parts of vegetables imbibe water in a state of solution in air, and that in this state it is more easily decomposed. Atmospheric air and water contain all the principal elements of vegetables, viz. oxygen, hydrogen, carbon, and nitrogen; the remainder are either found in the soil or diffused through the water. Manures seem to act principally as stimulants or re-agents, and are themselves composed of the same elements: they are of no use unless diffused or dissolved in water; but when the water is impregnated with animal or vegetable substances, the effect is far greater and more rapid than when the water is pure.

Water has also an important office to perform, if we admit the principle discovered by Macaire, that plants reject through their roots those portions of the sap which are the residue of its elaboration, and which are of no further use to the plant, but rather injurious if they are again imbibed by the roots. Plants seem to require a removal of their excrements, as animals do when tied up in stalls, or confined in a small space. If this is not effected, they suffer and contract diseases. The percolation of water through the soil is the means which nature has provided for this washing of the roots has a beneficial effect, and to this in a purpose. Hence we can readily suppose that the mere great measure must be ascribed the fertilizing effects of pure and soft running water.

matter held in solution remains in the soil, all the advantage If water stagnates and is evaporated, and the noxious of irrigation is lost, and the better kinds of grasses are sucin all marshy spots. The circulation of the water therefore apceeded by rushes and coarse aquatic plants, as may be seen be a sufficient supply of water of a proper quality, the more pears to be as necessary as its presence; and, provided there porous the soil, and especially the subsoil, is, the more vigorous is the vegetation. It is on this principle alone that we can rationally account for the great advantage of irrigation in those climates where rain is abundant, and where the soil, which is most benefited by having a supply of water running through it, is of a nature to require artificial draining as an indispensable preliminary to being made fertile by irrigation. By keeping these principles in view great light will be thrown on the practical part of irrigafion, which, having been long established by experience before these principles were thought of, depends not on their correctness, but only confirms their truth.

The whole art of irrigation may be deduced from two simple rules, which are, first, to give a sufficient supply of water during all the time the plants are growing, and secondly, never to allow it to accumulate so long as to stagnate. We shall see hereafter one apparent exception to this last rule, but it will be readily explained.

The supply of water must come from natural lakes and rivers, or from artificial wells and ponds, in which it is collected in sufficient quantity to disperse it over a certain surface. As the water must flow over the land, or in channels through it, the supply must be above the level of the land to be irrigated. This is generally the principal object to be considered. If no water can be conducted to a reservoir above the level of the land, it cannot be irrigated. But there must also be a ready exit for the water, and therefore the land must not be so low as the natural level of the common receptacle of the waters, whether it be a lake or the sea, to which they run. The taking of the level is therefore the first step towards an attempt to irrigate any lands.

Along the banks of running streams nature points out the declivity. A channel, which receives the water at a point higher than that to which the river flows, may be dug with a much smaller declivity than that of the bed of the river, and made to carry the water much higher than the natural banks. It may thence be distributed so as to descend slowly and water a considerable extent of ground in its way to rejoin the stream. This is by far the most common mode of irrigation, and the shape, size, and direction

of the channels are regulated by the nature of the surface when it would not be of much use to the land, it may be and other circumstances, which vary in almost every situa- kept in ponds, and it will lose none of its qualities by being tion. A few examples will give to those who are not ac-exposed to the air. If animal or vegetable matter in a quainted with the best modes of irrigating land a pretty accurate notion of the system.

We shall suppose a river to run with a rapid current between high banks. At some point of its course a portion of the water is diverted into a canal dug along the bank, with a very small declivity. The water in this canal will flow with less rapidity than the river, but will keep the same level as that part of the river where it has its origin. Thus the water may be carried over lands which are situated considerably above the bed of the river farther down. All the lands between this canal and the river may be irrigated if there is a sufficient supply of water. The canal may be carried to a considerable distance from the river. The size of the canal and its declivity depend on the quantity of water which may be made to flow into it. A dam is often constructed across a river, in order that as much of its water as is possible may be diverted, and the original channel is often laid quite dry, to take advantage of all the water at the time when it is advantageous to irrigate the land. To have an entire command of the water there are flood-gates on the main channel and on the lesser branches. By opening or shutting these the water may be stopped or made to flow as may be required. It must be remembered, that to carry water to a considerable distance, and in great quantity, a larger channel and more rapid declivity are required; and it is a matter of calculation whether it is most advantageous to bring a smaller quantity to a higher point, or a greater abundance somewhat lower. Having a certain command of water, it may be carried from the main channel by smaller branches to different points, so as to irrigate the whole equally. These branches should be nearly horizontal, that the water may overflow the sides of them, and be equally distributed over the land immediately below. Every branch which brings water over the land should have a corresponding channel below to carry it off; for the water must never be allowed to stop and stagnate. When it has run 15 or 20 feet, according to the declivity, over the land situated below the feeder, or the channel which brings the water, it should be collected into a drain to be carried off, unless it can be used to irrigate lands which lie still lower. Finally it runs back into the river from which it was taken, at a lower point of its course.

partial state of decomposition is added to this water, it will
much improve its quality, and by a judicious distribution
of it over the land a great benefit may be obtained.
If there is not a want of water, there may be a want of de
clivity to enable it to flow off, which, it should always b
remembered, is an essential part of irrigation. Art may
in this case assist nature by forming a passage for the water,
either in its course towards the land to be irrigated, or from
it after it has effected its purpose. Where there is no natural
exit, and it might lead to too great an expense to make as
artificial one, the water may sometimes be led into shallow
ponds, where a great part is evaporated; or porous strate
may be found by boring, into which it can be made to run and
be dispersed. Along rivers where the fall is very impercep
tible a channel brought from a considerable distance may
give such a command as to throw the water over a great
extent of surface; and to carry it off another channel may
be cut, emptying itself at some distance below: so tha
lands which lie along the banks of a river may be irrigated.
although they are actually below the level of the river, and
require banks to protect them from inundation.

When the surface to be irrigated is very flat and nearly
level, it is necessary to form artificial slopes for the water to
run over. The whole of the ground is laid in broad beds,
undulating like the waves of the sea. The upper part of
these beds is quite level from end to end, and here the
channel or float which brings the water on is cut. From
the edge of this channel the ground is made to slope a foot
or two on both sides, and a ditch is cut at the botttom
parallel to the float. The whole of the ground is laid out in
these beds. All the floats are supplied by a main channel
at right angles to the beds, and somewhat above them, and
all the ditches or drains run into a main ditch parallel to
the main float, and below the lowest drain.
The course o
the water is very regular. As soon as the flood-gates are
opened it flows into all the upper channels, which it fills
till they overflow in their whole length. The sloping side
are covered with a thin sheet of running water, which the
lower drains collect and carry into the main ditch.

Experience has shown that there are particular seasons when the water has the best effect; a perfect command of it is therefore indispensable, and also a regular supply When there is a considerable fall and a sufficient supply During frost, when all dry meadows are in a state of torpor of water, a series of channels may be made, so situated be- and the vegetation is suspended, the water-meadows, having low each other, that the second collects the water which the a current of water continually flowing over them, are pro first has supplied, and in its turn becomes a feeder to irri-tected from the effect of frost, and the grass will continue to gate the lower parts of the declivity: a third channel re- grow as long as the water flows over it. Too much moisture: ceives the water and distributes it lower down, until the however would be injurious, and the meadows are therefore last pours it into the river. This is called catch work, be- laid dry by shutting the flood gates, whenever the temperacause the water is caught from one channel to another. ture of the air is above freezing. By this management the This method is only applicable where there is a considerable grass grows rapidly at the first sign of spring. Before the dry fall of water and a gentle declivity towards the river. But upland meadows have recovered the effects of frost and it must be borne in mind that the water is deteriorated for the begun to vegetate, the herbage of the water-meadows is purpose of irrigation, when it has passed over the land, and already luxuriant. As soon as they are fed off or cut for the that it is not advantageous to let it flow over a great extent first crop of hay, the water is immediately put on again, but when a fresh supply can be obtained: but where only a for a shorter time; for the warmer the air, the less time wil small portion of water can be commanded, that must be the grass bear to be covered with water. A renewed growth made the most of; and it will irrigate three or four portions soon appears, and the grass is ready to be cut a second of land in succession without there being any very marked time when the dry meadows only give their first crop. difference in the effect: beyond this it rapidly loses its fer- Thus, by judicious management, three or four crops of tilizing qualities. This is not owing to the water having grass are obtained in each season, or only one abundant deposited the fertilizing substances which it held in solution, crop is made into hay, and the sheep and cattle feed off the or which were diffused through it, but it is owing to its having others. The usual way in which the grass of water-mcataken up some which are detrimental to vegetation, and being dows is made profitable is by feeding ewes which have early saturated with them: at least this is the most probable lambs till the middle of April. A short flooding soon reproopinion when all circumstances are taken into the account. duces a crop, which is mown for hay in June; another flooding gives an abundant aftermath, which is either mown for hay, or fed off by cows, bullocks, and horses; for at this time the sheep, if pastured in water-meadows, are very subject to the rot. The value of good water-meadows could scarcely be believed by those who are not familiar with them. Where the water is suited to irrigation they never require manuring. Their fertility is kept up continually. and the only attention required is to weed out coarse aquatic plants, which are neither nutritious nor wholesome in hay or pasture.

The general principle of irrigation may be described as the supplying every portion of the surface with an abundance of water, and taking it off again rapidly. In many situations the great difficulty in irrigation arises from the want of a supply of water; but even then a partial irrigation may be effected, which, although not perfect, will have its advantages. A small rill which is often quite dry in summer may still, by judicious management, be made to improve a considerable portion of land: its waters may be collected and allowed to accumulate in a pond or reservoir, and let out occasionally, so that none be lost or run to waste. If there is but a small quantity it must be husbanded and made to flow over as great a surface as possible. If there is water only at particular seasons of the year, and at a time

The best soil for a water-meadow is a good gravel. The finest water-meadows on the Avon in Wiltshire, where the richest herbage is found, have scarcely any soil at all, but are on a bed of shingle and pebbles matted together by the

IRR

roots of the grass, which proves to demonstration that the waters of the Avon contain all the principles essential to rapid vegetation. Great attention is required, and some experience, to irrigate meadows, so as to give the greatest profit. In hot weather, when we should imagine that the land must be thirsty, and that too much water cannot be poured over it, much mischief may be done by injudicious flooding. In winter, on the contrary, the land may be covered with water for weeks without injury; and if an earthy deposit takes place, the subsequent fertility is greatly increased. But this is not properly irrigation: it is inundation, and the When low effects depend on entirely different causes. Ineadows are inundated in winter and spring, it is the muddiness of the water which enriches the land: a fine layer of extremely divided matter is deposited, and when the water subsides this acts as a coat of manure.

41

Water may be carried in small channels through meadows without being allowed to overflow, and in this case the effect is similar to that caused by rivers or brooks which wind slowly through valleys, and produce a rich verdure along their course. This is watering, but not properly irrigating. When this is done judiciously, the effect is very nearly the same as when the land is irrigated; and in hot climates it may be preferable, by giving a constant supply of moisture to the roots, while the plants are growing. The great advantage of water-meadows in England is not so much the superior quantity of grass or hay which is obtained when they are mown, as the early feed in spring, when all kinds of nutritive fodder are scarce; when the turnips are consumed before the natural grass or the rye sown for that purpose is fit to be fed off, the water-meadows afford abundant pasture to ewes and lambs, which by this means are brought to an early market. The farmer who has watermeadows can put his ewes earlier to the ram, without fear of wanting food for them and their lambs in March, which is the most trying season of the year for those who have sheep. At that time an acre of good grass may be worth f as much for a month as a later crop would for the remainder is of the year. When it is intended to form a water-meadow on a surface which is nearly level, or where a fall of only two or three feet can be obtained in a considerable length, the whole of the land must be laid in beds about 20 or 30 feet wide, the middle or crown of these beds being on a level with the main feeders, and the bottoms or drains on a level with the lower exit of the water, or a little above it. To form these beds most expeditiously, if the ground is already in grass, the sod may be paired off and relaid after the beds are formed, by which means the grass will be sooner re-established; but except in very heavy soils, where the grass is some time in taking root, the easiest and cheapest way is to plough the land two or three times towards the centre, and dig out the drain with the spade: the earth out of the drains, and that which is taken out of the upper trench or feeder, may be spread over the bed to give it the proper slope. A roller passed over the bed in the direction of its length will lay it even, and the seeds of grasses being Sown over it, the water may be let on for a very short time

to make them spring. As soon as the grass is two or three
inches above ground a regular flooding may be given, and
in a very short time the sward will be complete. Instead
of sowing seed, tufts of grass cut from old sward may be
spread over the newly formed beds, and they will soon
cover the ground. The Italian rye-grass, which has been
lately introduced into this country from Lombardy and
Switzerland, grows so rapidly, that if it be sown in February,
or as soon as the snow and frost are gone, it will afford a
good crop to feed off in April, or to mow for hay by the
But where the soil is good and the
beginning of May; and after that it may be cut repeatedly
during the summer.
water abundant, good natural grasses will spring up without
much sowing, and soon equal the old water-meadows.
It seems essential to the formation of a good water-meadow
that the bottom be porous and free from stagnant water;
hence under-draining is often indispensable before a water-
meadow can be established; and a peat-bog, if drained
and consolidated, may have water carried over its surface,
and produce very good herbage. If the soil is a very stiff
clay, draining is almost indispensable where a water-
meadow is to be made. The more porous the soil the less
depth of water is required, which is not obvious at first
sight; but the clay lets the water run over the surface
without soaking into the roots, whereas the porous soil is
soon soaked to a considerable depth. The water must
therefore be longer on the clay than on the sand or gravel
to produce the same effect. If the water is properly applied
meadows.
all kinds of soils may be converted into fertile water-

On very stiff clays a coat of sand or gravel, where it can be easily put on, will greatly improve the herbage. It should not be ploughed in, but laid on the surface two or three inches thick: chalk will also improve the herbage.

The usual time of letting on the water on water-meadows is just before Christmas, and it may continue to flow over the land as long as the frost lasts: in mild weather it may be turned off during the day and put on again at night until the frost is gone. The grass will soon begin to grow, and be ready to be fed off. When this is done the water is immediately let on for a short time, and turned off again to allow the ground to dry after a few days' flooding, and the water is let on again at short intervals. The warmer the air is, the shorter time inust the water be allowed to cover the meadows. As soon as the grass is five or six inches long it must be left dry entirely till it is mown or In summer the floodings must be very short; fed off. seldom more than twenty-four hours at a time, but frequent. Thus a great weight of grass may be obtained year after year without any manure being put on the land, care being taken that where the surface is not quite even the hollows be filled up with earth brought from another place, or dug out of the drain, if that should be partially filled up with the soil which the water has carried into it. We alluded before to a case where water may remain a considerabie time on the land without injury; this is, when there are inundations from rivers, which rise above their beds in spring and cover the low meadows which lie along their

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P. C., No. 793.

VOL. XIII-G

banks. In this case the grass, which has not yet sprung | Irvine, in union with Rothsay, Inverary, Campbelltown, up, is protected from the cold, and if there is a deposit from and Ayr, returns one member to parliament. The school, the water there is a considerable advantage. But when it wherein Greek, Latin, French, and the mathematics are subsides, it must be made to run off entirely, without taught, is ably conducted by the rector and an English leaving small pools, by which the grass would invariably be assistant. The population of the burgh and parish of injured. Small ditches or channels are usually dug, by Irvine in 1831 was 5200. (Carlisle's Dictionary; Beauties which all the water may run off, unless where the subsoil of Scotland; Population Returns, &c.) is very porous, or the land is well under-drained, which is seldom the case in these low meadows, for the drains woul he apt to be choaked by the earthy deposit from the water. These inundations can sometimes be regulated by means or' dykes and flood-gates, in which case they partake of the advantages of irrigation, and also of that deposition of fertilizing mud which is called warping. [WARPING.]

The preceding plan (fig. 1) will explain what has been briefly said respecting the different modes of irrigating land. A A is river which has a considerable fall, and then flows through a level plain. A considerable channel is cut at B, where there is a rapid fall over a natural or artificial dam. This channel is carried round a hill and supplies a series of channels, C, C, C, placed below each other, forming catchwork along a declivity. A portion of the water goes on to D, where it supplies the feeders of a regular set of ridges, or beds, made as before described, from which the water returns into the river by a main trench, into which all the drains run.

On the other side of the river, where the slopes lie somewhat differently, there are several examples of catch-work, the black lines representing the drains which receive the water after it has flowed over the surface and carry it into the river below. It is evident that all the feeders are nearly horizontal, to allow the water to flow over their Fig. 2.

sides.

b

Fig. 2 is the section of catch-work. a, a, are the feeders; b, the drain; c, c, c, c, intermediate channels which act as feeders and drains.

Fig. 3.
b

Ridge-work.

ISABELLA of CASTILE. [COLUMBUS; FERDINAND VỊ ISEUS, one of the ten Athenian orators, was a native of Chalcis, or, according to other accounts, of Athens. Dienysius could not ascertain the time of his birth or death. So much as this appears certain: the vigour of his talent belonged to the period after the Peloponnesian war, and he lived to see the time of king Philip. Hermippus, whe wrote the lives of the pupils of Isocrates, has recorded nothing more of Isæus than that he was a pupil of Isocrates, instructed Demosthenes, and enjoyed the society of the chief philosophers of his time.

The author of the Life of Isæus, attributed to Plutarch mentions sixty-four orations of Isæus, fifty of which were allowed to be genuine. At present there are only eleven extant, all of which are of the forensic class (Móyou diavicoi), and all treat of matters relating to wills and the succession to the property of testators, or persons intestate, or to disputes originating in such matters. These oration are valuable for the insight which they give us into the laws of Athens as to the disposition of property by will, and in cases of intestacy, and also as to many of the forms of procedure. Dionysius, in his laboured comparison between Lysias and Isæus, sums up as follows:-'In reading Lysis one would not suppose that any thing is said either in an artificial manner or without perfect sincerity, but every thing appears natural and true; thus forgetting that it is the height of art to imitate nature. In reading Isæus one has just the contrary feeling; nothing appears to be spoken naturally and without an effort, not even what really is so spoken; but everything seems of set purpose, framed to deceive, or for some other sinister end. One would believe Lysias, though he were stating what was false. one cannot, without some feeling of distrust, assent to Isæus even when he speaks the truth.' Again:- Lysias seem to aim at truth, but Isæus to follow art: the one strives t please, the other to produce effect.'

Dionysius adds that, in his opinion, with Isæus originate that vigour and energy of style (davórne) which his pup Demosthenes carried to perfection. So far as the extant spe

Fig 3 is the section of two adjoining ridges. a, a, the feeders; b.b, b, the cimens of Isæus enable us to form an opinion, this judgmen

drains.

Fig. 4.

Fig. 4 is a sluice to regulate the flow of water IRRITABILITY. [HALLER.] IRTISCH. [SIBERIA.] IRVINE, a royal borough and seaport town in the district of Cunningham and county of Ayr, 68 miles southwest by west from Edinburgh. It is situated on a rising ground to the north of the river Irvine, and about half a mile distant from the harbour, which lies to the south-west of it. The town is dry and well aired, and consists of one broad street, which communicates with the southern suburb by means of a narrow stone bridge of four arches, rebuilt in the year 1826. The principal public buildings are the church and town-house. The harbour is commodious, having from nine to eleven feet water on the bar at spring-tides; though during violent gales from the south it rises to sixteen feet. The rapid growth of Kilmarnock has tended greatly to increase the trade of Irvine, which is the nearest seaport to that town. The dues levied at the port during the five years preceding 1832 averaged 4507. per annum. Ship-building is carried on upon a small scale.

appears to be just. The perspicuity and the artless simplicity of the style of Lysias are admirable; but on reading Isæus we feel that we have to do with a subtle disputan and a close reasoner, whose arguments are strong and pointed, but have too much the appearance of studied effect, and for that reason often fail to convince.

The best edition of the text of Isæus is by Bekker. The oration on the 'Inheritance of Menecles' was first published by Tyrwhitt, London, 1785; and that on the ' Inheritance of Cleonymus' first appeared in its complete form at Miian, 1815, by Ang. Mai. The translation of Isæus by Sir William Jones (1779, 4to.) will give an English reader a suthcient notion of this orator; but the translation is somewhat deficient in critical accuracy, and also wanting in force.

ISAIAH (TY, LXX. 'Hratas), one of the most cele brated of the Hebrew prophets, lived during the reigns of Uzziah, Jotham, Ahaz, and Hezekiah (Is. i. 1; vii. 1; xiv. 28; xxii.; xxxvi.-xxxviii.), and was contemporary with the prophets Amos, Hosea, Joel, and Micah. We possess no particulars in the Old Testament respecting the place of his birth or his history; but we learn from the inscription of the book that he was the son of Amoz, who was, according to one Jewish tradition, the brother of Amaziah, king of Judah; but according to another was considered to be the same person as the prophet Amos. The latter tradition is evidently wrong; since the name of the prophet is Diy while the name of the father of Isaiah is . It is probable, from the 6th chapter of the book, that Isaiah entered upon his prophetical office in the last year of the reign of king Uzziah, B.C. 759. He continued to prophesy at least till the fourteenth year of the reign of Hezekiah, B.C. 713 (2 Kings, xix. 2-7; Is. xxxvi.—xxxviii.), a period of fortysix years. According to an antient Jewish tradition, which is also given in the apocryphal book of the 'Ascension of

Isaiah,' he was put to death during the reign of the cruel Manasseh (2 Kings, xxi. 16); who is said by Josephus (Antiq., x. 3, § 1) to have slain all the prophets in Jerusalem. Manasseh commenced his reign B.C. 697; and Isaiah must therefore have continued to prophesy for sixtytwo years at least, if this tradition is correct. Isaiah had a greater influence in public affairs than any other prophet, except Elijah and Elisha. He appears to have been the intimate friend of Hezekiah; and it was principally owing to his advice and firmness that the army of Sennacherib was defeated.

The prophecies of Isaiah consist of sixty-six chapters, all of which were considered, till within the last thirty or forty years, to have been composed by the prophet himself. But it is the common opinion of the critics in Germany usually called Rationalists, that the book of Isaiah is a collection of prophecies delivered by different persons, which were collected and arranged in their present form during the Babylonian exile. The whole of the latter part of the book, from ch. xl. to ch. lxvi., is supposed to have been written at Babylon during the exile, and a considerable part of the first thirty-nine chapters is attributed to other authors than Isaiah. Some critics have called the book a 'poetical anthology. This opinion was first maintained by Koppe, and has been supported by Döderlein, Justi, Eichhorn, Bauer, Paulus, Rosenmüller, Bertholdt, De Wette, Augusti, and at great length by Gesenius in his translation of Isaiah, Leip., 1821-9. The best arguments in defence of the common opinion are given by Jahn in his 'Introduction to the Bible, by Professor Lee in his Sermons and Dissertations on the Study of the Scriptures,' and by Hengstenberg in his 'Christologie des alten Testaments,' Berl., 1829-35. If we admit Isaiah to have been the author of the book which bears his name, it is nearly certain that the prophecies are not arranged at present in the order in which they were delivered. The sixth chapter apparently contains an account of the inauguration of the prophet in his sacred office, and appears to have been the first prophecy that was published by him. The twenty-second chapter consists of two separate parts which have no connexion with each other, and were probably published at different times; the former half of the chapter (1-14) containing a prediction of the invasion of the Medes and Persians, while the latter half gives an account of the disgrace of a courtier of the name of Shebna during the reign of Hezekiah. It is therefore difficult to give any connected account of the contents of the book; but the following arrangement, taken from Gesenius, is perhaps the best upon the whole.

The first part (i-xii.) principally consists of prophecies relating immediately to the Jewish people; the second part (xiii.-xxiii.) contains predictions against the Babylonians, Assyrians, Philistines, Moabites, Syrians, Egyptians, and other foreign orations; the third part (xxiv.—xxxv.), with an historical appendix (xxxvi.-xxxviii.) containing an account of the invasion of Sennacherib, contains prophecies of the invasion of Judæa by the Babylonians, of the destruction of Jerusalem, the captivity of the people, and their final restoration to their native country; the fourth part (xl.-lxvi.) principally refers to the restoration of the church; it contains many prophecies respecting the deliverance of the Jews from captivity, the destruction of idols, the spread of the true religion over the earth, the conversion of the Gentiles, and the coming of the Messiah.

The prophecies of Isaiah have always been held in great veneration by the Jews. Jesus, the son of Sirach, speaks of Isaiah as 'a prophet great and faithful in his vision, who saw by an excellent spirit what should come to pass at the last, and comforted them that mourned in Sion. He showed what should come to pass for ever, and secret things before they came. (Ecclesiasticus, xlviii. 22-25.) Josephus and Philo frequently speak of Isaiah in terms of the greatest respect; and his prophecies are constantly quoted by the writers of the New Testament. See Matt. i. 22, 23, compared with I. vii. 14; Matt. iii. 3, with Is. xl. 3; Matt. iv. 14-16, with Is, ix. 1, 2; xlii. 7; Matt. viii. 17, with Is. liii. 4; Matt. xiii. 14, 15, with Is. vi. 9, 10; Matt. xxi. 13, with Is. lvi. 7; Luke, iv. 17-19, with Is. lxi. 1-3; Acts, xiii. 34, with Is. lv. 3; Acts, xxviii. 25-27, with Is. vi. 9, 10; Rom. ix. 27, 28, with Is. x. 22; Rom. ix. 29, with Is. i. 9; Rom. ix. 33, with Is. viii. 14; Rom. x. 16, with Is. liii. 1; Rom. x. 20, 21, with Is. lxv. 1, 2; 1 Cor. i. 19, 20, with Is. xliv. 25; 2 Peter, iii. 13, with Is. lxv. 17.

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A considerable part of the prophecies of Isaiah are supposed by most Christian divines to relate to the Messiah. The following list is taken from Gray's Key to the Old Testament,' pp. 369, 370: the divine character of Christ (vii. 14; ix. 6; xxxv. 4; xl. 5, 9, 10; xlii. 6-8; lxi. 1; Ixii. 11; lxiii. 1-4); his miracles (xxxv. 5, 6); his peculiar qualities and virtues (ix. 2, 3; xl. 11; xliii. 1-3); his rejection (vi. 9-12; viii. 14, 15; liii. 3); his sufferings for the sins of man (liii. 4-11); his death, burial (liii. 8, 9), and victory over death (xxxv. 8; liii. 10-12); his final glory (xlix. 7, 22, 23; lii. 13-15; liii. 4, 5), and the establishment, increase (ii. 2-4; ix. 7; xlii. 4; xlvi. 13), and perfection (ix. 2-7; xi. 4-10; xvi. 5; xxix. 18-24; xxxii. 1; xl. 4, 5; xlix. 9-13 ; li. 3-6; lii. 6-10; lv. 1-3; lix. 16-21; Ix.; lxi. 1-5; lxv. 25) of his kingdom. The number of Isaiah's prophecies relating to the Messiah was thought by Jerome to be so numerous and important, that he says, in his preface to the book, that Isaiah ought rather to be called an Evangelist than a prophet; and many modern commentators give him the title of the Evangelical Prophet. The style of Isaiah is said by Lowth (Prælect. xxi.) 'to abound in such transcendent excellencies, that he may be properly said to afford the most perfect model of the prophetic poetry. He is at once elegant and sublime, forcible and ornamented; he unites energy with copiousness, and dignity with variety. In his sentiments there is uncommon elevation and majesty; in his imagery the utmost propriety, elegance, dignity, and diversity; in his language, uncommon beauty and energy; and notwithstanding the obscurity of his subjects, a surprising degree of clearness and simplicity. To these we may add that there is such sweetness.in the poetical composition of his sentences, whether it proceed from art or genius, that if the Hebrew poetry at present is possessed of any remains of its native grace and harmony, we shall chiefly find them in the writings of Isaiah.'

In addition to the book of prophecies, Isaiah is also said to have written the lives of Uzziah (2 Chron. xxvi. 22) and Hezekiah (2 Chron. xxxii. 32). The former work is entirely lost; but we probably possess the greater part, if not the whole, of the latter in chapters xxxvi.-xxxviii. of his prophecies.

We learn from the Fathers that several aprocryphal works [APOCALYPSE], which were in circulation in the early ages of the Christian æra, were attributed to Isaiah. An Ethiopic translation of one of these works, entitled the 'Ascension of Isaiah,' which was originally written in Greek and is quoted by Epiphanius (Hæres. xl. 2) and Jerome (Commentary upon Is. lxiv. 4), was published for the first time by Dr. Laurence, Oxf. 1819, 8vo. This work contains an account of the prophet's ascension through the firmament and the six heavens into the seventh, and also of his martyrdom during the reign of Manasseh.

(The Introductions of Eichhorn, Jahn, De Wette, Augusti, and Horne; Vitringa, Commentarius in Librum Proph. Isaic, 2 vols. fol. 1714-1720; Lowth's Isaiah, Lond. 1778, frequently reprinted; there is a good German trans'ation of this work with many additions by Koppe, 4 vols. 1779-1781; Döderlein's Esaias, 8vo., 3rd ed., 1789, with excellent notes; Rosenmüller's Scholia; Gesenius, Der Prophet Jesaia, übersetzt und mit einem vollständigen philologisch-critischen und historischen Commentar begleitet, Leip. 1821-9, the best translation and commentary that has yet appeared.)

IS'CHIA, the antient Ænaria, an island situated at the northern entrance of the Bay of Naples, the smaller island of Procida lying between it and the promontory of Misenum on the mainland. Procida (Prochyta), according to an old tradition, was rent from Ischia by an earthquake. The island is mountainous; the highest summit, called Mount Epomeo, which is an extinct volcano, rises about 2500 feet above the sea, and has near its summit distinct traces of two very large craters. The volcanic district of Naples is considered to comprise not only Vesuvius, with Pozzuoli and Cumæ, but also the islands of Procida and Ischia. The last eruption of the Epomeo was in 1301, when a broad stream of lava ran over the eastern part of the island, for nearly two miles, as far as the sea. Strabo calls this island by the name of Pithecusa, which is not, as Pliny observes, derived from pithecus (an ape), but from a word of similar form, which signifies an earthen vessel. The clay of the island, it seems, has been used for earthenware from the remotest time. The island was settled by Greeks of Chalcis and Eretria. There were numerous traditions of volcanic

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