F-12/V2+W. F-V=0;

them in channels to fertilize as great an extent of land as possible. In China and in India, as well as in Egypt, infrom which it would seem that we might find F, and then genious modes of watering lands have been adopted from G. But on examining this last equation we find it to be the most remote ages. No expense has been thought too precisely that kind of cubic equation about which the diffi- great to secure a supply of water, and to distribute it in the culty arose; for the P of this equation is negative, being most advantageous manner. It seems that where there is − ~ (V2 + W2), and the Q is - V; and P3, being great heat in the air, water alone will supply the necessary −À (Va+W2), is numerically greater than Q, or V. food for the growth of plants. It is probable that the comWhence this case is called irreducible; for though, as will ponent parts of the atmosphere are more easily separated, be shown immediately, there are three possible values of and made to enter into new combinations with those of the expression (3), yet every direct algebraical attempt to water, in a high temperature than in a lower; or that the find them leads to the same difficulty in another form. 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 pally as stimulants or re-agents, and are themselves comdiffused through the water. Manures seem to act principosed 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.

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)
−¦(1−√−3) (F+G√−i) −} (1+√−3) (F-G-1)
for the other admissible values. These may be reduced to
-F+G/3, and F-G3,
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 - 21x + 200. Here P=21, Q20, ¿ Q2 + 1⁄2 Ï3 = -243-81X3. Hence the roots are contained in

{− 10 + 9 √3 √−1}} + { −10—9√3 √=1}3

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 is in the hands of every tyro, namely, the tables of sines and recourse to a registry of the roots of cubic equations, which cosines, by which also the theorem of Bombelli will be established, 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). Ássume V = r cos. 0, W= r sin. 0, or find r and 0 from

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 cos. 40 sin. 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. 0; the three values of which, obtained as just noted, are

2 1/r. cos. 10, 2 /r cos. (120°+10), 2 /r cos. (240°+10) which may be thus written:

2 r. cos. 10, -2/r. cos. (60°-10), −2/r. cos. (60°+10.) Thus, in the preceding example, which gives V=-10, W=9/3, we find r2=100+243-343-7; whence /r -7. And tan. 0 = −√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 27, 27, 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

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 Hence we can readily suppose that the mere great measure must be ascribed the fertilizing effects of pure and soft running water.

purpose.

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 pears to be as necessary as its presence; and, provided there be a sufficient supply of water of a proper quality, the more 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 irriga tion, 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 partial state of decomposition is added to this water, it will accurate notion of the system. much improve its quality, and by a judicious distribution We shall suppose a river to run with a rapid current of it over the land a great benefit may be obtained. between high banks. At some point of its course a portion If there is not a want of water, there may be a want of deof the water is diverted into a canal dug along the bank, clivity to enable it to flow off, which, it should always be with a very small declivity. The water in this canal will remembered, is an essential part of irrigation. Art may flow with less rapidity than the river, but will keep the in this case assist nature by forming a passage for the water, same level as that part of the river where it has its origin. either in its course towards the land to be irrigated, or from Thus the water may be carried over lands which are situated it after it has effected its purpose. Where there is no natural considerably above the bed of the river farther down. All exit, and it might lead to too great an expense to make an the lands between this canal and the river may be irrigated artificial one, the water may sometimes be led into shallow if there is a sufficient supply of water. The canal may be ponds, where a great part is evaporated; or porous strata carried to a considerable distance from the river. The size may be found by boring, into which it can be made to run and of the canal and its declivity depend on the quantity of water be dispersed. Along rivers where the fall is very impercepwhich may be made to flow into it. A dam is often constructed tible à channel brought from a considerable distance may across a river, in order that as much of its water as is pos- give such a command as to throw the water over a great sible may be diverted, and the original channel is often laid extent of surface; and to carry it off another channel may quite dry, to take advantage of all the water at the time be cut, emptying itself at some distance below: so that when it is advantageous to irrigate the land. To have an | lands which lie along the banks of a river may be irrigated. entire command of the water there are flood-gates on the although they are actually below the level of the river, and main channel and on the lesser branches. By opening or require banks to protect them from inundation. 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.

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 of 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 sides 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 profirst 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 receives the water and distributes it lower down, until the last pours it into the river. This is called catch work, because the water is caught from one channel to another. This method is only applicable where there is a considerable fall of water and a gentle declivity towards the river. But it must be borne in mind that the water is deteriorated for the purpose of irrigation, when it has passed over the land, and that it is not advantageous to let it flow over a great extent when a fresh supply can be obtained: but where only a small portion of water can be commanded, that must be made the most of; and it will irrigate three or four portions of land in succession without there being any very marked difference in the effect: beyond this it rapidly loses its fertilizing qualities. This is not owing to the water having deposited the fertilizing substances which it held in solution, or which were diffused through it, but it is owing to its having taken up some which are detrimental to vegetation, and being saturated with them: at least this is the most probable opinion when all circumstances are taken into the account.

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 difliculty 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

grow as long as the water flows over it. Too much moisture however would be injurious, and the meadows are therefore laid dry by shutting the flood gates, whenever the temperature of the air is above freezing. By this management the grass grows rapidly at the first sign of spring. Before the day upland meadows have recovered the effects of frost and begun to vegetate, the herbage of the water-meadows is already luxuriant. As soon as they are fed off or cut for the first crop of hay, the water is immediately put on again, but for a shorter time; for the warmer the air, the less time will the grass bear to be covered with water. A renewed growth soon appears, and the grass is ready to be cut a second time when the dry meadows only give their first crop. Thus, by judicious management, three or four crops of grass are obtained in each season, or only one abundant crop is made into hay, and the sheep and cattle feed off the others. The usual way in which the grass of water-meadows is made profitable is by feeding ewes which have early lambs till the middle of April. A short flooding soon reproduces 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 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

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 ex-
perience, 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
effects depend on entirely different causes. When low
meadows are inundated in winter and spring, it is the mud-
diness of the water which enriches the land: a fine layer of I
extremely divided matter is deposited, and when the water
subsides this acts as a coat of manure.

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 as much for a month as a later crop would for the remainder 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 beginning of May; and after that it may be cut repeatedly during the summer. But where the soil is good and the 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 watermeadow 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 watermeadow 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 all kinds of soils may be converted into fertile watermeadows. 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 must 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 fed off. In summer the floodings must be very short; 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

banks. In this case the grass, which has not yet sprung | Irvine, m 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 be 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.]

ISABELLA of CASTILE. [COLUMBUS; FERDINAND V. ISEUS, one of the ten Athenian orators, was a native of Chalcis, or, according to other accounts, of Athens. Dionysius 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, who 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 preceding plan (fig. 1) will explain what has been briefly said respecting the different modes of irrigating land. AA is a 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. The author of the Life of Isæus, attributed to Plutarch, This channel is carried round a hill and supplies a series of mentions sixty-four orations of Isæus, fifty of which were channels, C, C, C, placed below each other, forming catch- allowed to be genuine. At present there are only eleven work along a declivity. A portion of the water goes on to D, extant, all of which are of the forensic class (Xóyoi dikawhere it supplies the feeders of a regular set of ridges, or vuxoi), and all treat of matters relating to wills and the beds, made as before described, from which the water succession to the property of testators, or persons intestate, returns into the river by a main trench, into which all the or to disputes originating in such matters. These orations drains run. are valuable for the insight which they give us into the On the other side of the river, where the slopes lie some-laws of Athens as to the disposition of property by will, and what differently, there are several examples of catch-work, in cases of intestacy, and also as to many of the forms of the black lines representing the drains which receive the procedure. Dionysius, in his laboured comparison between water after it has flowed over the surface and carry it into Lysias and Isæus, sums up as follows:-'In reading Lysias the river below. It is evident that all the feeders are one would not suppose that any thing is said either in an nearly horizontal, to allow the water to flow over their artificial manner or without perfect sincerity, but everysides. 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 seems to aim at truth, but Isæus to follow art: the one strives to please, the other to produce effect.'

Fig. 2.

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.

Dionysius adds that, in his opinion, with Isæus originated that vigour and energy of style (davórns) which his pupil 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 judgment

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 Isaus we feel that we have to do with a subtle disputant 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 Milan, 1815, by Ang. Mai. The translation of Isæus by Sir William Jones (1779, 4to.) will give an English reader a sufficient notion of this orator; but the translation is somewhat deficient in critical accuracy, and also wanting in force.

ISAIAH (TY, LXX. 'Heatas), 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 Diny, 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, BC. 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