m

i s ?

T S N

up by the force of the waves breaking against the bank ; and hence,in the open sea, there is scarcely an instance of a coral-bank havingso little water that a large ship cannot pass over, but it is also soshallow that about would ground on it. [ have seen these coral-banks in all tlu: stages; some in deep water, others with few rocksappearing above the surface; some just formed into islands, with-out the least appearance of vegetation ; and others from such ashave a few weeds on the highest part, to those which are coveredwith large timber, with a bottomless sea at a pistol-shot distance.The loose coral, rolled inward by the billows in large pieces, willground; and the reflux being unable to carry them away, theybecome a bar to coagulate the sand, always found intermixed withcoral; which sand, being easiest raised, will be lodged at top.''When the sand-bank is raised by violent storms beyond the reachof common waves, it becomes a resting-place to vagrant birds,whom the search of prey draws thither. The dung, feathers, &c.increase the so.l, and prepare it for'the reception of accidentalroots, branches, and seed, cast up by the waves, or brought thitherby birds. Thus islands are formed : the leaves and rotten branchesintermixing v ith the sand, form in time a black mould, of whichin general these islands consist; more sandy and less woody ; and,when full of large trees, with a greater proportion of mould. Co-coa-nuts, continuing long in the sea without losing their vegetativepowers, are commonly to be found in such islands: particularly asthey are adapted to all soils, whether sandy, rich, or rockv. Theviolence of the waves within the tropics, must generally he direct-ed to two points, according to the monsoons. Hence the islandsformed from coral-banks must be long and narrow, and lie nearlyin a meridional direction.

ISLE ADAM, a town of France , 3 miles from Beaumont, and20 from Baris.

Isle Aumoxt, a town of France in the department of Aube , 6miles S. of Troyes .

Isi.e Jourdain, a town of France, in the department of Gers ,atid kite province of Armagnac, 8 miles N. of Lombez.

Isle Jourdain, a town of France, in the department of Vienne ,24 miles S. S. F. of Poitiers .

Isle of Beeves, a fertile island, in the Gulf of Mexico , andbay of Campeachy, 17 miles long, 8 broad, and abounding in cat-tle and fruits.

Isle of France, one of the late governments of France . Itwas hounded on the N. by Picardy, W. by Normandy , S. by theOrleaunois, and E. by Champagne.

Isle of France. See Mauritius .

ISLEBIANS, in ecclesiastical hiitory, a name given to thosewho adopted the antiscriptural senthnents of a Lutheran divine ofSaxony , called John Agricoia, a disciple and companion of Luther,a native of Isleb, whence the name; who interpreting literallysome of the precepts of St. Paul with regard to the Jewish law, de-claimed against the law and the necessity of good works.

ISLINGTON, a village of Middlesex, on the N. side of Lon-don , to which it is almost contiguous. It appears to he of Saxonorigin ; and in the conqueror’s lime was writted Isledon, or Isen-don. There is a spring of chalybeate water, in a very pleasantgarden, which for some years was constantly attended bv theprincess Amelia, and many persons of quality, who drank the wa-ters. To this place, which is called New Tunbridge Wells ,many people resort, during summer, the price of drinking thewaters being I O.v. 6d. for the seasdn. Near this, is a house ofentertainment called Sadler’s Wells, where,[during the summer-season, people are amused with romances, pantomimes, &c.

ISLIP, a tolrn of Oxfordshire,’56 miles \V. from London , notedfor the birth and baptism of Edward the Confessor .

ISMAEL. See Ishmael.

Ismael, or Ismail, a strong town of Turkey in Europe , inBessaralva, 140 miles S. by W. of Bender.

ISNARDIA, in botany, a genus of the monogynia order, andtetrandria class of plants; calyx four-cleft; corolla none ; capsulefour-celled, covered by the calyx. There is hut one species, viz.I. palustris, a creeping and floating plant; the flowers are axillary,opposite, sessile, and green. It is a native of Europe, Jamaica ,ami Virginia, in rivers.

ISNIC, or ISN IK, a town of Asiatic Turkey in Natolia . Lon.30. 9. E. Lat. 47. 15. N.

[SNY, an imperial town of Suabia , in Algow; seated on theIsny . Lon. 9. 10. E. Lat. 47. 33. N.

9

ISOCHRONAL, is applied to such vibrations of a pendulum a sare performed in the same space of time; as all the vibrations orswings of the same pendulum are, whether the arches it describesare shorter or longer. See Mechanics.

Isochronal Line, that in which a heavy body is supposed todescend without any acceleration.

ISOCRATES, one of the greatest orators of Greece , was bornat Athens , about B.C. 400. lie was the son of Theodons, who bad-enriched himself by making musical instruments, and gave Ins sona liberal education, l ie was the disciple of Prodicus, Gorgias , andother great orators, lie endeavoured at first to declaim in pub-lic, but without success; he, therefore, contented himself with in-structing his scholars, and making private orations, 'lie alwayssiiewed great love for his country ; and being informed of the lossof the battle of Cheronea, he abstained four days from eating, anddied, aged 98. There are still extant 21 of his orations, whichare admired, and have been translated from the Greek into Latin by Woltius. Isocrates excelled in the justness of his thoughts*and the elegance of his expressions. There are also nine letters at-tributed to him.

ISOETES , in botany, a genus of the natural order of filices,and eryptogumia class of plants. Anther* of the male tlower with-in the base of the frons or leaves: capsule of the female flowerbilocular, and within the base of tlu: leaf. It has two species.

ISOLA, a sea-port town of Naples, in Calabria Ultra, i5 mile 5S. E. of St. Severina. Lon 7. 33. E. Lat. 39. 1. N.

I soi.a Della Scala , a town of the late Italian republic, in thedepartment of the Mincio, and district of Verona * late provincethe Veronese, 13 miles S. of Verona .

1SOPERIM ETHICAL, [reof, equal, 7:151, about, and /j.trp*rmeasure,] in geometry, a term applied to such as have equal peri-meters, or circumferences. 1. Of isoperimetrical figures, that isthe greatest that contains the greatest number ot sides, or themost angles, and consequently a circle is the greatest of all figuresthat have the same ambit as it has. 2. Ot two isoperimetricaltriangles, having the same base, whereof two sides of one areequal, and of the other unequal, that is, the greater whose tff®sides are equal. 3. Of isoperimetrical tigures, whose sides areequal in number, that is, the greatest which is equilateral a 11 ®equiangular. From lienee follows that common problem of mak-ing the hedging or walling that will wall in one acre, or eve 11any' determinate number ot acres, or a fence or wall in any greaternumber of acres whatever. In order to the solution of this prob'lem, let the greater number be supposed a square equal to b, L et

a

x he one side of an oblong, whose area is a ; then will — be I' 1 ®a x .

other side ; and 2-}- 2 x will be the ambit of the oblong, whir®

x ft

must be equal to four times the square root of b ; that is, 2

+ 2x = 4 */b.you may makehave the same ambit,thus,

Whence the value of x may be easily had, a. n .infinite numbers of squares and oblongs A’ 3and yet shall have different given are 3 -'

Let \/ b — d,

2 a + 2 x sThen,-

= 4 cl

a + x , = 2ff.vx 1 —2 dx =—ax-— 2 d x -J- ri s = d* — ax = d' 2 — a

Thus, if one side of the square .he 10 ; and one side of an obD ri jj[he 19, and the other 1 : then will the ambits of that square a® joblong be equal, viz. each 40, ancl yet the area of the square ' vlhe 100, and of the oblong but 19. ( j

ISOPYRUM, in botany, a genus of the polygynia order, 3 ”polyandria class of plants ; natural order, Multisiliqu*. C 3 ojnone, petals five ; nectaria trifid and tubular; capsules reciii' vepolyspermous. It has three species, of no note. , , 0

ISOSC ELES TR1 ANGLE, in geometry, one that has Bequal sides. See Geometry . -jA

ISPAHAN, or, (as the Persians pronounce it,) SPAHHA™ g(| the capital of Persia , situated in the province of Irac Ags"} 1 ’^