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on account of the difunion of its particles ; but thefe par- ticles coming clofer together, and uniting as the water freezes, light, expanfive, and elaftic air-bubbles are thus generated, and increafe in bulk as the cold grows ftronger ; whence of courfe the Ice grows lighter, and thefe air-bubbles acquiring an elaftic force burft to pieces any veflel in which the water is clofely contained. But fnow-water, or any water long boiled over the fire, affords an Ice more folid than ordi- nary, and with fewer bubbles. This alio freezes much flow- er than common water j whereas, on the contrary, pure wa- ter long kept in vacuo and frozen afterwards there, freezes much fooner, on being expofed to the fame degree of cold,; than water unpurged of its air and fet in the open atmo- fphere. And the Ice made of water thus diverted of its air, is much harder, more folid and tranfparent, and more pon- derous than common Ice. Boerb. Chem. P. I. p. 376. 7"o make the molt perfect Ice we fhould take the pureff. wa- ter, and perfectly purge it of its air by the air-pump; then irecze it in the fevereft froft, by means of Mr. Farenheit's contrivance. Thus we obtain an Ice of the greateft hard- nefs, denfity, purity, tranfparence, and gravity. In the mountains of Swiflerland there are immenfe maffes of Ice, which by the tradition and hiftorics of the country znuft have lain there for many centuries. At certain times there happen cracks in thefe, and by thefe cracks the vaft thicknefs of the maffes may in fome meafure be guefied at ; fome of them being three or four hundred ells deep, and yet none of them ever having gone through the whole thicknefs. Wagner's, Hift. Nat. Helv. The vaft bodies of Ice met with in the northern feas near Hudfon's-Bay, are furprifing ; fome of them being immerfed an hundred fathoms or more under the the furface of the ocean, and a fifth or fixth part above, and three or four miles in circumference. See Phil. Tranf. N° 465. Sect. 2. Thefe floating mountains of Ice owe their vaft bignefs and durable nature to a caufe not confidered by many ; that is, to their not being common Ice, but the ice of fea-water ; many experiments proving, that in acid and fpirituous li- quors, when the froft has power over them, the watery parts only are affected, and the Ice is taftelefs, while the liquor re- mains concentrated, and much ftronger than before at the bottom, or in the center. It was generally fuppofed that the faline liquors, and confequently fea-water, were affected by freezing in the fame manner ; that is, its watery part alone was frozen, and the fait feparated from the part fo congealed ; but Dr. Lifter has proved, that the Ice formed of fea-water is really fait, and does contain fea-falt, and fi- nally that it is, by means of this fait contained in it, ren- dered more durable than common Ice, If a vial of falt- water be expofed to the air in frofty weather till flakes of Ice are found in it, and then brought into a warm room, thofe flakes will remain even in that place a long time un- diflblved ; and if they are taken out and expofed at a fmall diftance to the fire, they will not run into water as common Ice would, but they will by degrees evaporate, and there will be left only a little white fait.
Since fea-water when frozen thus forms a very durable Ice, it appears eafy to conceive, that the immenfe maffes of fuch Ice found in the northern feas fhould continue undiflblved through the whole year, and at the return of the freezing feafon remaining of the fame bignefs as at firft, they muft of confequence then become much bigger by the freezing of more Ice about them ; and thus continuing to Iofe very little, and that only by accidents, and annually to increafe a great deal, it is not wonderful that they become fo large. Philof. Tranf. N° 167. p. 836.
lcz-Pfa?it, a very Angular and beautiful plant of the Ficoides kind, called by Mr. Tournefort, Ficoides afrhana folio plan- tagenu undulato micis argenteis adfperfo, or the African Fi- coides with a wav'd plantain-like leaf, and covered with filver drops. It is alfo commonly called with us the diamond- plant, and the froft-plant, from its leaves and flalks being all over befetwith tranfparent cryftal-like drops, as if cover- ed over with fmall icicles. The feeds of this plant are to be fbwn very early in the fpring upon a good hot bed ; when the plants are come up they are to be tranfplanted into fmall pots filled with frefh light fandy earth, and plunged into an- other hot bed ; as that hot bed declines in heat they fhould be moved into a third, and this will bring them forward to- ward flowering. In July thefe plants may be expofed by de- grees to the open air, and foon after this their flowers will appear. If it is dented to have thefe plants very large, they fhould be fhook out of their pots into an old hot bed of tanners bark, in which their roots will extend every way, and the branches in proportion ; fo that a fingle plant will fometimes fpread to a yard fquare, and its leaves and branch- es grow to a very furprifing fize. The flowers of this fpecies are of no great beauty, but its Ice-like appearance in the midft of fummer is fo lingular, as to make it very univerfally admired.
ICHNEUMON, in zoology, the name of an animal, of which there have been a multitude of idle and fabulous things afferted. It is a creature of the wcafel kind, with a Jonger and narrower body than a cat, and fomething ap-
proaching both in fhape and colour to the badger. Its nofe is black and fharp, like that of a ferret. It has no beard, or whifkers : Its nofe is prominent, and its ears fhort and round. Its colour is a yelfowifh grey, much like that of fome of^the monkey clafs. This is its appearance when in a good humour; but when frighted or provoked, it raifes its hairs upright, and fheWs them variegated at intervals with grev and yellow in diftinct portions. Its legs are fhort, and its feet have all five toes. Its tail Is very long, and thick at the infertion ; its teeth, and its tongue, like thofe of the cat. And what is very fingular, is, that in both fexes it has A large aperture fituated below the anus, which it dilates and contracts at pleafure. Hence came the old opinion, that both male and female conceived, and brought forth young in this animal. It is naturally a very cleanly animal, and is very brifk and nimble, and of great courage. It will en- gage a large dog, and if it have a quarrel with a cat, will deftroy that creature by three bites on the throat. Its nofe is fo fharp and narrow, that it can very hardly lay hold of any thing large with its teeth, and fcarce can bite a man's clenched fift. It is very expert in feizing its prey ; it ftands erect on its hinder legs to defcry where it is, then throwing ltfelf flat on its belly, crawls very flyly towards it, and when within reach, darts violently upon it. It feeds indifferently on all animals that it can get at. Its common food are the fnail, the lizard, the chameleon, fuch ferpents as it can ma- nage, and frogs and mice ; it is alfo very fond of birds, and of none fo much as the hen and chicken. Ray's Syn. Quad, p. 201.
It is much valued in iEgypt for deflxoying ferpents, and is kept tame in the houfes, as the cat with us. The people call it Pharaoh's rat, and the peafants frequently bring its young to market. Bellonius de Animal:
IcHNEt/MON-/"^7/p, the name given by the old writers on in- fects to the fmall flender-bodied wafp, which is frequently found about mud-walls and dry banks of earth: It is very different from the fly limply called the Ichneumon \ of which there are numerous fpecies. This is a true wafp, and is mottled with black and yellow in the manner of the com- mon wafp.
Ichneumon-./^. Thefe flies fometimes are at great pains to deftroy and carry the caterpillars, in whofe bodies they in- tend to lay their eggs, to places where it is proper thofe eggs fhould be hatched. There is one fpecies whofe worm produced from the egg can never fucceed, unlefs it be both bred in the body of a caterpillar, and alfo have that habita- tion bury'd under ground. To this purpofe the parent-fly, when the time of her laying her eggs is come, forms a hole in the ground, which fhe covers with a little clod of earth, that no duff may fall in to fill it up ; when this is prepared fhe goes out in fearch of a caterpillar, proper for her pur- pofe. Dr. Lifter affures us, that he has often feen one of thefe flies feize a caterpillar much larger than herfelf for this intent, and tho' this has been at a conliderable diftance from her hole, fhe has with great labour dragged the creature to it; as foon as fhe arrives with this load fhe takes off the little pellet of earth from the mouth of the hole, and goino- down into it to fee that all is right and ready for the recep- tion of the new gueft, fhe returns out of it and draws in the caterpillar, which fhe leaves there, after giving it fuch wounds as tho' they will not caufe immediate death, yet will difable the creature fo far as to make an efcape impracticable. When the creature is thus lodged, fhe depofits her eggs in its flefh. And this great bufinefs being done, fhe flops up the orifice of the hole very firmly with feveral pellets of dirt, and with duft carefully rammed in between, and will even fly up into gummy and refmous trees to get a cement to hold all firmly together. When the hole is thus filled up, even to the furface of the reft of the ground, fhe draws a leaf or two to the place, and laying them over the mouth, flies away. There is after this no more care taken, but the young worms are hatched from the eggs, and feed on the flefh of the caterpillar till they are full grown. They then change into the nymph ftate, and come out of that in form of their parent flies, in which ftate they eafily make their way out of the ground. Some of thefe Ichneumons make the bodies of other fmaller flies the places of hatching their eggs. They may be often met with flying with one of thefe fmall flies in their legs, the head of it being held clofe to their bellies. If they be watched on this occafion, they will be found ufually to carry thefe flies to certain holes in the ground refembling worm-holes. The firft that they carry ferves as the nidus for their eggs, the reft are for food for their young while in the ftate of worms ; thefe being too voracious to be long fubfifted on the body of one fly, and therefore their parents carry them more every day. The old ones on this occafion crawl backwards into the hole, dragging in the flies after them. When their young worms have fed fufficiently they are converted into nymphse ; the cafes of which are made up of the wings, legs, and other hard parts of the flies they had been feeding on. Phil. Tranf. N° 7 6.
ICHTHYOCOLLA {Cycl.)—Ifmg-glafs, a very valuable glue s to be made of this drug. See the article Glue.
