F R O'

SOB

FRO

fo! ingO: the leaves or plants. It js also used, by ellipsis, (or thetime of unfolding.

FROMSAC, a town of France, in the department of the Gi-ronde , and late province of Guienne, 22 miles N. E. of Rour-deaiiN.

FRONT, in anatomy, the forehead, or that part of the faceabove the eyebrows. The Latin. /rons, is derived by Martiniu-from die Greek f/pinr, to think, or perceive: of f j>iv, the mind orthought.

Front, in architecture, denotes the principal face or side of abuilding, or that presented to their chief aspect or view.

FRONTAL, in architecture, a little trout on, or pedimentsometimes placed over, a small door, or window.

Frontal, Frontlet, or Brow band, in the Jewish ceremo-nies, consists of lour several pieces of vellum, on each of which iswritten some text of scripture.

FRONTIERS, the extremes of a kingdom or country, whichthe enemies tind n front when they would enter it. They wereanciently called Marches.

FRONTIGNAC, FRONTICNAN, or FRONTIGNIAC,a town of France , in the department of Heratilt, and Jate provinceof Languedoc , famous for its excellent wines. It is 12 milesS. S. W. of Montpelier.

FRONTINAC, Fort, a fortress of Canada , on the N. \V.side of Lake Ontario , three miles from its mouth, and 300 fromQuebec .

FRONTINUS, Sextus Julius, an ancient "Roman author , ofconsular dignity, who flourished under Vespasian, Titus , Domi-tian, Nerva, and Trajan , lie commanded the Roman armies inBritain; was made city-prxtor when Vespasian and Titus wereconsuls; and curator ot the aqueducts by Nerva , which occasion-ed his writing l)e Aqiurductibus Urbis Roma’, lie wrote fourbooks upon tlieGreek and Roman art of war; a tract Dr Re Agra-ria, and another IJe Limitibus. These have been often separatelyprinted ; hut were all collected together in a neat edition at Am-sterdam , in ltibl, with notes by Robert Kenclicn. He died un-der Trajan .

FRONTIS OS, in anatomy, called also os coronals, the boneof the forehead See Anatomy.

FRON 1'lSl’IECK OF A ROOK, an ornament with an en-graved title on the fir -t page, or more properly an emblematicalengraved device fronting the title-page.

FRONZELI.A, one of the 17 almost inaccesssible passesthrough the mountains of Vicenza , in Maritime Austria, com-mencing in the valley of Breala.

FROSE, a town of Upper Saxony, in the duchy of Magde-burg , 10 miles S. of Magdebu; gh.

FROSSAY, a town of France , in the department of LowerLoire, 4' miles S. K. of Pauline uf.

FROST, or FREEZING, in physiology, is such-a state ofthe atmosphere, as occasions tiie congelation or freezing of waterand other fluids. See Freezing. Under the articles Cold,( Congelation, Evaporation, Fluidity, and Freezing, it isshewn, that water and other fluids are capable of containing thedement ot fire or heat in two very different states. In the one,they seem to imbibe lire in such a manner, that it eludes all themethods by which we are accustomed to observe it, either bv oursensation of feeling, or the thermometer ; in the other, it manifestsitself obviously to our senses, either hy the touch, the thermo-meter, or the emission ot light. In the first of these states, we callthe body cold ; and are apt to say that tins coldness is occasionedby the absence of heat. But this mode of expression is not itricllyjust, for even those fluids which are coldest to the touch contain avast deal of heat. 'Thus vapour, which is colder to the touchthan the water from which it was raised, contains an immensequantity of fire. 'The same may he said of common salt, andsnow, or ice. [faquantity of each of these sub-t: nces is separatelyreduced to 2$° or 30° ot bahrenheit’s thermometer, upon mixingthem together, the heat which could have raised the thermometerto the degree above-mentioned, now enters into the substance ofthem in such a manner that the mercury falls down to 0. HereN an excessive degree of cold is produced, and vet we are sure thatthe substances contain the very same quantity of heat that theyformerly did; nay, they will even seem exceedingly cold, whenthey most certainly contain a great deal more heat than they ori-

ginally did; for they absorb it from all bodies around them ; andit a small vessel full of water is put in the middle of such a mix*

1 ure, it will in a short time be full of ice. It appears, therefore,that our senses, even when assisted hy thermometers, can onlyudge ot the state in which the element of fire is with relation totne bodies around us, without regard to the quantity contained in'them. '1 Ims, if heat .'lows from any part oi our body into anysubstance actually m contact w ith it, the sensation of cold is excit-ed, and we call that substance cold ; 1 ut it it flows from any sub-stance into our body, the sensation of heat is excited, and wc callthat subst., 1 *. e hot, without regard to the absolute quantity con-tained in either ease. See Calc» uc. Of all known substances,the atmosphere either ab cirbs or throws out heat with the most re-markable facility : and in one or other of these states it always iswith respect to the surface of the earth, and such bodies as areplaced on or near it; tor these, properly speaking, have no tem-perature of their own, but are entirely regulated by that of die at-mosphere. When the air has been tor some time absorbing theheat from terrestrial bodies, a frost must be the undoubted conse-quence, lor the same reason that water freezes in a vessel put intoa freezing mixture: and were this absorption to continue foralength of time, the whole earth would be converted into a frozenmass. There are, however, certain powers in nature, by whichthis effect is always prevented ; and the most violent frost we canimagine must always, as it were, defeat its own purposes, and endin a thaw. 'To understand this subject, we must observe, 1. Inthat state of the atmosphere which w e denominate frost, there is amost intimate union between the air and the water it contains ; andtherefore frosty weather, except in very high latitudes, is generallyclear. 2. When such an union takes place, either in winter ormilliner, we observe the atmosphere also inclined to absorb heat,and consequently to grow fro-ty. Thus in clear settled weather;even in summer, though the dav he excessively hot by the con-tinued sunshine, yet the mornings and evenings are remarkablycold, and sometimes even disagreeably so. 3. ’The air beingtherefore always ready in the time of frost or in clear weather, toabsorb heat from every sulMatice which comes into contact with it,it follows that it must also absorb part of that w liich belongs to'tbevapours contained in it. 4. 'Though vapour is capable of becom-ing much colder than water wihout being froz> j ii, yet by a con-tinued absorption it must at last part with its latent heat, i. c. thatwhich essentially constitutes it vapour; and without which it is n<>longer vapour, but water or ice. No sooner, therefore, does thefrost arrive at a certain pitch, than the vapours, everywhere diS'persed through tin; air, give out their latent heat: the atmospherethen becomes clouded : the frost either goes olf, or become*milder, by the great quantity ot heat discharged into the air; andthe vapours descend in rain, hail, or snow, according to the partfcular disposition of the atmosphere at the time. 3. Even in thepolar regions, where it may be thought that the frost must increasebeyond measure, tin rc are natural means for preventing its run-ning to extremes. 'I he principal cause here is, the mixture ot agreat quantity of vapours from the temperate regions of the glob 1 ’with the air in those dreary climates. R is well known, dialaqueous vapour always Hies from a warm to a colder place. ' l'° rthis reason, the vapours raised hy the sun in the more temperateregions of the earth, must continually lly northward and south'ward in great quantities. Thus tliev furnish materials for tlios eimmense quantities of snow and ic e w hich are to be found in theneighbourhood of the poles, and which we cannot imagined 11 ’

weak influence of the sun in these parts capable of raising.

It i*

nr.posvble that a quantity ol vapour can be mixed with frosty albwithout communicating a great deal of heat to it; and thus thcicare often thaws of considerable duration even in tliose clitnaR*where, from the little influence of the sun, we should supposed 1 ®frost would be perpetual. 0. We may now account with soil'*-probability for the uncertain duration of frosts. In Britain the)are seldom of a long continuance ; became the vapours raise. 1from the sea with which our island is surrounded, perpetually i'd*with the air over it, end prevent a long duration of the frost. ^°.the same rca-on, frosts are never ol such long duration in u' arltime places on the continent as in the inland ones. 'There > sthing, however, more uncertain than the motion of the vapo" r _with which the air is constantly filled : and therefore it is imp 0 *,siblc to prognosticate the duration of a frost w ith any degree e

certaiiHJ.