Page:Cyclopaedia, Chambers - Supplement, Volume 1.djvu/763

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iiiufcles of it extended before the raicrofcope in the fame manner as the skin was, the ftru&ure of thefe mufcles is beautifully feen, they being all made up of bundles of tranfpa- rent firings or fibres, all lying parallel to one another, and are joined by a common membrane.

Thefe firings or fibres appeared alfo thro' their whole length made up of roundifh veficles, and refembled rufhes divided lon- gitudinally ; but there is no certainty of any circulation being feen in thefe.

When this has been fufficiently examined, a part of the crea- ture's gut being pulled out and extended with the mefentery, there is feen the fineft of all views of the circulation of the blood. Words are not able to defcribe this wonderful fcene. The blood is feen pafling through numberlefs vefiels at one and the fame inftant, in feme one way, and in others directly the contrary. Several of the veflels are thus magnified to more than an inch in diameter, and the globules of the blood roll- ing through them appear near as large as pepper-corns ; while in many of the minuteit veflels only fingle globules were able to find their paflage, and that too by changing their fhape in- to an oblong fpheroide. The puliation and acceleration of the blood in the arteries is thus alfo very beautifully feen. As the animal under examination grows languid and near expi- ring, the blood in the arteries will often flop on a fudden, and feein as if it were coagulating, and will then run back for fome time ; after which it will again recover its natural courfe with a great deal of rapidity. A due confideration of thefe particulars may poflibly account for the intermiffions, ftarts and irregularities in the pulfe of perfons near death. Baker's Microfcope, p. 136.

YrqgJiJ/j, in ichthyology, an Englifh name for the rana pifca- trix or lophius. See Rana Pifcatrix.

FRONDES, among botanifts. See Leaf.

FRONT half files, in the military art. See File Leaders.

FRONTATED, in botany, a term ufed to exprefs the leaf of a flower, which grows broader and broader, and ufually ter- minates in a right line. It is ufed in opposition to cufpidated or fpear-pointed, the common term for the petals of flowers which end in a point. Miller's Gard. Di£t. See Leaf.

FRONTIS Os. See Osfrontis.

FROST [Cycl.)'— In very cold countries meat may be preferved by the fro/} for fix or feven months, and prove tolerable good eating. See Captain Middleton's Obfervations made in Hud- fon's Bay, in the Phil. Tranf. N° 465. Se£t. 2. In that climate the fro/} feems never out of the ground, it ha- ving been found hard frozen in the two fummer months. Brandy and fpirits of wine, fet out in the open air, freeze to folid ice in three or four hours. Lakes and ftanding waters, not above ten or twelve feet deep, are frozen to the ground in winter, and all the fifh therein perifh.

But in rivers, where the current of the tide is ftrong, the ice does not reach fo deep, and the fifh are preferved. Springs have never yet been found free from freezing, though lying ever fo deep ; fo that the water ufed is melted fnow and ice. Id. ibid. See Freezing.

Frost, in gardening, husbandry, &c. — Our old authors have given many idle admonitions about preferving the fruit-trees from the injuries of fro/Is, fome of which are religioufly be- lieved and pradlifed by fome to .this day. One is the placing a veflel of water on fome part of the tree, that the fro/} may feize upon that, and fo let the tree efcape. Others ufe a per- nicious method inftead of this idle one, which is the digging a trench about the roots of their trees, and keeping it fupplied with water during the whole feafon of the fpring frofis. This has hurt many good trees.

The great power of fro/} on vegetables is a thing fufficiently known ; but the differences between the frejls of a fevere winter, and thofe which happen in the fpring mornings, in their effects on plants and trees, were never perfectly explain- ed, till by Mefl". Du Hamel and DeBuffon, in the Memoirs of the Paris Academy.

The accurate knowledge of vegetables, which is fo material a part of agriculture, as to deferve the attention of all who wifh well to their country, is however a thing only to be arrived at in length of time, and by a great number of experiments, iuch as no one man's life can give him opportunities of making; and even thofe which have been made feemingly with the greatefi care and caution in one place, and have fcrved for the eirabliihment of rules with one author, have been found to fucceed very differently, and to give very diffe- rent ideas in another place, and to another perfon. The fro/is of fome winters have been fo fevere, as to deflrroy aliiioit all the tender vegetables ; and that fevere one of 1709, gave the world proofs of more than was before fuppofed could be done by them. The corn that was fbwn, and molt other feeds in the ground, periflied entirely. The hazels and fil- bert trees periflied ahr.oft without exception j and many of the more hardy fruit trees periflied to the ground, but fhot out afterwards new branches from the root or flock, while fome of tiie larger trees, which were very vigorous and ftrong, threw out leaves in the fpring on almoft all their branches, and

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fcemed to have differed very little; though in reality they had (uitamed many irreparable injuries, which did not then appear. 1 hefrofts of fevere winters are thus able to injure all the ve- getable world. Thofe of the fpring however are much lefs terrible. Thefe (bmetimes injure the young feedling plants ; but they never are able to arM the folid parts of trees, or hurt their trunks or larger branches, tho' they too often de- stroy their buds, and take off the embryo fruits of the grow- ing year; and are not much lefs detrimental to the foreft than to the fruit trees, as they flop the growth of thofe buds which would grow into branches.

The fro/Is of fevere winters are greatly more terrible than thole of the fprmg, as they bring on a privation of all the produas of the tenderer part of the vegetable world ; but then they are not frequent, fuch winters happening but once perhaps in an age, and the fro/Is of the fpring are in reality greater injuries to us than thefe, as they do us great injuries, though not fo terrible as the others, and 'thefe are every year repeated.

In regard to trees the great difference is this, that the frojls of fevere winters affeft even their wood, their trunks and large branches ; whereas thofe of the fpring are only of power to hurt the buds. Thefe two feafbns of frafls ad in very diffe- rent circumftances, and thofe fituations and expofures where the vegetables have fuffered moft in the winter's/ro/fr, are often found to be leaft affefled by thofe of the fpring. This is a truth that can only be found out by frequent obfervations, which however are not to be regarded as mere matter of fpe- culation, but may have their ufe in the teaching us to guard againft the mifchiefs they warn us of. The winter frojls hap- pening at a time when moft of the trees in our woods and gar- dens have neither leaves, flowers, nor fruits upon them, and have their buds fo hard as to be proof againft flight injuries of weather, efpecially if the preceding fummer has not been too wet ; in this ftate, if there are no unlucky circumftances attending, the generality of trees bear moderate winters very well ; but hard frojls, which happen late in the winter, caufe ' very great injuries even to thofe trees which they do not utter- ly deftroy. Thefe are, i. Long cracks following the direai- on of the fibres. 2. Parcels of dead wood inclofed round with wood yet in a living ftate. And, 3. That diftemperature which the forefters call the double blea, which is a perfeft circle of blea, or foft white wood, which, when the tree is afterwards felled, is found covered by a circle of hard and fo- lid wood. The blea is in its natural ftate an outer circle of white and imperfeft wood unrounding the hard and more per- fea wood of the tree, and furrounded by the bark, and is eafi- ly diftinguifhed in moft fpecies from the hard wood or heart of the tree by its different colour and want of hardnefs. The found or perfefl wood in trees, in their natural ftate, is all of one colour and hardnefs from its.circumference to its center; but in thefe injured trees the blea furrounds the heart, and more of the heart furrounds the blea, which appears again in an outer circle round that, and covered by the bark. This is the ftate of a tree before and after being injured by frtfl ; and in this ftate are trees found on the felling in different degrees, according to the different foils and fituations in which they ftand. In ftrong foils, and in the covert of forefts, where the trees are well rooted, and well ftielter'd and defended, this diftemperature is found lefs frequent, and in lefs degree, than in thofe trees which ftand expofed, and are rooted in a laxer earth. The fole infpeflion of thefe circles of falfe blea, as the inner circle of white wood may very properly be called, ihews them to be very poor and weak ; and experiment abun- dantly proves the truth of the opinion. Beams cut of the fame fize out of the true blea and this falfe blea, by the weights required to break them, fliewed the difference very plainly ; the natural blea bearing twice the weight, or being of double the ftrength of this in its unnatural ftate. Though the blea at beft is of no great ftrength, compared with that of the pel fea wood of the tree.

The fpecific gravity of the true blea is alfo much greater than that of this falfe kind ; but the outer circle of found wood furrounding this falfe blea is found to be of equal weight and hardnefs with the heart or central wood ; fo that whatever perfea wood is found in the tree, appears to be all of the fame quality. Notwithftanding that, there is this great dif- ference between the two bleas, the inner being ever lighter and weaker, even though it have been formed twenty or thirty years before, as may be known by the annual circles which appear on the outlide of it.

The number of obfervations which Mr. Reaumur made of this blea in trees of different parts of France, all {hewed him the falfe blea under the fame number of annual circles of the after-growth of the tree; and thefe being counted, proved juit as many as the number of years fince 1709 ; whence he very juftly concluded, that all the falfe blea he found throughout the kingdom was the eftea of the feverity of this one hard winter. And it is very evident, that this falfe blea is that part of the tree, which in the year 1709 was the true and natural blea, and which the feverity of the frafls of that win- ter prevented from ever becoming the found and folid wood,

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