FROST. 



FRUIT. 



are so hard as to withstand the effects of con- 

 gelation ; but hard frosts late in spring are 

 often very injurious, as the buds are then ap- 

 pearing. Fruits are in like manner destroyed 

 by frost. Their watery portion being changed 

 into crystals of ice, occupying a greater space 

 than the fluid from which they were produced, 

 burst the small vessels in which they are 

 formed ; hence the fruit is deprived of its fla- 

 vour, and when thawed putrefies. 



The hoar-frost or white frost, which appears 

 in the mornings chiefly in autumn and spring, 

 is merely frozen dew. It is generally the con- 

 sequence of a sudden clearing up of the wea- 

 ther after rain, when a considerable degree of 

 cold is produced by the rapid evaporation. In 

 northerly climates, it usually happens that 

 after a fall of rain the wind shifts into a north- 

 ern quarter, and the atmosphere suddenly clears 

 up. When this takes place during the night, or 

 early in the morning, a strong radiation of heat 

 from the earth commences, the cooling effect 

 of which is increased by the copious evapora- 

 tion from the wet surfaces of the plants and 

 the grass. The influence of evaporation on 

 the phenomenon is obvious from this, that the 

 moisture which appears in the form of dew be- 

 fore sunrise, is often changed into rime, or hoar- 

 frost, on the appearance of that luminary. The 

 reason is, that as the atmosphere begins to be 

 warmed by the sun's rays, the evaporation is 

 accelerated, and consequently the cold at the 

 wet surface of the ground augmented ; hence, 

 we see one reason why frosty nights are so 

 much more prejudicial to the tender shoots of 

 plants when they are succeeded by very bright 

 mornings. Hence, also, hoar-frost is found 

 on grass or plants, when the thermometer, 

 placed a few feet above the ground, indicates 

 a temperature three or four degrees above the 

 freezing point. 



In late autumnal frost, the effect of evapora- 

 tion by the heat of the sun is often exemplified 

 on the stems of potatoes. If a hoar-frost be 

 immediately succeeded by the influence of the 

 sun, the dew liquefies, and by the process of 

 evaporation the stalks lose their vitality,- for 

 although plants, as well as animals, have an 

 inherent power of resisting cold, yet it is in the 

 former only to a very limited degree. If the 

 hoar-frost be brushed off (and this can easily 

 be done by two men moving along the beds or 

 drills with a rope between them, very early in 

 the morning, before the evaporation takes 

 place), the stalks will sustain no injury. The 

 destructive power of evaporation appears to 

 be proportioned to the degree of humidity in 

 the body on which it acts. 



The following is recommended as a simple 

 and easy method of securing fruit trees from 

 the effects of frost : 



If a thick rope be intermixed among the 

 branches of a fruit tree in blossom, the end of 

 which is directed downwards so as to terminate 

 in a pail of water, should a slight frost take 

 place during the night, it will not in the small- 

 est degree affect the tree, while the surface of 

 the pail which receives the rope will be cover- 

 ed with thin ice ; though the water placed in 

 another pail by the side of it, by way of expe- 

 riment, may not, from the slightness of the | 

 508 



frost, have any ice on it at all. In this case 

 the rope aids the evaporation of the water, and 

 thereby cools it down to the freezing point. , 

 Frost is merely the effect of cold, which, itself, : 

 is a negative quality ; namely, the absence of 

 heat. As evaporation carries off heat and re- 

 duces temperature, whatever aids this is fa- 

 vourable to freezing. (Quart. Journ. of jQgr. vol. 

 viii. p. 421.) Early hoar-frost may, it is said, ' 

 be rendered harmless in its effects by pouring : 

 fresh spring water on the trees and vines thus 

 covered before the sun rises. Various other 

 projects have been proposed at different times 

 to avert the disastrous effects of the morning 

 frosts on vegetation in spring; but, unfortu- 

 nately, it is only on a very limited scale that 

 any means can be adopted for the purpose. 

 Whatever prevents the formation of dew will 

 protect plants ; hence a covering of net or thin 

 gauze will often preserve the blossoms of wall- 

 fruit. But the most effectual means is to check 

 the radiation, by screening the plant from the , 

 chilling aspect of the clear sky. See DEW. 

 Every farmer knows that frost in winter is 

 serviceable to the soil, by breaking down and 

 pulverizing land, and that a failure of crops 

 frequently takes place after a winter of ex- 

 treme mildness. The principle is this : in the 

 process of congelation, the water, as it freezes, 

 expands, and, therefore, necessarily separates 

 the particles of earth in which it is held: frost 

 thus operates better than any instrument of 

 human construction, for its action reaches to 

 the minutest particles, and thus renders them 

 friable. In dry earth it has little or no effect 

 in this way, but is beneficial in destroying 

 grubs and insects. On sand it makes no im- 

 pression. On ploughed clay-land frost has the 

 most beneficial effect. Therefore, where the 

 soil is close, stiff, or of an obstinate clayey na- 

 ture, it should be turned up in ridges in the 

 autumn or at the beginning of winter, which 

 tends greatly to separate its particles, and ren- 

 der it more fine and mellow. 



Hard winters seldom injure winter grain in 

 any respect, especially where the land has been 

 thoroughly drained, and is covered much with 

 snow. By leaving the earth in a loose and 

 finely divided state, frost adapts it better for the 

 extension of the roots as the warmth of spring 

 approaches, and thereby enables them to pro- 

 duce strong plants. (Brande's Diet, of Science.) 



FRUIT (Fr. fruit ; It. frutta ; Span, fruta; 

 Lat. fructum}. In botany, comprehends many 

 kinds of what are commonly called seeds ; as 

 those of corn, buckwheat, caraway, parsley, 

 &c., as well as the succulent inflorescence of 

 the pine-apple, which is a mass of ovaria and 

 envelopes in a consolidated condition. But 

 horticulture the term fruit is restricted to tl 

 pulpy and juicy seeds of trees and shrubs, &C. 

 as the apple, the peach, the currant, &c. 



The fruits of vegetables are equally various 

 with the seeds. They almost all contain an 

 acid ; and this acid is usually either the tar- 

 taric, the oxalic, the citric, or the malic, or a 

 mixture of two or more of them. Hardly any 

 other, except, perhaps, the acetic, has hitherto 

 been found in fruits. They usually contain 

 likewise a portion of saccharine gummy mat- 

 ter, sometimes starch; and the fleshy fruits 



as 



<T ; 



of 



Hid 



the 

 :c., 



