Frost
The presence of Frost denotes a fall of temperature to a point at which still water becomes solidified; and its intensity is known by the contraction of another liquid used in the construction of the thermometer, which does not become frozen at any temperature experienced in this country. Fahrenheit's scale is that in use for thermometers in Great Britain, and this places freezing point at 32deg., and boiling water at 212deg., the intervening space being divided equally into 180 parts, termed degrees. Similar divisions are made below freezing point, and the fall of the liquid in use, which is either Mercury or Spirits of Wine, below this indicates, in so many degrees, the amount of Frost. On plants or other subjects unprotected, the action of Frost is from the top downwards towards the earth; hence the value of, and safety frequently effected by, slight coverings that are non-conductors of heat, and consequently prevent its loss by radiation. The effect of Frost on plant life is not always in proportion to its intensity or the hardiness of the plant under what may be termed natural conditions. A spell of mild weather frequently places vegetation in a growing and tender state, especially in spring, when a sudden change to a few degrees of Frost may cause more destruction than a great deal at another time, when vegetation was more dormant. Frost acts most injuriously on anything wet, and is least destructive under the reverse condition. It is most successfully removed from plants too tender to withstand it, by adopting a method as gradual in effect as possible. Frost penetrates in a slow and natural way, and the greatest injury, if any, is caused when it is suddenly displaced by heat, either from sunshine or artificially. Syringing is sometimes recommended with tender subjects that have become frozen, but it should be remembered that water which is itself much above the freezing point, will, when applied, cause a sudden change to anything that is considerably below. Frost has a most beneficial effect on all soils exposed to its influence, by penetrating and pulverizing them, so that what was before unworkable and useless, is afterwards rendered fertile and amenable to the successful cultivation of various crops.