_10th._--The frost was so great last night, that it caused sad mischief. The thermometer sunk to 24°. Mary had two nice hyacinths in bottles; unfortunately, she placed them yesterday in a window where there was a bright sunshine; Frederick having promised to put them back safely in the latter part of the day. He forgot them; but, as soon as he woke this morning, he went to repair his error--when, to his great dismay, he found the glasses burst, and the water lumps of ice.
He went to Mary, but he was so sorry for his negligence, that she could not reproach him. The only thing to be done, she said, is now to consider how to relieve the bulbs from the ice that surrounds them. Frederick proposed placing them near the fire, that the heat might thaw the ice; but Mary told him that she was afraid the sudden change from cold to heat would make the bulbs decay--and that the best plan, she thought, was to put them into cold water. Mary had called me to look at the glasses on the first discovery of the misfortune; and we carried them and the bulbs inclosed in ice, to my uncle, who had just come down to the library, to consult him on what was best to be done. He approved of Mary’s proposal, and said, “That is a practical instance of the advantage of acquiring different kinds of knowledge.” Mary had concluded, that the sudden change of temperature would produce immediate decay in the roots--on the same principle that heat applied to people who have been frost bitten, causes mortification in the frozen part. My uncle afterwards told me, that the same thing happens to the frozen buds of tender plants, which are exposed to the rays of a hot sun before the frost has been dispersed; while those which are gradually thawed receive no injury.
I reminded him of his having spoken of _crystals_ of ice, and asked how that term could be applied to any thing but mineral bodies.
“The term crystal,” he replied, “came from the Greek word for ice--it was afterwards applied to rock crystal, which the ancients imagined to be water converted into stone; but it now signifies the regular figure in which the particles of any substance arrange themselves in passing from the liquid to the solid state.--Each of those substances has a figure for its crystal peculiar to itself, and from which it never varies. Common salt, for instance, dissolved in water, and slowly evaporated, always forms regular _cubic_ crystals of about an eighth of an inch in diameter, and quite transparent; sugar candy is nothing but sugar crystallized into _six_-sided prisms; and alum forms itself into beautiful crystals of _eight_ sides. All this you may easily ascertain for yourself by experiment; and when I have an opportunity of taking you to a smelting house, you will see that in the cooling of melted metals, each metal assumes a crystalline shape belonging to itself.”