We may now proceed to the alkaline earths, I shall say but a few words on BARYTES, as it is hardly ever used, except in chemical laboratories. It is remarkable for its great weight, and its strong alkaline properties, such as destroying animal substances, turning green some blue vegetable colours, and showing a powerful attraction for acids; this last property it possesses to such a degree, particularly with regard to the sulphuric acid, that it will always detect its presence in any substance or combination whatever, by immediately uniting with it, and forming a sulphat of barytes. This renders it a very valuable chemical test. It is found pretty abundantly in nature in the state of carbonat, from which the pure earth can be easily separated. The next earth we have to consider is LIME. This is a substance of too great and general importance to be passed over so slightly as the last. Lime is strongly alkaline. In nature it is not met with in its simple state, as its affinity for water and carbonic acid is so great, that it is always found combined with these substances, with which it forms the common lime-stone; but it is separated in the kiln from these ingredients, which are volatilised whenever a sufficient degree of heat is applied. EMILY. Pure lime, then, is nothing but lime-stone, which has been deprived, in the kiln, of its water and carbonic acid? MRS. B. Precisely: in this state it is called _quick-lime_, and it is so caustic, that it is capable of decomposing the dead bodies of animals very rapidly, without their undergoing the process of putrefaction. --I have here some quick lime, which is kept carefully corked up in a bottle to prevent the access of air; for were it at all exposed to the atmosphere, it would absorb both moisture and carbonic acid gas from it, and be soon slaked. Here is also some lime-stone--we shall pour a little water on each, and observe the effects that result from it. CAROLINE. How the quick-lime hisses! It is become excessively hot! --It swells, and now it bursts and crumbles to powder, while the water appears to produce no kind of alteration on the lime-stone. MRS. B. Because the lime-stone is already saturated with water, whilst the quick-lime, which has been deprived of it in the kiln, combines with it with very great avidity, and produces this prodigious disengagement of heat, the cause of which I formerly explained to you; do you recollect it? EMILY. Yes; you said that the heat did not proceed from the lime, but from the water which was _solidified_, and thus parted with its heat of liquidity. MRS. B. Very well. If we continue to add successive quantities of water to the lime after being slaked and crumbled as you see, it will then gradually be diffused in the water, till it will at length be dissolved in it, and entirely disappear; but for this purpose it requires no less than 700 times its weight of water. This solution is called _lime-water_. CAROLINE.