How wonderful it is to see flame bursting out under water, and rising through it! Pray, how is this accounted for? MRS. B. Cannot you find it out, Caroline? EMILY. Stop--I think I can explain it. Is it not because the sulphuric acid decomposes the salt by combining with the potash, so as to liberate the oxy-muriatic acid gas by which the phosphoric is set on fire? MRS. B. Very well, Emily; and with a little more reflection you would have discovered another concurring circumstance, which is, that an increase of temperature is produced by the mixture of the sulphuric acid and water, which assists in promoting the combustion of the phosphorus. I must, before we part, introduce to your acquaintance the newly-discovered substance IODINE, which you may recollect we placed next to oxygen and chlorine in our table of simple bodies. CAROLINE. Is this also a body capable of maintaining combustion like oxygen and chlorine? MRS. B. It is; and although it does not so generally disengage light and heat from inflammable bodies, as oxygen and chlorine do, yet it is capable of combining with most of them; and sometimes, as in the instance of potassium and phosphorus, the combination is attended with an actual appearance of light and heat. CAROLINE. But what sort of a substance is iodine: what is its form, and colour? MRS. B. It is a very singular body, in many respects. At the ordinary temperature of the atmosphere, it commonly appears in the form of blueish black crystalline scales, such as you see in this tube. CAROLINE. They shine like black lead, and some of the scales have the shape of lozenges. MRS. B. That is actually the form which the crystals of iodine often assume. But if we heat them gently, by holding the tube over the flame of a candle, see what a change takes place in them. CAROLINE. How curious! They seem to melt, and the tube immediately fills with a beautiful violet vapour. But look, Mrs. B., the same scales are now appearing at the other end of the tube. MRS. B. This is in fact a sublimation of iodine, from one part of the tube to another; but with this remarkable peculiarity, that, while in the gaseous state, iodine assumes that bright violet colour, which, as you may already perceive, it loses as the tube cools, and the substance resumes its usual solid form. --It is from the violet colour of the gas that iodine has obtained its name. CAROLINE. But how is this curious substance obtained? MRS. B. It is found in the ley of ashes of sea-weeds, after the soda has been separated by crystallisation; and it is disengaged by means of sulphuric acid, which expels it from the alkaline ley in the form of a violet gas, which may be collected and condensed in the way you have just seen. --This interesting discovery was made in the year 1812, by M. Courtois, a manufacturer of saltpetre at Paris. CAROLINE. And pray, Mrs. B., what is the proof of iodine being a simple body? MRS. B.