"The fragrant lime," said Miss Harson, "has a relative in Asia whose acquaintance I wish you to make, and you know it already in one of its products, which is common in every household. It is also very fragrant--or rather, I should say, it has a strong aromatic odor which is very reviving in cases of faintness or illness, although it has quite a contrary effect on insects, particularly on mosquitoes. I should like to have some one tell me what this white, powerful substance is."