Now, to give an opinion about the change of hair, we must know something of its nature, and what colors it. Wise men say that light hair is owing to an abundance of sulphur in the system, and dark hair to an excess of iron. So if we comb light or red locks with lead combs for a long time, the lead acts on the sulphureted hydrogen evolved by the hair, and darkens it. If we can neutralize the iron in any way, a contrary effect will be obtained. To do this, work at the dark hair precisely as if it were an ink-spot to be taken out. The skin should not suffer, and to prevent this, oil it carefully along the parting, edges, and crown of the head, wiping the oil from the hair with a soft cloth. Oxalic acid, strong and hot, is the best thing to take out spots of ink made with iron, and we may try this with the hair. To apply this, or any of the preparations named, one should be in undress, wearing not a single article whose destruction would be of account, for all the acids and bleaching powders used ruin clothes if a drop touch them, taking the color out, and eating holes in the stoutest fabrics. The eyelids and brows should be well oiled to prevent the acid from attacking them, and the hands, shoulders, and face will be the better for similar protection. On one ounce of pure, strong oxalic acid pour one pint of boiling water, and, as soon as the hands can bear it, wet the head with a sponge, not sapping it, but moistening thoroughly. The effect may be hastened by holding the head in strong sunlight, or over a register, or the steam of boiling water. Five minutes ought to show a decided change, but if it do not, wet again and again, allowing the acid to remain as long as it does not eat the skin. This may not be hard to bear, but it will make the hair fall out.