Grease removed from Paper.—To remove grease spots from paper, gently warm the greasy part and press it, under and over, with blotting-paper. Repeatedly change the blotting-paper until most of the grease has disappeared. Then heat a very little oil of turpentine until nearly boiling, again warm the paper, and apply the turpentine to the grease spot by means of a camel’s hair brush, on both sides of the paper. Repeat this process until the grease has quite disappeared. Finally, with a clean brush, dipped in spirits of wine, again brush over the spot, and as the spirit evaporates the paper will be left free from grease or stain. Remember that oil of turpentine is very inflammable. It would be safer to heat it in the oven.
Invisible Ink.—Take an ounce of oil of vitriol, and mix with a pint of rain water, and when cool write with a clean pen. When it is cold it will disappear. Heat it and it will appear in black ink. Here are some other inks which appear and disappear at the writer’s will:—
Solution of nitro-muriate of cobalt, when heated turns green; solution of acetate of cobalt, with a little nitre becomes rose-colour when warm. Inks which remain visible when heated, but do not disappear when cooled include, onion-juice, yellow; equal parts of copper and sal-ammoniac in water, yellow; aquafortis, spirits of salt, oil of vitriol, and salt and water, yellow or brown. Inks which appear when exposed to light may be made with diluted solution of nitrate of silver, or with diluted solution of terchloride of gold.
How Leaves Keep Clean.—While leaf shapes have formed a subject of study ever since botanical science has existed, it is only recently that one of the most remarkable purposes which the points of leaves serve has been clearly brought out.
It has been shown, as the result of some special investigations made in Germany, that the long points quickly drain off the excess of moisture deposited upon the foliage in heavy rains.
This ready method of disposing of a surplus of moisture is important to some plants. It also serves as a means of cleaning the surface of the leaves.
Round leaves do not so easily get rid of the rain water, and it has been noticed that they remain dusty and dirty after a shower, the escape of the water by evaporation not tending to cleanse them, while long, narrow, pointed leaves are washed clean and bright.
Deaf and Dumb Alphabet