« AnteriorContinuar »
tries, and seas; they have learned what others know, of all the countries and oceans in the world; they have drawn maps showing the places of the different countries, the rivers, the towns, the mountains, and the lakes. An account of the earth, is Geography.
The history of thunder, fire, air, water, and light, is called Natural Philosophy.
The noise of thunder, and the bright light which is seen when it thunders, is caused by Electricity.
Dr. Franklin found out electricity. Fire is in every thing with which we are acquainted, even in ice. Things which cause the feeling of heat have a great deal of fire in them; things which cause the feeling of cold, have a smaller quantity of fire in them. Fire gives light, if there is enough of it; another substance, called phosphorus, gives light. Perhaps children have seen old pieces of decayed wood which gave light; that light is given by phosphorus.
Light shows us the things which are about us, and gives them colour. Those things which can be seen, are visible; those which cannot be seen, are invisible. Men and houses are visible —air is invisible. Sight is vision. The light which we see, comes from the sun, or from fires artificially produced. If the light comes straight to our eyes, it is direct-the light from the candle is direct.
If the light comes through any substance, it is refracted the light which comes through the glass window, is refracted, or broken, because it is divided-part of the light is on the outside
of the window, and part on the inside-the window breaks, or divides the light.
The light which falls upon a substance, and does not go through it, is turned back, or reflected. When the candle is held to one side of the looking glass, the light cannot be seen on the other; the quicksilver on one side of the glass, prevents the light from going through it-the light is reflected.
The history of light and vision, is called optics. The organ of sight is the eye. The anatomy of the eye is very curious. The little spot in the middle of the eye is the pupil; the coloured circle which surrounds the pupil, is the iris.
SUBSTANCES which have a sour taste, are acids. Some substances, added to acids, take the sour taste from them; these are Alkalies. When cream is sour, put a little pearl ash into it, and it is no longer sour. Pearl ash is an
Pearl ash is made from the ashes of burnt wood. The ashes are covered with water; the water soon becomes of the colour of coffee, it strained off, and is called ley.
This ley is boiled till it evaporates; at the bottom of the vessel in which the ley is boiled, are found the crystals of pot ash; from the pot ash is made the fine and white Alkali, called pearl ash.
BREAD is made of flour, water, yeast, and a little salt; when these substances are first mixed, the dough takes up a small space; in a short time it begins to swell, or rise, and in a few hours it is fit to bake. Flour and water without yeast, is paste.
The motion and swelling caused by yeast, is fermentation.
Yeast is mixed with hops, malt, and water, to make beer. What is called the working of beer, is fermentation.
Fermentation-the motion and expansion of certain substances, produced by the mixture of them.
Look at the shoes on your feet. They are made of leather. Leather is the skin of dead animals, with the hair taken off. There are two parts to your shoe, and two kinds of leather in it. The upper leather which covers the top of your foot, is of one kind, and the sole or bottom of the shoe is another. The upper leather of shoes is made of calf skin, or sheep skin, or seal skin.
The sole leather is made of the skin of the cow, or ox. After the butcher has killed the animal, he strips off the skin, and sends it to the currier. The currier puts some lime upon it, which loosens the hair; afterwards he lays the skin on a log, and scrapes it quite clean; then
he washes it, and dries it; when it is dry, he colours, or makes it black; and then it is fit for the shoemaker. The thick leather of which the sole is made, is the skin of the ox or cow. When the hair is taken off, the skin is tanned. Tanning is the trade of the tanner. Tanning is done with the bark of a tree, ground fine. The skin is put into water, and this ground bark is spread over it; the leather is left in the bark and water, till it grows stiff and thick.
Almost all children have put alum into their mouths; they know that the alum draws the skin of the mouth, and makes it feel stiff-just so, the bark draws the skin, or sole leather.
This property of some substances to draw up the parts of other things, and make them harder and thicker, is astringency. Alum is astringent, and oak bark is astringent.
The tanned leather is used for the soles of shoes, and some other purposes.
The currier, the tanner, and the shoemaker, are all obliged to labour for us, before we can have shoes.
EAR RINGS are made of gold. Thimbles and spoons of silver. Cents are made of copper. The horses' shoes are made of iron. The spout is made of lead. Candlesticks, pans, and water
ing-pots are made of tin. The back of the looking glass is covered with quicksilver. These are all metals. Metals come out of
People dig into the earth to find metals. The place where metals can be found, is called a Mine. The metal is found in the mine, mixed with dirt, stones, and some other substances; when the metal is found, mixed in this manner, it is called an ore.
Gold is the heaviest of all metals; it weighs more than nineteen times as much as water weighs. That is, a cup full of gold would be more heavy than nineteen cups filled with water.
Silver is eleven times heavier than water.
Iron is eight times heavier than water.
Steel, of which scissors, knives, and many other things are made, is prepared from ironjust such black iron as the stove-it is made so smooth, bright, and sharp, by a particular manner of working it.
Brass, of which knockers, bell handles, little thimbles, and a great many other things, are made, is itself made of copper, and another whitish substance, called zinc. The copper and zinc are melted together, and become brass.
Children often melt lead, and pour it into different shapes. If the melting lead is kept for