To Wash Dust Cloths, Mops, and Floor Cloths. Make a strong soapsuds, or sal-soda solution ; put in the cloths, and poke them around with a stick for five minutes. Lift them out ; pour off the water ; make another suds, and continue this until no more loose dirt comes out into the water. Do not put the hands into the water, until it is nearly clear; then soap well and let the cloths soak until ready to rub them clean. Rinse, shake, and dry quickly. After once trying this method you will see how useless it is to soak cloths in dirty water; the cloth only absorbs the dirt again, and is harder to make clean. CHAPTER VIII HEAT AND FUEL Section I Heat Artificial heat for household purposes is obtained by rapid combustion, or the chemical union of the oxygen in the air with the carbon and hydrogen found in fuel. Hydrogen is a gas, and is the lightest substance known. It is seldom found free in nature, but its compounds are everywhere. Combined with oxygen it forms water and in this form it is found in all animal and vegetable substances. Pure hydrogen burns instantly in the air when lighted and produces intense heat, and the result of the burning is water- vapor. The principal fuels used in household heating are wood, charcoal, anthracite and bituminous coals, kerosene oil, and gas, all composed of either carbon, or compounds of carbon with hydrogen, forming hydro-carbons. Sometimes they contain both. All these varieties of fuel were originally derived from vegetable matter. The living tree or plant, through its leaves and roots, takes in from the air and soil carbon dioxide and water, with earthy and nitrogenous matter dissolved in the water. It gives back to the air a large part of the oxygen contained in the gas, but retains some of it, and especially retains much of the carbon and water. Upon these it lives, and from these, with the help of the sunlight, it constructs the woody fibre, sap, and other sub- stances, — compounds which are rich in carbon. Since 35 36 SCHOOL KITCHEN TEXTBOOK these compounds have been built up by the energy of the sunhght, and can unite with oxygen, they are readily combus- tible. When we burn them in the form of wood, oil, fat, etc., this energy is liberated, or set free, as heat, or light, or both. By heat, which represents a certain amount of energy, we are enabled to have work done : on a large scale, when we burn coal under an engine, and on a small scale when we burn it in our stoves, and use the heat to cook our food. Artificial heat may thus be traced to the sunlight, the chief source, also, of all natural heat. Section II Fuel Wood is a product of vegetable growth, found in the trunks and branches of trees. It contains hydro-carbons in a solid form and consists of slender fibres or tubes closely packed together. When first formed these are hollow, and contain the sap or vegetable juices ; but gradually they become hardened and consolidated, and by their successive layers or rings indicate the age of the tree. Some of the hard woods are oak, hickory, and maple ; soft woods are pine, spruce, and cedar.

AI-modernized reading of the original text

To Wash Dust Cloths, Mops, and Floor Cloths. Make a strong soapsuds, or sal-soda solution ; put in the cloths, and poke them around with a stick for five minutes. Lift them out ; pour off the water ; make another suds, and continue this until no more loose dirt comes out into the water. Do not put the hands into the water, until it is nearly clear; then soap well and let the cloths soak until ready to rub them clean. Rinse, shake, and dry quickly. After once trying this method you will see how useless it is to soak cloths in dirty water; the cloth only absorbs the dirt again, and is harder to make clean. CHAPTER VIII HEAT AND FUEL Section I Heat Artificial heat for household purposes is obtained by rapid combustion, or the chemical union of the oxygen in the air with the carbon and hydrogen found in fuel. Hydrogen is a gas, and is the lightest substance known. It is seldom found free in nature, but its compounds are everywhere. Combined with oxygen it forms water and in this form it is found in all animal and vegetable substances. Pure hydrogen burns instantly in the air when lighted and produces intense heat, and the result of the burning is watervapor. The principal fuels used in household heating are wood, charcoal, anthracite and bituminous coals, kerosene oil, and gas, all composed of either carbon, or compounds of carbon with hydrogen, forming hydro-carbons. Sometimes they contain both. All these varieties of fuel were originally derived from vegetable matter. The living tree or plant, through its leaves and roots, takes in from the air and soil carbon dioxide and water, with earthy and nitrogenous matter dissolved in the water. It gives back to the air a large part of the oxygen contained in the gas, but retains some of it, and especially retains much of the carbon and water. Upon these it lives, and from these, with the help of the sunlight, it constructs the woody fibre, sap, and other substances, — compounds which are rich in carbon. Since these compounds have been built up by the energy of the sunhght, and can unite with oxygen, they are readily combustible. When we burn them in the form of wood, oil, fat, etc., this energy is liberated, or set free, as heat, or light, or both. By heat, which represents a certain amount of energy, we are enabled to have work done : on a large scale, when we burn coal under an engine, and on a small scale when we burn it in our stoves, and use the heat to cook our food. Artificial heat may thus be traced to the sunlight, the chief source, also, of all natural heat. Section II Fuel Wood is a product of vegetable growth, found in the trunks and branches of trees. It contains hydro-carbons in a solid form and consists of slender fibres or tubes closely packed together. When first formed these are hollow, and contain the sap or vegetable juices ; but gradually they become hardened and consolidated, and by their successive layers or rings indicate the age of the tree. Some of the hard woods are oak, hickory, and maple ; soft woods are pine, spruce, and cedar.

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