General Science

318. The Dynamo. We have learned that cells furnish current as a result of chemical action, and that the substance usually consumed within the cell is zinc. Just as coal within...

149. Labor-saving Devices. To primitive man belonged more especially the arduous tasks of the out-of-door life: the clearing of paths through the wilderness; the hauling of mate...

249. The Senses. All the information which we possess of the world around us comes to us through the use of the senses of sight, hearing, taste, touch, and smell. Of the five se...

The plain cotton frock of our grandmothers had its death knell sounded a few years ago, when John Mercer showed that cotton fabrics soaked in caustic soda assumed under certain...

35. Why Things Burn. The heat of our bodies comes from the food we eat; the heat for cooking and for warming our houses comes from coal. The production of heat through the burni...

181. "As difficult as for water to run up a hill!" Is there any one who has not heard this saying? And yet most of us accept as a matter of course the stream which gushes from o...

I. Value of Fire. Every day, uncontrolled fire wipes out human lives and destroys vast amounts of property; every day, fire, controlled and regulated in stove and furnace, cooks...

20. Boiling. _Heat absorbed in Boiling_. If a kettle of water is placed above a flame, the temperature of the water gradually increases, and soon small bubbles form at the botto...

107. Bent Rays of Light. A straw in a glass of lemonade seems to be broken at the surface of the liquid, the handle of a teaspoon in a cup of water appears broken, and objects s...

193. It is by no means unusual for the residents of a large city or town to receive through the newspapers a notification that the city water supply is running low and that econ...

_Third._ The percussion instruments, in which sound is produced by the motion of stretched membranes, as in the drum, or by the motion of metal disks, as in the tambourines and...

75. The Instability of the Air. We are usually not conscious of the air around us, but sometimes we realize that the air is heavy, while at other times we feel the bracing effec...

55. The Body as a Machine. Wholesome food and fresh air are necessary for a healthy body. Many housewives, through ignorance, supply to their hard-working husbands and their gro...

98. What Light Does for Us. Heat keeps us warm, cooks our food, drives our engines, and in a thousand ways makes life comfortable and pleasant, but what should we do without lig...

171. Small boys soon learn the power of running water; swimming or rowing downstream is easy, while swimming or rowing against the current is difficult, and the swifter the wate...

65. Destructive Action of Water. The action of water in stream and sea, in springs and wells, is evident to all; but the activity of ground water--that is, rain water which sink...

304. In the twelfth century, there was introduced into Europe from China a simple instrument which changed journeying on the sea from uncertain wandering to a definite, safe voy...

120. The Magic of the Sun. Ribbons and dresses washed and hung in the sun fade; when washed and hung in the shade, they are not so apt to lose their color. Clothes are laid away...

296. An Electric Current acts like a Magnet. In order to understand the action of the electric bell, we must consider a third effect which an electric current can cause. Connect...

126. The Rainbow. One of the most beautiful and well-known phenomena in nature is the rainbow, and from time immemorial it has been considered Jehovah's signal to mankind that t...

85. Bicycle Tires. We know very well that we cannot put more than a certain amount of water in a tube, but we know equally well that the amount of air which can be pumped into a...

141. We seldom consider what life would be without our wonderful methods of illumination which turn night into day, and prolong the hours of work and pleasure. Yet it was not un...

217. The beauty and the commercial value of uncolored fabrics depend upon the purity and perfection of their whiteness; a man's white collar and a woman's white waist must be pu...

312. Danger of an Oversupply of Current. If a small toy motor is connected with one cell, it rotates slowly; if connected with two cells, it rotates more rapidly, and in general...

224. Dyes. One of the most important and lucrative industrial processes of the world to-day is that of staining and dyeing. Whether we consider the innumerable shades of leather...

136. Most bodies which glow and give out light are hot; the stove which glows with a warm red is hot and fiery; smoldering wood is black and lifeless; glowing coals are far hott...

236. Stimulants and Narcotics. Man has learned not only the action of substances upon each other, such as bleaching solution upon coloring matter, washing soda upon grease, acid...

288. Heat. Any one who handles electric wires knows that they are more or less heated by the currents which flow through them. If three cells are arranged as in Figure 200 and t...

280. Many animals possess the five senses, but only man possesses constructive, creative power, and is able to build on the information gained through the senses. It is the cons...

275. Speech. The human voice is the most perfect of musical instruments. Within the throat, two elastic bands are attached to the windpipe at the place commonly called Adam's ap...

213. While baking powder is universally used for biscuits and cake, it is seldom, if ever, used for bread, because it does not furnish sufficient gas to lighten the tough heavy...

244. Nitrogen. A substance which plays an important part in animal and plant life is nitrogen. Soil and the fertilizers which enrich it, the plants which grow on it, and the ani...

14. Temperature not a Measure of the Amount of Heat Present. If two similar basins containing unequal quantities of water are placed in the sunshine on a summer day, the smaller...

231. The prevention of disease epidemics is one of the most striking achievements of modern science. Food, clothing, furniture, and other objects contaminated in any way by dise...

94. Very Small Objects. We saw in Section 84 that gases have a tendency to expand, but that they can be compressed by the application of force. This observation has led scientis...