Other Machines Follow.
The completion of the reaper set the wheels of farm invention spinning. It was the first great battle successfully won and gave a spirit of confidence and an irresistible spirit of victory to the men who were lifting the burdens off the bodies of men. After the reaper, the mowing machine came naturally. Following the binder in easy sequences came the corn binder, push binder, header and harvester thresher.
Every variety of haying machine, from side-delivery rake and tedder to sweep rake and loader, came eventually to make hay-making easy. The thresher, ensilage cutter, riding plow, disk harrow, cream separator, manure spreader and seeding machines succeeded in making the raising of the world’s food a profitable occupation; at the same time, they made it an easy one. Lately, the internal combustion engine, together with its application in the kerosene tractor, promises to make the farmer’s emancipation practically complete. If Herbert Casson could say “The United States owes more to the reaper than it does to the factory or the railroad or the Wall Street stock exchange,” what can be said of these myriad machines that now do the food-grower’s work for him?
Where formerly nearly all the people had to engage in food raising and even then went to bed hungry, now nearly half the people live away from the farm and there is a great abundance of bread and of food.
What Causes an Echo?
An echo is caused by the reflection of sound waves at some moderately even surface, such as the wall of a building. The waves of sound on meeting the surface are turned back in their course, according to the same laws that hold for reflection of light. In order that the echo may return to the place from which the sound proceeds, the reflection must be direct, and not at an angle to the line of transmission, otherwise the echo may be heard by others, but not by the transmitter of the sound. This may be effected either by a reflecting surface at right angles to the line of transmission or by several reflecting surfaces, which end in bringing the sound back to the point of issue.
Sound travels about 1,125 feet in a second; consequently, an observer standing at half that distance from the reflecting object would hear the echo a second later than the sound. Such an echo would repeat as many words and syllables as could be heard in a second. As the distance decreases the echo repeats fewer syllables till it becomes monosyllabic.
The most practiced ear cannot distinguish in a second more than from nine to twelve successive sounds, so that a distance of not less than sixty feet is needed to enable a common ear to distinguish between the echo and the original sounds. At a near distance the echo only clouds the original sounds. This often interferes with the hearing in churches and other large buildings. Woods, rocks and mountains produce natural echoes in every variety, for which particular localities have become famous.
In Greek mythology, Echo was a nymph (one of the Oreads) who fell in love with Narcissus, and because he did not reciprocate her affection she pined away until nothing was left but her voice.