Monthly Archives: April 2014
350.HOW DOES A STEAM ENGINE WORK?
In trying to build machines that do work for him, man has usually freed, or changed, or channeled the forces that exist in nature. When we boil water we change it into a gas, which we call steam. This gas tries to expand, that is, push aside or ahead whatever is in its way. A steam engine uses this force in steam to do work.
JAMES WATT
349.HOW CAN GLASS BE BLOWN?
When glass is in a melted state, it can be “worked” in many ways. It can be blown, pressed, drawn, or rolled. For hundreds of years, the chief method of working with glass was blowing. The glass-worker gathered a ball of molten glass on the end of his blow-pipe and blew, just the way you would blow a soap bubble. Using his skill, he shaped the glass as he blew, and drew it out to the correct thinness. He kept reheating the glass to keep it workable, and then he would finish it with special tools.
348.HOW ARE MARBLES MADE?
It is a curious thing how boys of all times in all countries seem to get the same idea about games. The game of marbles for instance, which is played in every city in this country, has been played all over the world practically since the beginning of history!
Nobody knows just when marbles began, but it probably goes back to the first time somebody discovered that a round stone pebble would roll. And that goes back at least to the Stone Age. Scientists have discovered among Stone Age remains little balls which were too small to be used for anything but games.
