Part 75

Now examine closely and you will see that just one-half of the orange is lighted at one time and the other half is dark. You revolve the orange in front of the light slowly and a portion of the surface of the orange is always coming into the light, while a corresponding portion of it on the opposite side is constantly going into the dark. In other words, whatever the speed at which you revolve the orange toward the light, one-half of it is always light and the other half is always dark.

This is exactly what happens in the relation of the earth to the sun every day. One-half of the earth, which is continually revolving on its axis, is facing the sun, and is, therefore, in the daylight, while the other half of the earth’s surface is in darkness, because the light from the sun does not strike any portion of it. If the earth did not revolve one-half of it would always be in day-time, while the other half would be continually having night-time. As the earth is always moving or revolving the half where it is day-time is constantly changing, so that the day is beginning on one-half of the earth’s surface every second of the day. Actually, of course, then, if you live on the east side of town day begins with you a little sooner than with your chum who lives on the west side of town. We have come to measure the beginning of day as sunrise and the beginning of night as sunset, wherever we happen to be.

For convenience in setting clocks and in measuring time we do not take into consideration these very slight differences in the rising and setting of the sun, but set our clocks all alike in different parts of the same town or city to avoid confusion. In fact, in order to overcome the difficulties and confusions arising in reckoning the time of the clock in different localities, and still keep the beginning of what we call day-time constant with the hands of the clock, we have agreed upon what we call standard time. We agreed upon this system of fixing standard time because the actual sun time by which people set their clocks up to a few years ago led to so many mistakes in catching trains, keeping engagements and other misunderstandings where the question of time was involved. Then when this system of standard time was adopted the confusion became even worse, and the mistakes and misses more numerous, because some people insisted on setting their clocks to standard time and others insisted on sticking to the old sun time schedule. So you could never tell by looking at the clock what time it really was unless they put a sign on the clock saying what kind of time they were going by. Finally, however, most of the people came to appreciate that it would be a good idea to use one uniform system of setting the clocks and of having them in harmony in a sense with the other clocks in the world, and the adoption of the standard time plan became universal. To make this system practical and effective, certain points about equally distant from each other were selected, at which point

Where Is the Hour Changed?

the hour would change for all points within that zone. Under this system all timepieces in any one zone point to the same hour. So the clock time changes only as you go east or west. All points on a north and south line have the same time as the zone in which it is located.

For convenience in adjusting the time in America the country was divided into four east and west zones. The first zone takes in everything on a straight north and south line east of Pittsburg, and is called Eastern time. The second zone extends from Pittsburg to Chicago, and is called Central time; the third zone extends from Chicago to Denver, and is called Mountain time; while the fourth zone extends from Denver to the Pacific Ocean. These selections were made because the sun actually rises about one hour later in Pittsburg than in New York; one hour later in Chicago than in Pittsburg; one hour later in Denver than in Chicago, and one hour later on the Pacific Coast than in Denver. Under this plan when it is nine o’clock in New York it is only eight o’clock at Pittsburg and all points in the Central zone; seven o’clock in all points in the Mountain zone; six o’clock in Denver and five o’clock in San Francisco. As you keep travelling westward you drop one hour of the clock time in every zone, and as under this system the earth’s east to west distance is divided into twenty-four such zones, if you went west entirely around the world you would lose a whole day of clock time.

If, however, you went around the world from west to east in the same manner you would gain a whole day.

Where Does the Day Change?

This system of agreeing on fixed places where the hour changes made it necessary to also fix a point where for the purposes of the calendar the day also changes. This imaginary north and south line is fixed upon at 180 degrees west longitude, which would cut the Pacific Ocean in two. This line makes it possible for a person to travel all day before approaching this line and then find himself after crossing it travelling all the next day with the same name for the day of the week. Thus he could spend all of Sunday travelling toward the International Day Line, as this is called, and after crossing it spend another Sunday, which would be the next day, going away from it. This would give him the novel experience of having two Sundays on successive days. The same thing would happen if he were travelling to the Day Line on Monday, Tuesday, Wednesday, Thursday, Friday or Saturday. He would live through two succeeding days of the same name in the same week, one right after the other. This would be in going westward.

If you were traveling eastward and crossed the International Day Line on Sunday at midnight you would lose a day completely out of the week, for when you woke up the next morning it would be Tuesday.

Why Do We Cook the Things We Eat?

We have several reasons for doing this. The first and most important reason to us is that the application of heat to food makes it more easy to digest. Other reasons are that when cooked our food is more palatable; the process of cooking kills all microbes, which, if taken into our bodies alive, would give us diseases, and also it is easier for us to chew food that has been cooked.

This picture shows the construction of a successful electric lift magnet. This device, by means of magnetic attraction, fastens itself to practically all kinds of iron and steel without the aid of slings, cables or chains.]

The Story in a Magnet

What Makes an Electro Magnet Lift Things?

The working parts of an electric lift magnet are as follows:

A Shell.--This is a steel casting heavily ribbed on the top for strength, and also to assist in radiating the heating effect from the coil.

It is usually made circular in shape, the outside rim forming one pole, while the lug in the center forms the other. The coil fits in between these poles, thus making a magnet similar to the ordinary horseshoe type.

A Bottom Plate.--The under side of the magnet is closed by a very tough and hard non-magnetic steel plate, in order to protect the coil.

As well as being non-magnetic, this plate also has sufficient strength to resist the severe wear to which a magnet is necessarily subjected.

A Terminal Box.--A one-piece heavily-constructed steel casting bolted to the top of the shell, containing and protecting the brass sockets into which the wires from the coil terminate, forms the Terminal Box.

The sockets are made to receive plugs placed on the end of the conductor wire, by which the magnet is connected with the generator.

A Coil.--This consists of a round insulated wire which is passed, while being wound, through a cement-like substance, heavily coating each individual strand.

A low voltage of current is then passed through the coil, a sufficient length of time, to thoroughly dry out and bake the coating. This renders the magnet absolutely fireproof, eliminating all danger of short circuiting of the coil.

When finished it is well taped to protect the outside wire from becoming chafed.

The coil is made slightly smaller than the inside dimensions of the shell and the remaining space is filled with an impregnating compound, which hardens to the consistency of pitch.

This renders the coil thoroughly waterproof; also forms a cushion to prevent injury from the severe jars and shocks, received when dropping a magnet on its load.

A Controller.--The rapidity with which it is necessary to turn current on and off while operating a magnet, creates what is called a “back kick.” Unless this is dissipated quickly it is very destructive to the coil.