As the earth spins round, the sun appears to rise sooner, the farther east we are, and to rise later, the farther west we are. So the apparent time, judged by the sun’s rising and setting, is different in different places, according as they are east or west of each other. Midday on one side of the earth is midnight on the other side.

So it is necessary to have some point from which to reckon our time, and the place on which many nations have agreed is Greenwich, near London, England. Countries have their own time for their own purposes; but for general purposes, as, for instance, events occurring in the sky, they refer to Greenwich time - that is to say, the time reckoned by what the sun seems to do at Greenwich. The lines on maps up and down the earth’s surface from north to south are called lines of longitude, or meridians. The spaces between them grow narrower as you go north and south of the Equator; and the lines meet at the poles. Places on the same line of longitude as Greenwich have Greenwich time exactly, and no other place can have it. That line is called the Greenwich meridian. Places east of that line are marked on maps so many degrees east longitude, and are sometimes spoken of as so many degrees east of Greenwich; and similarly for places west of the Greenwich meridian. Farthest east and farthest west of the Greenwich meridian is a single line that is both 180 degrees east and 180 degrees west of Greenwich. When it is noon at Greenwich, it is midnight along this line.

On top of a lofty hill, near Lake Wales, Florida, in a park and bird sanctuary, stands a beautiful tower 205 feet high, a shaft of color rising above the green of the surrounding forest. It is built of Florida stone and pink Georgia marble.

Round the tower at the top is a marble band on which are carved flamingos, cranes and other birds native to Florida. The grillwork at the windows represents animals and plants of Florida. The brass door tells the story of the world’s creation as it is reported in the Bible. Surrounding the tower is a moat, crossed by marble drawbridges and lengthening in front into a mirror-like pool.

In the tower are seventy-one beautifully toned bells forming one of the largest carilIons (sets of chimes) in the world. Four times a week the carillon-master gives public recitals and visitors come from all over the state to listen to these magnificent concerts.

The Singing Tower and the bird sanctuary in which it stands were presented to the people of the United States on February r, 1929, by Edward W. Bok, a philanthropist who started life as a poor immigrant boy from the Netherlands and rose to great wealth in America. Mr. Bok died in 1930, and lies buried in a crypt at the base of the tower.

If we look at the map of Egypt, we shall find the Nile, which is a very good example of a river with a delta at its mouth, and we shall notice how the river, when it meets the a, spreads out into a shape something like a triangle. Now that is the shape of the Greek capital letter D, the name for which is delta; and so land of this shape and origin made at the mouth of some rivers is called a river delta.

A river consists of moving water, and the motion of the water has power to rub away m the bed and the banks of the river a large quantity of solid material. This is not melted or dissolved in the river water, but is carried down by it. Now, when the river water meets the sea, its pace slackens, because it is opposed by the weight of the sea water. The solid matter held in the river water is likely to sink and form a wide bed or bank of mud.

Deltas are nearly always found at the mouths of rivers that flow into lakes or into closed seas or sheltered gulfs, because these seas and lakes do not have strong currents or tides to carry away the solid matter. Deltas grow quite fast. The Mississippi River is depositing so much solid matter (sediment) at its mouth that the shore line is moving into the Gulf of Mexico a mile in about sixteen years.

The most interesting of the world’s great tunnels are those which go under rivers. One of the largest of these is the Hudson River Vehicular Tunnel, popularly known as the Holland Tunnel. It is one of the most remarkable engineering feats of our day. It consists of twin tubes 9,250 feet long, each having a roadway 20 feet wide. Traffic, running one way in each tube, is divided into two lanes, one for slow travel and one for fast. Trucks and commercial vehicles are usually sent on the slow lane so that passenger traffic need not be held to their rate of speed.

Before the tunnel was built, the only way in which a motorist could cross from New York to New Jersey, or vice versa, was by driving the car on a ferry and being ferried across the river. This was very slow both because a boat does not travel fast and because a ferry can carry only a few cars at a time. Traffic would collect at the dock and have to wait in line for the next boat, and on popular driving days, such as Sundays and holidays, it would sometimes be necessary to wait for hours to be taken across. It can easily be seen what a great help the tunnel is, as an automobile can go through in a few minutes.

The construction of such a long underwater tunnel involved many engineering problems, chief of which was the difficulty of keeping the tunnel free of the poisonous gases discharged from the motors. After many experiments, this was accomplished by building four ventilating stations, one at each end of the tunnel, one in the river near the New York side, and the other in the river near the New Jersey side. Fresh air is forced, by means of ventilating fans at each of these stations, into the tunnel through a lower air duct, from which it passes into chambers on each side of the roadway and then into the roadway itself. The fresh air causes the exhaust gases to rise and by suction they are carried off through the openings at the top.

Lined with white glazed tiles, kept beautifully clean, the interior presents a very pleasing appearance. Along one side is a narrow railed walk where watchmen are on duty at all times of the day and night to direct traffic and to help any motorist who is forced to stop.

The tunnel was named in honor of Clifford M. Holland, the chief engineer who successfully planned and directed the work until his death, when the tunnel was nearing completion. It was first opened November 13, 1927. Over 52,000 automobiles passed through it on that day.

It was not long before traffic between New York and New Jersey grew too heavy for the Holland Tunnel to serve all of it. On October 25, 1931, the great George Washington Bridge was opened, and in December, 1937, another tunnel, the Lincoln, began to take some of the stream of cars. On the pages that follow we show you pictures of various kinds of tunnels.