times buried at a depth of two or three feet; sometimes they lie on the surface. They follow the surface of the country through which they pass, climbing the steepest hills, over high mountains, descending into the valleys, and crossing wide rivers.1

"These great pipes pass over beautiful farms, through pleasant little towns and villages, across wild forests and

swamps. One line crosses the majestic Hudson, passes through Central Park and the heart of New York City, thence across the East River, to the refineries on Long Island.

"Lines run to Philadelphia, Pittsburg, Baltimore, Cleveland, and Buffalo. One company owns three thousand miles of iron pipe, and can remove eighty thousand barrels

of oil in a day. The wells are connected with these trunk lines by two-inch pipes.

"The oil would not move through the pipes without some force, owing to the friction against the side of the pipe; so large and very powerful pumps are used, and the oil has to be pumped into tanks, and then sent on through more of the pipe. The main pipes are made very strong, so as to resist great pressure. The pumping and moving of the oil goes on day and night.

"If the lines become obstructed or clogged in any way, a small instrument is used called a 'scraper.' It has a set of small knives set like the wings of a windmill, and the pressure from the pumps makes these knives revolve and forces the machine forward through the pipe. Men follow along the line, and keep within hearing of the instrument by the noise it makes. If it stops at any place that part of the pipe has to be removed."

The next day the boys and their father returned to Pittsburg. On their way back George asked about natural gas, and its use at present.

Mr. Cartmell said:

"Natural gas issues from the ground wherever oil or salt abounds. At one time it was regarded as a serious obstacle to a good and profitable oil-well. Sometimes it will come out of a well and catch fire and burn fiercely. A well at East Sandy, Pennsylvania, caught fire several years ago and resisted all efforts to extinguish it. It burned for over a year, lighting up the surrounding country. The rush of gas and flame, roaring like a cataract, could be heard for miles.

"Within a few miles of Pittsburg, Pennsylvania, are numerous natural-gas wells. The Delameter, in Butler

County, is a remarkable one; it is situated in a valley surrounded by mountains. Gas is taken from this well to furnish light and fuel for the entire neighborhood.

"A part of the gas is allowed to escape through a tube three inches in diameter. This escaping gas is lighted, and it produces a jet forty feet high which shoots forth with a roar that makes the hills tremble and sounds like a thousand locomotives blowing off steam at once.

"Near the flame the earth is scorched, but farther away the vegetation is abundant and resembles the tropics. In winter, ten acres about the well are covered with green grass. During a calm night, the noise of the great burning flame can be heard for fifteen miles."

"Isn't Pittsburg now lit with this gas, Papa?" Fred asked, as the train drew near to the city.

"Pittsburg is now illuminated with natural gas, and this product is largely used in place of coal for fuel in the iron and steel mills, in the manufacture of glass, and various forms of industry where power and heat are needed. The gas is brought about twenty miles. Pittsburg can no longer be called the Smoky City. Freeport, Alleghany, and many other places in Pennsylvania and in Ohio are using natural gas at present. How long the supply will last we do not know.”

LESSON VII.

COAL MINES.

A FEW days later the Cartmells left Pittsburg for Philadelphia. They were on the limited Chicago express, and after obtaining seats in the second coach, went back to the observation car in the rear of the train. Only a few per

COAL MAP.

sons were in the car at this time, so they obtained very good seats for seeing the scenery. The views as they passed through the Alleghany Mountains were very beautiful. The "Horseshoe Curve," however, excelled the other views in loveliness.

"I thought," said Fred, "that Pennsylvania was a great coal State, and yet I have not seen in this ride any mines. Where are they?"

"It is a great coal State," said his father. "You have seen thousands of carloads of coal on the way, but we have not been moving through mines of course, or very

near coal centres. You know that the soft coal is found in great abundance in the western part of the State, and hard coal in the northeastern part. The United States has large areas of coal, as this coal-map plainly indicates."