showed the powerful lamp within with its numerous wicks. Then the keeper touched something, and a large bronze framework outside of the glass barrel, containing red panes of glass set at certain intervals, be

gan to revolve so as to make red beams of light shine forth at certain short periods of time.

After they had examined the light all they desired, the keeper brushed off a few little specks of dust with a piece of soft chamois skin, and put on the cover, exclaiming, "She is a darling. We have to handle her with gloves."

All the visitors stepped out upon the balcony which surrounds the tower, and obtained a fine view of the coast and sea. They could see two persons near the stern of the "Verbena," who they thought must be Mrs. Cartmell and Miss Gray.

Mr. Cartmell thanked the keeper for his kindness, and they all returned at once to the yacht.

"Now, Papa, you must explain to us about the arrangement of the lantern which we have seen in the lighthouse," said Florence, "for I don't understand it at all."

Focus of...

Dioptric Apparatus
Burner, 7Wicks

"I will try to, if you and the others will gather round. "Years and years ago a little boy was born in a small town in France, who was destined to become one of the best friends sailors ever had. When he was eight years old he did not know his letters, because he disliked bookknowledge. But on the other hand, he was very fond of making experiments, especially in natural philosophy. This kind of study induced his parents to send him to a celebrated school in Paris, where he applied himself so earnestly that he rose step by step till he became an engineer; and soon afterward, in 1819, he won a valuable prize in writing an essay on light."

Micrometer

Valve

Pumps

Trimming

Strainer

Overflow Pipes

Floor

26 GALLON PRESSURE LAN

Supply Pipes.

line

Stage

26 GALLO

PRESSURE L

Weighted
Plunger

Moveable hedl

Pumps

of Lanter

LAMP AND OIL SUPPLY.

"Well, Papa, I don't see what this has to do with yonder lighthouse."

"You will soon see, Miss Impatience! This young

man's name was Fresnel, and he invented a way to make a lamp to be seen at a great distance from a lighthouse. In the first place he improved the lamp, so that there are four or five concentric wicks, one within the other, supplied with abundance of colza or kerosene oil by a pump moved by machinery, or from a reservoir of oil elevated above the wicks, and able to burn for twelve hours or more without being touched. You all saw this lamp inside the 'lantern."" "Why is there so much glass around the lamp?”

"Here is where Fresnel made his greatest invention. The object of that barrel of glass, of so many lenses, is to make all the rays of light going out from the lamp go forth so as to illume the sea, and not the ground or water at the foot of the lighthouse, or the sky above it.

"This you will understand from a simple drawing of a lamp, and a part of the lenses surrounding it.1

"In the figure I am now sketch

ing on this paper, this part represents about one half of the round barrel of glass, cut directly down through, from top to bottom. This gives what is generally called a cross-section. The ends of the lenses, as it were, are shown, and they are triangular in shape. The glass barrel, you remember, was made up of a series of glass rings, or prisms, laid one on top of the other."

"I remember how it looked," exclaimed Fred.

LIGHTHOUSE LANTERN.

"The rays of light from the lamp go out to each of these lenses, as I now show by the dotted lines, and in passing through are bent, or turned from their first direction, so as to emerge in a horizontal direction, and shine out across the water in one broad band of light."

"Do the rays in this way light up that part of the ocean where they are most needed to prevent shipwreck?" Florence asked.

"Yes; the flame of the lamp is about five inches in height; 1 See cut on the next page.

but this wonderful glass barrel sends forth a band of light eight feet in height, which is frequently seen twenty miles away."

"What a wonderful invention! They ought to call the lens after Mr. Fresnel, who thought it out," said Mrs. Cartmell.

"That is just what the world everywhere as the Fresnel lens.

has done. It is known For a fixed light it was perfect. Another gentleman, Mr. Stevenson, made im

provements in the revolving lights so that the fixed white light would be darkened, then this would be followed by a brilliant white flash, and then the light would go out, and reappear in a few seconds. Sometimes the flash is a red light. Each lighthouse has its characteristic light. The Government prints a catalogue of all the lighthouses, showing the kind of light given out by the lamp. Each vessel always carries this catalogue, and thus a vessel lost

in a storm can usually tell where it is as soon as it can see a lighthouse."

By the time the interesting lesson about the lantern was finished, and all had returned to the upper deck, the "Verbena" had steamed along many a knot, and the party found themselves past the Seguin Island Light. The tower and the other buildings could be seen away to the stern, rising far above the highest point of the little island.

"What are all these schooners, Captain Graham?" "They are filled with ice, Master Fred. We are opposite the mouth of the Kennebec River, and these vessels are carrying the ice to Philadelphia, Baltimore, and Savannah."

"I remember the big ice-houses we saw on the banks of that river when we took the trip to the Woods of Maine."

A safe and pleasant harbor was presently found by Captain Graham between two islands, near Monhegan Light, to which he piloted the yacht.

LESSON XI.

AMONG THE LIGHTHOUSES.

Part II.

As soon as they had anchored near Monhegan Light, as described in the last lesson, Fred ran to his sisters, exclaiming, "We are all going ashore before supper. Come."

Mrs. Cartmell and Miss Gray were escorted by the gallant captain, while the children joined their father in the tour of inspection.