WRESTLING WITH A GYROSCOPE

IN 1852, a distinguished young Frenchman, Jean Bernard Léon Foucault (fö-kō), perfected an earlier instrument of Bohnenberger, and named it a "gyroscope." The piece of apparatus was doubtless made up for the physical laboratory, and had refinements not seen in the toys known to our boys and girls, which playthings the Century Dictionary tells us should properly be called, not "gyroscopes," but "gyroscopic tops." First invented as a classroom instrument, this interesting device is now under consideration for practical uses; incidentally, its odd pranks under certain circumstances prove a source of amusement and wonderment to old and young alike.

Imagine yourself a giant, big enough to hold the earth in your hands; under such circumstances, what do you suppose the action of the earth would be? It would be much the same as of a gyroscopic top, only on a very big scale. It would tend to hold itself in the plane of its rotation, and any attempt to move it at right angles to its motion, or in a plane from pole to pole, would be instantly resisted, giving a sort of a figure-eight motion. Indeed, it is a very good thing that the earth, in revolving around the sun, does keep its axis parallel to any one position, for that is what gives us our seasons.

The machine shown in the accompanying pic

The man in the photograph seems to be having hard work to master the "gyro," doubtless to the

amusement of the spectators, and no matter how big and powerful the man is, the result is always the same. In the picture showing the policeman trying to make the top lie flat, Mr. Montraville Wood, the aërial postmaster of Chicago, is also shown. Under Mr. Wood's deft touch the model does wonderful things; it will lie down, rise up and get on its feet, and turn around. A heavy weight placed on one side causes that side to rise, a most interesting experiment.

One day, when Mr. Wood was traveling in Iowa, where he had been demonstrating some of the gyro's wonderful feats, he discovered that it was about time to take his train. He locked the gyro up

in its trunk while it was still spinning, and delivered the trunk to the baggageman, who placed it on a truck with other trunks. The truck unexpectedly making a sharp turn in order to reach the baggage-car, was not at all to the liking

of the gyroscope, which jumped, trunk and all, nimbly to the platform! You can imagine the

The principle of the gyroscope might be, and indeed has been, readily adapted to some very interesting practical uses: to give stability to a monorail car or an aeroplane; to prevent seasickness on lake or ocean vessels by preventing excessive motion; to free ships from packed ice, by reversing the motion and causing the boat to rock and break the ice by this rocking motion.

The underlying principle of the gyroscopic top is very simple; when motion is imparted to a body, we feel safe in asserting that the body would continue moving in a straight path until

READY TO TAKE HOLD OF A GYROSCOPE
RUNNING AT THE RATE OF 3000
REVOLUTIONS A MINUTE.

surprise of the trainmen, who refused to have anything further to do with the trunk until Mr. Wood opened it up and removed the gyroscope. At another time, Mr. Wood gave a colored porter a traveling case containing a spinning

HE STILL HOLDS ON.

some force is applied to deflect it. In the case of a cannon-ball the mass is so great and the velocity so high that it would take a large effort to swerve it to one side. The fast-flying particles in the gyroscope wheel seem to obey a similar law, for it takes energy, sometimes quite a good deal of energy, to change their direction, and

HE REALLY THINKS HE HAS IT.

gyro to carry to his sleeping-car. All went well until they came to a corner, when the traveling case refused to turn, and all the efforts of the porter and the bystanders could not make it turn the corner. The porter finally dropped it at the feet of the owner, declaring that it was either full of snakes or bewitched.

THE DOMES OF YOSEMITE FORTUNATELY, one does not need to be a scientist in order to enjoy the beauties or marvels of nature. Though it is well worth while to learn what we can of the causes of things, and though the knowledge, if we have it, will but add to the wonder, there are many things about which wise people can only guess, after all. One of these is the strange, dome-like shapes of many of the

Sentinel Dome, almost as perfect in curve as if it had been turned in a lathe. El Capitan, too, when seen from the upper levels, shows a forehead that evidently was of the same shape as the others before the stroke occurred that formed the mighty cliff. Near the North Dome (the Indian name of which is To-ko-ya, or basket, from its likeness to a basket turned upside down) there stands another peak of similar shape. This also is known as Basket Dome; and, as one goes eastward, one finds mountain after mountain repeating this peculiar feature, until one comes to have a vision of Mother Nature, like a sort of housemaid, down on her knees, scouring away for ages at these rugged peaks, until she had rounded off their stony heads and brought them into a family likeness. In one case, for a novelty, she put a dome upon a dome, as you will see by the picture of the one in the Merced Cañon; and in another she has left a huge boulder, that must weigh many tons, neatly balanced on the very top of the round head of the mountain.

The geologists do not agree as to what caused these remarkable formations, so different from

THE DOUBLE DOME IN THE MERCED CAÑON.

mountains that surround the Yosemite Valley. No visitor to the valley can help being astonished at the sight of the great half-mountain of granite that is called Half Dome. The best idea of it which one could give to a blind person would be to say that it was like the half of a split apple set up on edge. Opposite to Half Dome is another mountain, called North Dome, that one might take to be the helmet of one of the Titans.

But when one climbs to the "rim" of the valley, and gets a full sweep of that vast granite upland in which the valley itself is a mere gash, one is astonished to find the same strange form repeated over and over. Close to the south edge is

FAIRVIEW DOME.

anything to be seen elsewhere in the world. Some say that the domes were formed by the action of glaciers, which slowly ground these masses down

from their original shapes; and it is plainly to be seen that glaciers have passed over them, from the polish left on the granite by the enormous pressure. Others say that the mountains, through some unusual circumstance, were thrown up in these shapes, almost as we see them, and that the glaciers hardly changed them at all. No one can tell. We can put two and two together, and say that they must make four; but, then, perhaps there is another one somewhere, that we do not know about, that would change it to five. If one were to go simply by appearance, one might easily think that the domes were nothing more nor less than great bubbles, thrown up here and there by the heat below while the granite was in a melted state, just as you have seen bubbles rise when some thick liquid was boiling. But whatever caused them, they are very noble and very beautiful forms, and the mystery of their making is but a small part of their wonder and grandeur. J. S. CHASE.

A BURNING OIL-TANK It is a spectacular and even awe-inspiring sight, in our great American oil-fields, when one of the storage-tanks, holding 3700 barrels of oil, gets on fire. As soon as such a fire is discovered, to prevent a greater conflagration a large force of workmen is called and begin throwing up a mount of earth known as a "levee" a few feet distant from the tank and completely encircling Then if the oil boils over, as it is likely to do, it, as shown in the accompanying photograph. the flames are prevented. from spreading by this earthen wall. Otherwise the fire would spread to other tanks, and eventually all over the fields.

As these tanks are usually in an exposed position rising high above surrounding objects, they form a strong point of attraction for lightning involving the loss of many thousands of dollars, during a thunder-storm, and many of these fires, have been caused in this way.

W. FRANK MCCLURE.