ONCE upon a time a man is reported to have said: "Don't tell me that the world goes round. I know better. 'Cause why? When I get up in the morning I see the very same view all round as when I went to bed."

That man, at all events, thought for himself, which is better than not thinking at all, even though his thinking led to a mistaken conclusion. And the reasoning was not out of place. Nay, he had hold of an important truth; only he used that truth wrongly.

He grasped the fact that a man, going from one spot to another, must from time to time have different things about him. If he walks the changes come slowly; if he travels by train they arrive more quickly. In any case he cannot pass onward, hour after hour, moving among objects which do not move, and still see the same houses, the same trees, the same fields, the same hills. As he advances, he leaves the old surroundings behind, and finds himself amid new surroundings.

The man, of course, knew this. Though not learned in scientific matters, he had his share of common sense. When somebody told him that our solid old world was not, as he supposed, quietly at rest, but was incessantly twirling like a teetotum, he began to use his common sense.

He knew that when he went to bed at night he could see certain objects in the country around; and he knew that when he woke up in the morning he would find those same objects, each in exactly the same position. Then he put two and two together, and decided that the notion of the Earth spinning must be a mistake. "Don't tell me," he said. "I know better!"

And all the time he was himself making a curious mistake. Up to a certain point his reasoning was not incorrect; but he looked in the wrong direction for the changes of scene which he rightly considered ought to come about. And rather oddly, while taking it for granted that he would move with the moving Earth, he does not seem to have faced the probability that other objects on Earth's surface would do the same.

It never occurred to him that not only his own little house and garden, and everything in them, but other houses with all that they contained, and trees and fields, hedges and ponds, hills and valleys—one and all must be carried onward just as fast as the surface of the Earth was moving. Otherwise, if everything were left behind by that rushing surface, it would mean a complete and terrific jumble of destruction.

Naturally, therefore, the view before his eyes each morning had to be the same as his view of the evening before.

When a man in a railway carriage is borne along at the rate of fifty miles an hour, all that is inside that carriage travels at the same pace. The cushions, the seats, the people, the luggage, the fly on a window-pane, the air which fills the compartment, are journeying at fifty miles an hour. And when a traveller wishes to find a changing scene, he must not fix his gaze on the floor, or the seats, or on a fellow-traveller. He must look outside at the fields, the trees, the houses, the villages, seen through the windows.

This is just what one on Earth must do, if he would discover the movements of our globe from changes in the scenery. He must look right outside, away from Earth altogether; not at the things on our world, which move with the Earth as he does himself. And that is exactly what the man did not do. He looked only at the things around, all journeying with himself; and he forgot to gaze away outside, away from the hurrying surface of the solid globe on which he stood.

"Ah, yes," perhaps you may say. "He ought to have looked right off from everything on the ground. He ought to have watched the clouds. Then he would have understood."

No; not even then. That would have meant a second mistake on his part.

It is true that he would not, usually, find precisely the same clouds as the evening before; because clouds are perpetually altering their shapes, melting away, re-forming, taking new outlines. But these changes in them would be real. They would not be seeming changes, brought about by his own movements.

The clouds would have travelled onward, as he did

himself, with the Earth's surface. They might be blown hither and thither by currents of air; but as a whole they would have been carried from west to east by the steady whirl of the entire atmosphere, which moves with the surface of the Earth.

So if the man wished to get a really outside view, he would have to look beyond the clouds, beyond the great deep ocean of air, which really is a part of our Earth. He would have to lift his gaze into the sky, where float the Moon and Sun, the planets and the stars. Then at last he would find scenery which seems to change, like the objects noticed out of a rushing train, objects which often cannot but seem to move, if this world really does move, because they are not a part of the Earth, as air and clouds, hills and towns, fields and rivers and

oceans are.

"Now glowed the firmament

With living sapphires; Hesperus, that led
The starry host, rode brightest, till the Moon,
Rising in clouded majesty, at length
Apparent queen unveiled her peerless light,
And o'er the dark her silver mantle threw."

MILTON: Paradise Lost.

II. -HEAVENLY BODIES.

The first and simplest idea which a child generally has of Earth and sky is of a wide, flat plain, and of a fixed sky above, with clouds and a sun in it by day, and a moon and stars in it by night. Stars always at night, when the sky is clear; and a sun always by day, unless hidden by clouds; but a moon not always after dark.

So much as this an intelligent child might be expected to find out for himself, even if not told. And the first men who inhabited this Earth must have seen such things very much as an untaught child now would see them. Probably this was the idea in the mind of the man who could not believe that the Earth revolved.

Eut suppose that, instead of making up his mind in such a hurry, he had taken time to watch and to think. Suppose he had glanced away from Earth to the heavens, far beyond cloudland; had looked, not once or twice only, and not carelessly, but day after day with attentive and earnest eyes. Suppose he had kept this up, week after week, month after month, even year after year, trying to find out what changes in that heavenly scenery might mean.

He would see what already he knew-that the Sun each morning comes up from below the easterly horizon, crosses the sky, higher up or lower down at different seasons, and goes down below the westerly horizon.

He would notice that the Moon by night, when visible, does much the same; rising somewhere in the east, crossing part of the sky, and setting somewhere in the

west.

He would find the stars also to be on the move; many of them, like the Sun and Moon, rising in an easterly direction, crossing the sky, and setting in a westerly direction, while a certain number towards the north are never seen from our part of the Earth to set, but keep circling round and round a certain point.

Then, if left to himself, with no books or teachers, and no help from the thousands of years during which other men before him have watched and waited and