This is assuming that the ball were acted upon by no force other than that of gravity. If it encountered resistance, say that of air, it would finally come to rest at the earth's centre, and there it would remain, without visible support, being attracted by the earth's mass with equal force in every direction.

That this would be the result will become apparent upon examining the circumstances of the case. To begin with,

there can be no question that the ball I would fall to the earth's centre. The force which drew it downward would not be a constant one, however, but one continually lessening in intensity until, at the earth's centre, it became nil. The reason of this is that when the ball was below the earth's surface the portion of the earth's mass which lay above it would attract it upward, and only the portion which lay below it- that is, below a plane passing through it perpendicular to the direction of its fallwould attract it downward. The relative intensities of these two attracting forces can be calculated for any given position of the ball. The force which would be efficient for drawing the ball downward would be, of course, their difference. Without attempting to give here the demonstration, the simple fact may be stated that at every point in its descent the ball would be pulled downward by a force proportional to its distance from the earth's centre. At the start the whole force of gravity would act in a downward direction, giving to the ball an acceleration of thirty-two feet a second. When it had reached a point midway between the earth's surface and its centre, the acceleration would be sixteen feet a second. At three-quarters of the way down it would be reduced to eight feet a second, and at the centre it would become zero.

The ball would descend with accelerated velocity and would reach the earth's centre with a velocity of about five

miles a second. Its momentum would carry it past this point, and its course would then become one of ascent from the centre. Now would come in the principle that to stop a moving body requires the same expediture of force as that which gave it its motion. The only force operating in this case would be that of gravity, which would now pull at the upward-flying ball, to check its motion, with exactly the same intensity and under the same conditions as when it was drawing it downward. As a consequence, the ball would rise before it parted with all of its motion to a height exactly equal to that from which it fell. It would rise to the surface of the earth on the farther side, where it would rest for a brief space of time, and then, gravity still having a hold upon it, it would fall back towards the earth's centre, again shoot past that point, and, ascending on the other side, would return to the point from which it fell originally.

The movement of this ball is essentially the same as that of a swinging pendulum. Now, if a pendulum is struck dexterously when just at the end of its swing, in a direction perpendicular to the plane in which it swings, it will be set to swinging in two ways simultaneously and its visible path will be an ellipse, or, if the blow is just sufficient to make it swing in the new direction to the same extent as in the first, the path will be a circle. This ellipse or circle will be described by the bob of the pendulum in the same time as it requires for making one complete oscillation. Similarly our cannon ball would make its double passage through the earth in the same time as it would take in circling round the earth, just clear of its surface, as a satellite. To escape falling to the earth, it would need to travel at the rate of a little more than five miles a second, and the period of its revolution round the earth would be one hour and twenty minutes, very nearly. G. S. J.

It is believed by many scientists who have followed most carefully the growth of the science of brain diseases, remarks a pharmaceutical journal, that scores of the deaths set down to other causes are due to worry, and that alone. The theory is a simple one-so simple that

any one can readily understand it. Briefly put, it amounts to this: Worry injures beyond repair certain cells of the brain; and the brain being the nutritive centre of the body, the other organs become gradually injured, and when some disease of these organs, or a combination of them, arises, death finally ensues.

Thus does worry kill. Insidiously, like many another disease, it creeps upon the brain in the form of a single, constant, never-lost idea; and as the dropping of water over a period of years will wear a groove in a stone, so does worry gradually, imperceptibly, but no less. surely, destroy the brain cells that lead all the rest—that are, so to speak, the commanding officers of mental power, health and motion.

Worry, to make the theory still

NOISE AS A DANGER SIGNAL.

N

OISE, says the "American Machinist," is, like dirt, a nuisance. Much noise, like much dirt, is a great nuisance. As dirt is matter out of place, so noise is sound out of place. Dirt demands removal, and so is the great promoter of cleanliness. Noise is perhaps more insistent than dirt, and so has also its beneficent function, especially in the running of machinery. For many of the improvements and much of the perfection of modern machinery, noise only is to be thanked. Noise has done and is constantly doing much for lubrication, from the squeaking wheel-barrow and the baby carriage to the line shaft or the loose pulley in the shop, and so clear to the top. Noise has saved the lives of half the steam-engines and of many engineers.

When things are running all right there will be sounds, generally rhythmical, and therefore more or less musical, but never noise. As soon as things go wrong, there is noise at once. The knock in the cylinder must be attended to or the head flies out. There are other noises about an engine which tell an engineer at once of minor disarrangements and give the opportunity of correction before wear or accident occurs. A deaf engineer would necessarily be an almost worthless and an unsafe one. Probably many persons do not appreciate the value of good hearing to an engineer. It is probable that

stronger, is an irritant at certain points, which produces little harm if it comes at intervals or irregularly. Occasional worrying of the system the brain can cope with, but the iteration and reiteration of one idea of a disquieting sort the cells of the brain are not proof against. It is as if the skull were laid bare and the surface of the brain struck lightly with a hammer every few seconds, with mechanical precision, with never a sign of a “let up" or the failure of a stroke.

Just in this way does the annoying idea, the maddening thought that will not be done away with, strike or fall upon certain nerve cells, never ceasing, and week by week diminishing the vitality of these delicate organisms that are so minute that they can only be seen under the microscope.

on our railroads there should be tests for hearing as well as for sight, although we have not heard of them. Sound is constantly telling the stationary engineer of the condition of his engine, and noise. tells of its maladjustment or derangement. Noise tells of the unwelcome presence of water in pipes and valve chests, as well as in the cylinder, of the incorrect action of valves, of abnormal changes of speed, of defective lubrication anywhere, of the displacement and rubbing of parts, of nuts or screws working loose, of connections or bearings that need taking up. An engineer that can hear noises in his engine room and be content under their continuance should be promoted to the outside of the door.

An ear sensitive to noise, with a proper detestation of it, is one good qualification for a foreman or superintendent. Noise means at least discomfort, makes men nervous and irritable, and will never allow them to do their best. We worked once for a long time contiguous to some rattling gearing, and we know what we are talking about. We passed through a foundry the other day where they had a very noisy power-driven sand shifter at work which must have had anything but a good effect on the men, and certainly did not increase the amount of work done, and we could not help wondering how the powers that be could permit such a nuisance. There are many preventable noises that might be stopped.

"The line of separation," she writes, "between the studies of a young man and a young woman is this:

A woman is excused from all professional knowledge. Men study in order to qualify themselves for the law, for physic, for various departments in political life, for instructing others from the pulpit or professor's chair. These all require a great deal of severe study and technical knowledge, much of which is in no wise valuable in itself, but as a means to that particular profession. Now, as a woman can never be called to any of these professions, it is evident that you have nothing to do with such studies. A woman is not expected to understand the mysteries of politics because she is not called to govern. She is not required to know anatomy because she is not to perform surgical operations; she need not embarrass herself with theological knowledge because she will neither be called upon to make or explain creeds.

"A woman should have such a tincture of general knowledge as to be able to engage gracefully in conversation. In no subject is she required to be deep, of none should she be ignorant. If she

knows not enough to speak well she should at least know enough to keep from speaking at all, and the modesty which prevents an unnecessary display of what she does know will cause it to be supposed that her knowledge is greater than it is. As she will never obtrude her knowledge, none will ever be sensible of any deficiency in it, and her silence will seem to proceed from discretion rather than from a want of information."

It is proper to state, in passing, that Mrs. Barbauld could not so clearly have stated the popular idea of woman's education had she not herself overstepped the boundaries she prescribes. She was an excellent classical scholar, but dared not counsel her niece to a like disregard of prevailing sentiment; hence, her letter, presenting as it does the compromise between this sentiment and a personal desire for intelligence, affords as perfect a key to the spirit of the time as we can hope to find.

In this whirl of contending influences began the life of Mary, daughter of Admiral Sir William Fairfax. She was born at Jedburgh, Scotland, in the year 1780, and disclosed at an early age a hunger for knowledge that changed the whole

direction of her life and made her the most remarkable woman of her time.

The memory of days which are in any respect remarkable acquires peculiar charm when viewed through the perspective of quiet years, and one experiences a unique pleasure in reading the personal recollections of this gifted woman. We learn how, as a child, she wandered along the seashore, collecting shells, pebbles and flowers; how she passed evenings in gazing at the starlit heavens; how she amused herself in a garden frequented by birds, observing them until their habits were familiar to her. The first ten years of her life were passed without the aid of books- unless we except the book of nature, whose leaves she was already beginning to turn.

This excellent foundation for the superstructure of wisdom seems to have been most unwittingly laid, and was in fact the result of neglect rather than prevision. Suddenly, however, her father awoke to a consciousness of the fact that a girl should at least know how to read and write and keep accounts, and Mary was sent away to school.

We learn from her record how, though perfectly erect and well formed, she was enclosed in stiff stays, with a steel busk in front, while bands drew her shoulder blades back until they met, and how another steel rod with a semicircle which passed under the chin was clasped to the busk in her stays. In this constrained attitude she had to prepare her lessons, and the chief task given her was to "learn by heart' daily a page of Johnson's Dictionary. She returned to her home at the age of eleven, and, aside from instruction in music, seems to have been left to her own devices. When thirteen years old, she for the first time met with a friend who encouraged and gave direction to her love for study.

A little later, while out in company with her mother, she met a lady who tried to interest her in some manner of fancy work. While turning the leaves of a book of designs her eye caught sight of what appeared to be an arithmetical question, but, on turning the page, she found strange-looking lines mixed with letters, chiefly x's and y's: Said her friend, replying to her eager inquiry: "It is a kind of arithmetic; they call it algebra. I can tell you nothing about it.'