spirits whom Milton represents as saying that ascent is their natural, and descent their unnatural, motion."*

"I have seen screens similarly constructed," said Mrs Seymour, "which always rose up of themselves, upon the removal of the force that had pressed them down."

"I will explain their principle," said Mr Seymour.

"Suppose we first examine the construction of the figure," observed the vicar. "Bless me! why it is like the poet Philotus of Cos, who was so thin and light, that lead was fastened to his shoes to prevent his being blown away." +

"The figure," said Mr Seymour, "is made of the pith of the elder-tree, which is extremely light, and is affixed to the half of a leaden bullet; on account, therefore, of the disproportion between the weight of the figure and that of its base, we may exclude the consideration of the former, and confine our attention to the latter. The centre of gravity of the hemispherical base is, of course, in its axis; and, therefore, tends to approach the horizontal plane as much as possible, and this can never be accom

plished until the axis becomes perpendicular to the horizon. When. ever the curved surface is in any other position, the centre of gravity is not in the lowest place to which it can

descend, as may be seen by the diagram which I have just sketched. If the axis a d be removed to c d, it is evident that the centre of gravity will be raised, and

that, if left alone, it would immediately descend again into its original position."

* The vicar here alludes to the speech | in vain, no such accommodation was to of Moloch ("Paradise Lost," b. ii., 1. 75):

'That in our proper motion we ascend Up to our native seat: descent and fall To us is adverse."

This story is related by Ælian, who at the same time discredits it, for, says he, "how could he carry about a sufficient weight to prevent his being blown away, if he were so weak as not to be able to resist the sea-breeze?" This matter-of-fact way of regarding a humorous fable is exceedingly amusing, and reminds the author of a somewhat similar criticism upon an American story which he had related. A traveller, after a long journey, anxiously looked about for some inn wherein his jaded horse might have a bait; but all

be found: his next attempt was to find a grassy spot that could afford some pasturage, but in this again he failed. In this dilemma his ingenuity suggested a resource, which proves, for the thousandth and first time, the truth of the old adage, that "Necessity is the mother of Invention;" drawing from his pocket a pair of green-glass spectacles, he placed them upon the horse's face, and led him into a carpenter's yard, when the deluded animal immediately commenced his meal upon the shavings of wood and sawdust. The absurdity of this story necessarily excited a general laugh, but with one exception; it was evident that one of the company did not sympathise with his companions, and after a few minutes of apparent abstrac

“I understand it perfectly," said Tom. "When the axis ad is perpendicular, the centre of gravity will be in its lowest point, or as near the earth as it can place itself; when, therefore, the figure is pressed down, the centre of gravity is raised, and, consequently, on the removal of that pressure, it will descend to its original position, and thus raise the figure." “I see you understand it. Here, then," continued Mr Seymour, “is another toy in further illustration of our subject. It consists of a small figure, supported on a stand by a ball, which is quite loose; and yet it is made to turn and balance itself in all directions, always recovering its erect position, when the force applied to it is removed. The two weights, in this case, bring the centre of gravity considerably below the point of suspension or support, and therefore maintain the figure upright, and make it resume its perpendicular position, after it has been inclined to either side; for the centre of gravity cannot place itself as low as possible, without making the figure stand erect."

"That is very evident," cried Louisa.

"I shall next exhibit to you," continued Mr Seymour, a toy that furnishes a very good solution of a popular paradox in mechanics; viz., A body having a tendency to fall by its own weight, how to prevent it from falling, by adding to it a weight on the same side on which it tends to fall."

"That is indeed a paradox!" exclaimed Louisa. "The next time I see the gardener sinking under the load of a heavy sack, I shall desire him to lighten his burden by doubling its weight."

"Will you, indeed, Miss Pert? I do not think so, after you have seen the operation of the toy I am now about to exhibit. Here, you perceive, is a horse, the centre of gravity of which would be somewhere about the middle of its body; it is, therefore,

tion, he exclaimed, with an air of much solemnity, "I must beg your pardon, sir, but I entertain strong doubts as to the truth of your story, for I cannot understand how the spectacles

could have been fixed on the horse's nose." So true is the saying, that "The prosperity of a jest lies in the ear of him who hears it."

very evident that, if I were to place its hinder legs on the edge of the table, the line of direction would fall considerably beyond the base, and the horse must be precipitated to the ground; you will, however, perceive that there is a stiff wire attached to a weight which is connected with the body of the horse, and by means of such an addition, the horse prances with perfect security at the edge of the precipice; so that the figure which was incapable of supporting itself is actually prevented from falling, by adding a weight to its unsupported end!"

The children admitted the truth of this statement, and were not immediately prepared to explain it.

"The weight, indeed, appears to be added on that side; but, in reality, it is on the opposite side," said the vicar.

"In order to produce the desired effect,” observed Mr Seymour, "the wire must be bent, so as to throw the weight far back, under the table; by which contrivance, since the centre of gravity of the whole compound figure is thrown into the leaden weight, the hind legs of the horse thus become the point of suspension, on which the ball may be made to vibrate with perfect security."

"Now I understand it," cried Tom; "instead of the weight supporting the horse, the horse supports the weight.”

"Exactly so. You perceive, therefore, from these few examples, that the balancer, by availing himself of such deceptions, and combining with them a considerable degree of manual dexterity, may perform feats, which, at first sight, will appear in direct opposition to the laws of gravity. There is also another expedient of which the balancer avails himself, to increase the wonder of his performances, and that is the influence of rotatory motion, which, you will presently see, may be made to counteract the force of gravity."

"I remember that the most surprising of all the tricks I witnessed was one, in which a sword was suspended on a key, which turned round on the end of a tobacco-pipe; on the top of the sword a pewter-plate was, at the same time, made to revolve with great velocity."

"I well remember the trick to which you allude. The rotatory motion prevented the sword from falling, just as you will hereafter find the spinning of the top will preserve it in an erect position. There is also another effect produced by rotatory motion, with which it is essential that you should become acquainted. You no doubt remember that momentum, or the velocity of a body, will compensate for its want of matter. A number of bodies, therefore, although incapable of balancing each other when in a state of rest, may be made to do so by imparting to them different degrees of motion. I believe that you are now acquainted with all the principles upon

which the art of balancing depends; and I have little doubt, should we again witness a performance of this kind, that you will be able to explain the tricks which formerly appeared to you so miraculous."

EARLY on Monday morning did the young group assemble in the library: they had been told by Mrs Seymour that their father had received a new toy of a very interesting and instructive nature, and we can easily imagine the eagerness with which they anticipated the sight of it.

"I trust," said Mr Seymour, "that after our late discussion, the subject of the centre of gravity is thoroughly understood by you all. I have also reason to think that the nature and effects of what is termed momentum have been rendered intelligible to you."

"I certainly understand both those subjects," answered Tom: and so thought the rest of the party.

"Well, then, I will put your knowledge to the test," observed Mr Seymour, "for you shall explain to me the mechanism of these Chinese Tumblers." Upon which he produced an oblong box, which, by opening, formed a series of stairs or steps, and took from a drawer at its end two grotesque figures, (Clown and Pantaloon.) which were connected with each other by two poles, which they appeared in the attitude of carrying, pretty much in the way that the porters carry the poles of a sedan-chair. The foremost figure was then placed upon the top step, when, to the great astonishment of the whole party, the figures very deliberately descended the several stairs, each turning over the other in succession.

"There was a period in our history," observed Mrs Seymour, "when

E