tinued to float about for several seconds: he then drew in his breath, and caught it with much address on one of its points; and in this manner, alternately floating and catching it, did he continue to delight the wondering group for several minutes.

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Tom received the tube and ball from the hand of his father, and soon succeeded in playing with it. Observe, gentle reader, the address with which the boy manages it.

"This reminds me of my pea-shooter," said Tom, as he removed the tube from his mouth," with which I have often shot a pea across the play-ground."

Exactly; and you will now understand the nature of the force by which your pea was projected. The air blown from the lungs, gains such momentum from the contracted channel in which it flows, as to impart considerable velocity to the pea placed within the influence of its current."

Mrs. Seymour observed, that she had lately read in Waterton's "Wanderings in South America," a very interesting account of the Indian blow-pipe, which the natives of Guiana employ as an engine for projecting their poisoned arrows, and which owes its power to the principle of which Mr. Seymour had just spoken, and its unerring accuracy to the skilful address of the Indian who uses it. (12.)

"Mr. Seymour," said the vicar, "I much like your experiment with the pith-balls; but do tell me the use of the pins that are passed through them."

"They are not absolutely necessary for the success of the experiment; indeed, I ought to have stated, that their only use is to ensure the elevation of the ball to a certain distance above the orifice of the tube, before it is set adrift."

"Ne turbata volent rapidis ludibria ventis,' as Virgil has it. I duly appreciate the contrivance; but if the ball was set off at a distance from the orifice, such an expedient would be unnecessary."

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Certainly," answered Mr. Seymour; "I will soon convince you that, under the condition you propose, the pins are not essential."

So saying, he placed the tube in his mouth, and by carefully holding the ball at a distance of about half an inch from its orifice, he was enabled to consign it at once to a continous and steady stream of air, which can never be commanded at the point from which the air issues; and he thus succeeded in sustaining the ball in motion, in the same manner as he did in the preceding experiment.

"We will now proceed to the orchard," said Mr. Seymour," where I have prepared another pleasing exhibition of a similar description."

Within

The party accordingly left the Lodge, and when they had arrived at the fountain, their father produced a small wooden figure, of which the annexed is a sketch. its base was fixed a hollow sphere, or ball of thin copper, which when properly adjusted on a fountain, or jet d'eau, was sustained by the momentum produced by the velocity of the stream; so that the whole figure was balanced, and made to dance on the fountain, as the pith-ball had been made to play in the current of air.

The children were much gratified at witnessing so curious an exhibition. Mr. Twaddleton laughed heartily at the ludicrous effect it produced, and observed that, although he had never before seen the experiment, he had frequently heard of it; and he added, that he understood it to be a very common toy in Germany and Holland.

"I have for some time," said Mrs. Seymour, "been trying to construct a light figure of this kind, which shall dance on a current of air; and I believe I have at length

succeeded. The head I have formed of the seed-vessel of the Antirrhinum, which has a striking resemblance to a face, and possesses, moreover, the indispensable condition of lightness. The dress is made of silver paper, stretched over a cone of the same material. From its appearance I have named it the Flying Witch."

"I admire your ingenuity," said Mr. Seymour, "and I have no reason to doubt the success of your enterprise."

"I found it convenient," continued Mrs. Seymour, "to place a stage of card below the orifice of the tube, in order to steady the figure as she rises, and to receive her as she falls."

"Your principal care," observed her husband, “must be to throw the centre of gravity of the figure as low as possible, and which you may readily accomplish by shot suspended by silken strings from the base of the figure."

On the party returning to the library, Mr. Seymour expressed a wish that, before they suspended their morning's recreations, they should take into consideration a peculiar property of matter, which they had not yet discussed. "And what may that be?" asked Louisa.

"ELASTICITY," replied her father; " and I wish to hear whether Tom can explain to us the meaning of the term.' Tom very well knew what was meant by Elasticity; but he was like many a merchant with a bill of exchange, who, although well acquainted with its value, has not sufficient small change to cash it. Tom wanted words to enable him to furnish a clear definition; his father, therefore, kindly relieved his embarrassment, by informing him that "it was a property inherent in certain bodies, by which they possessed a disposition to have their form altered by force or pressure, and to recover it on the removal of that pressure, throwing off the striking body with some degree of force for example," continued he, "the cane which I hold in my hand can be bent to a certain extent, and then, if I let it go, it will immediately return to its former condition with considerable force."

Louisa inquired whether bending and pressing upon a body were the same thing. Mr. Seymour replied, that the form of an elastic body might be altered either by compression or distension, and that bending was, in fact, only a combination of these two methods; "for," said he, "when a straight body, like my cane, is bent, those particles of it which are on the one side are compressed, while those on the other are distended. But let us proceed with the subject. I have said that elastic bodies, on returning to their original form, throw off the striking body with some degree of force. I have here," continued Mr. Seymour, taking out of his pocket a wooden image of a cat, a toy which I intend as a gift to John; it will serve to illustrate our subject. The tail, you perceive, is moveable, one of its ends being tied to a piece of catgut, which is a highly elastic substance. When I bend the tail under the body of the animal, I necessarily twist the string; and by pressing the other end of the wooden tail upon a piece of wax, I can retain it for a few seconds in that situation."

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Mr. Seymour, having fixed the tail in the manner above described, placed the wooden image on the ground, when, in a few seconds, it suddenly sprang forward, to the great delight of the younger children.

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"Can you explain this action?" asked Mr. Seymour. "The wax," answered Tom, was incapable of holding the end of the tail longer than a few seconds; and as soon as it was let loose, the elasticity of the catgut enabled it to return to its former condition; in doing which the tail struck with force against the ground, which threw off the body of the cat and produced the leap."

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Very well explained; and you, no doubt, will readily perceive that the operation of steel springs depends upon the same principle of elasticity: a piece of wire or steel, coiled up, may be made to set a machine in motion by the endeavour it makes to unbend itself. This is the principle of the spring in a watch. When our watches are what is

termed down, this steel has uncoiled itself; and the operation of winding them up, is nothing more than that of bending it again for action (13). If the elasticity of a body be perfect," added Mr. Seymour," it will restore itself with a force equal to that with which it was compressed. As I have given John a toy, it is but fair that I should reward you, Tom: open that box, and examine the gift which it contains"

Tom received the present from his father, and proceeded to open the lid, when, to his great astonishment, the figure of an old witch suddenly sprang upwards. Mr. Seymour explained its mechanism, by stating "that the figure contained a wire coiled up like a cork-screw, and which, upon the removal of the pressure of the lid which confined it, immediately regained its original form." (14)

Tom inquired what kind of bodies was most elastic. He was informed that the air was the most elastic of all known substances, and had, for that reason, been distinguished by the name of an elastic fluid. Hard bodies were so in the next degree; while soft substances which easily retain impressions, such as clay, wax, &c., might be considered as possessing but little elasticity.

"I should have thought," said Louisa, "that neither clay nor wax had possessed any elasticity."

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My love, we know not any bodies that are absolutely, or perfectly, either hard, soft, or elastic; since all partake of these properties, more or less, in some intermediate degree. Liquids are certainly the least elastic of all bodies; and, until lately, water was regarded as being perfectly inelastic; but recent experiments have shown it capable of compression, and of restoring itself to its original bulk, as soon as the pressure is removed; it must, therefore, possess some elasticity. Indeed," said Mr. Seymour, "we might have anticipated such a result from the effects which present themselves in the well-known game of Ricochet,' or Duck and Drake."

6

The comparative inelasticity of water will be shown hereafter.