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balls of caoutchouc, which of late years have been mtroduced as parlortoys for children, rebound from the objects they strike by the spring ofthe air they contain. In the boy’s pop gun, that is formed of a quill, thetiny pellet is sent on its harmless errand by the elastic energy of the com-pressed fluid. And in the air gun, it is the elasticity of the same fluidthat projects balls with the force of gunpowder. If it were not elastic,people when fanning themselves would feel it thrown against their per-sons like water or sand. The act of inhaling it would be painful, for itwould enter the ehest by gluts, while its pulsations in sound would quicklydestroy the membranes of the ear.
Perhaps nothing is better calculated to expand our ideas of the proper-ties of matter, and of the wonders of Creation, than the compressibilityand dilatability of air. From the last named quality, it is probable thatthere is no such thing in nature as an absolute vaeuum ; and the best ofour air pumps can scarcely be said to make even a rüde approximationto one ! Those, whose knowledge of nature is confmed to impressionswhich things make on their senses, may suppose that the extremes of so-lidity may be found in a pig of lead and a bale of spunge; although theformer is, in all probability, as full of interstices as the latter ; and suchpersons could with difficulty be made to believe, that the entire mass ofmatter (air) which fills a space so immeasurably large as to baffle all cal-culation could be compressed into a lady’s thimble, and even squeezed in-to a liquid drop, so minute, as scarcely to be perceived at the end of aneedle.
Like all other matter with which we are acquainted, air has weight.This property is not naturally evident to our senses, but it may easily berendered so. By accurately weighing a bladder when filled with air andafterwards when empty, it will be found heavier when full. This wasan experiment of the ancients, but the moderns have ascertained its de-finite weight. A cubic foot of it, near the earth’s surface, weighs about1J ounces or -g-— part that of water, a cubic foot of the latter weighing1000 ounces ; hence the expression “ water is 800 times heaver than air.”The aggregate weight of the atmosphere has been calculated at up-wards of 77 billions of tons, being equivalent to a solid globe of lead 60miles in diameter ; hence its -pressure , for this enormous weight reposesincessantly upon the earth’s surface, and upon every object, animate orinanimate, solid, liquid, or aeriform. The pressure it thus exerts, (in allplaces that are not greatly elevated above the level of the sea) is equal toto about 15 Ibs. on every superficial square inch. Thus an ordinary sizedperson exposes so large a surface to its influenee, that the aggregate
water alone, for the liquid in the bag adapts itself to the uneven surface of the body, andsupports every part reposing upon it, with a uniform pressure. Water beds were how*ever known to the ancients, for Plutarch (in his life of Alexander) States that the peoplein the province of Babylon slept during the hot months, “ on skins filled with water.”
The luxury of the ancients with regard to beds was carried to a surprising ex-tent. They were of down, of the wool of Miletus , and sometimes stuffed with pea-cock r s feathers. The Romans had linen sheets, white as snow, and quilts of needlework, and sometimes of cloth of gold. Bedsteads among the rieh Greeks and Romanswere sometimes of ivory, of ebony, and other rieh woods, with inlaid work, and figuresin relief. Some were of massive silver, and even of gold, with feet of onyx. Theyhad them also of iron. One of that material was found in Pompeii . The earliest me-tallic bedstead mentioned in history is that of Og, king of Bashan. The Persians hadslaves expressly for bed making, and the art became famous in Rome . Golden bedsoften formed part of the plunder which the generals exhibited at their triumphs. TheAthenians put Timagoras their ambassador to Persia to death, for accepting presentsfrom the king, among which was a “ magnifieent bed with servants to make it.” Phf-tarch in Pelopidas.