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the spetific Gravities of Bodies.

the king, that he had found a method by which he could discoverwhether there were any cheat in the crown. For, fine* gold is theheavieff of all known metajs, it rmist be of lefs bulk, according to itsweight, than any other metal. And therefore, he desired that a massof pure gold, equally heavy with the crown when weighed in air,fhould be weighed against it in water; and- if the crown was not allay-ed, it would counterpoise the mass of gold when they were both im-mersed in water, as well as it did when they were weighed in air. Butupon making the trial, he found that the mass of gold weighed muchheavier in water than the crown did. And not only so, but that, whenthe mass and crown were immersed feparately ih one veflel of water, thecrown raifed the water Mych. higher than the malis did-; which Ihewed itto be allayed with forne lighter metal that increased- its bulk. And fo, bymaking trials with different metals, ali equally heavy with the crownwhen weighed in air, he found out the quantity of allay in the crown.

The fpecisic gravities of bodies are as their weights, bulk forbulk; thus a body is faid to have two or three times the fpecisicgravity of another, when it contains two or three times as muchmatter in the fame fpace.

A body immersed in ä fluid will sink to the bottom, if it be hea-vier than its bulk of the fluid. If it be suspended therein, it will loseag much of what it weighed in air, as its bulk of the fluid weighs.Hence, all bodies of equal bulk, which would sink in fluids, loseequal weights when suspended therein. And unequal bodies lose inproportion to their bulks.

The hydrosta- The hydroftatic balance differs very Uttle from a common balance thattte balance. nicely made: only it has a hook at the bottom of each fcale, onwhich small weights may be hung by horse-hairs, or by silk threads.So that a body, suspended by the hair or thread, may be immersed inwater without wetting the fcale from which it hangs.

How to find If the body thus suspended under the fcale, at one end of the ba-gravfty'of'any ^ ance > sirfl counterpoiscd in air by weights in the opposite fcale, andfcody. then immersed in water, the equilibrium will be immediately destroy-ed. Then, if as much weight be put into the fcale from which thebody hangs, as will restore the equilibrium (without altering theweights in the opposite fcale) that weight which restores the equili-brium, will be equal to the weight of a quantity of water as big as theimmersed body. And if the weight of the body in air be divided bywhat it loses in water, the quotitnt will fhew how much that bodyis heavier than its bulk of water. Thus, if a guinea suspended in air,be counterbalanced by 129 grains in the opposite fcale of the balance ;

and