CHAPTER XIII.
WHY LEAD IS HEAVIER THAN CORK.
Monsieur Roger continued in these words:
"We say that a body has density when it is thick and packed close. Wegive the name of density to the quantity of matter contained in a bodyof a certain size.
"Let us suppose that this bit of lead has the same bulk--that is to say,that it is exactly as big--as the cork. Suppose, also, that we have apiece of gold and a piece of stone, also of the same bulk as the cork,and that we weigh each different piece in a pair of scales. We wouldfind that cork weighs less than stone, that stone weighs less than lead,and that lead weighs less than gold. But, in order to compare thesedifferences with each other, it has been necessary to adopt a standardof weight.
"I now return to Miss Miette's question,--'Why is lead heavier thancork?'--a question to which I had solemnly answered, 'Because itsdensity is greater.' Miss Miette must now understand that cork, weighingfour times less than water, cannot sink in water, although that processis very easy to lead, which weighs eleven times more than water. Andyet," said Monsieur Roger, "the problem is not perfectly solved, and Iam quite sure that Miss Miette is not entirely satisfied."
Miss Miette remained silent.
"I was not mistaken. Miss Miette is not satisfied," said Monsieur Roger;"and she is right,--for I have not really explained to her why lead isheavier than cork."
Miss Miette made a gesture, which seemed to say, "That is what I wasexpecting."
"I said just now," continued Monsieur Roger, "that the density of a bodywas the quantity of matter contained in this body in a certain bulk. Nowdoes Miss Miette know what matter is?"
"No."
"No! Now, there is the important thing: because, in explaining to herwhat matter is, I will make her understand why lead is heavier thancork."
"Well, I am listening," said Miette.
And Master Paul respectfully added, in an undertone, "We are listening."
Monsieur Roger continued:
"The name of 'bodies' has been given to all objects which, in infinitevariety, surround us and reveal themselves to us by the touch, taste,sight, and smell. All these bodies present distinct properties; butthere are certain numbers of properties which are common to all. Thoseall occupy a certain space; all are expanded by heat, are contracted bycold, and can even pass from the solid to the liquid state, and from theliquid to the gaseous state. They all possess a certain amount ofelasticity, a certain amount of compressibility,--in a word, there existin all bodies common characteristics: so they have given a common nameto those possessing these common properties, and called that whichconstitutes bodies 'matter.' Bodies are not compact, as you may imagine.They are, on the contrary, formed by the union of infinitely smallparticles, all equal to each other and maintained at distances that arerelatively considerable by the force of attraction.
"These infinitely small particles have received the names of atoms ormolecules. Imagine a pile of bullets, and remark the empty spaces leftbetween them, and you will have a picture of the formation of bodies. Imust acknowledge to you that no one has yet seen the molecules of abody. Their size is so small that no microscope can ever be made keenenough to see them. A wise man has reached this conclusion: That if youwere to look at a drop of water through a magnifying instrument whichmade it appear as large as the whole earth, the molecules which composethis drop of water would seem hardly bigger than bits of bird-shot.Still, this conception of the formation of bodies is proved by certainproperties which matter enjoys. Among these properties I must especiallysingle out divisibility. Matter can be divided into parts so small thatit is difficult to conceive of them. Gold-beaters, for instance, succeedin making gold-leaf so thin that it is necessary to place sixty thousandone on top of the other to arrive at the thickness of an inch. I willgive you two other examples of 'divisibility' that are still morestriking. For years, hardly losing any of its weight, a grain of muskspreads a strong odor. In a tubful of water one single drop of indigocommunicates its color. The smallness of these particles of musk whichstrike the sense of smell and of these particles of indigo which colorseveral quarts of water is beyond our imagination to conceive of. Andthese examples prove that bodies are nothing but a conglomeration ofmolecules. Now, if lead is heavier than cork, it is because in an equalvolume it contains a far more considerable quantity of molecules, andbecause these molecules are themselves heavier than the molecules ofcork. And now I shall stop," said Monsieur Roger, "after this long butnecessary explanation. I will continue on the day when Miss Miette willpresent to me the famous air-pump."
"That will not be very long from now," said Miss Miette to herself.
In Search of a Son Page 13