all close to each other, and close to us, and there is no need of ships;
we can exchange hand to hand."

But here comes a difficulty. Read carefully, and I think you will
understand it. Here is Ruth, a little growing girl, who wants phosphate
of lime to build bones with; for as she grows, of course her bones must
grow too. Very well, I answer, there is plenty of phosphate of lime in
the earth; she can have all she wants. Yes, but does Ruth want to eat
earth?--do you?--does anybody? Certainly not: so, although the food she
needs is close beside her, even under her feet, she cannot get it any
more than we can get the French goods, excepting by means of the
carrying trade. Where now are the little ships that shall bring to Ruth
the phosphate of lime she needs, and cannot reach, although it lies in
her own father's field? Let me show you how her father can build the
ships that will bring it to her. He must go out into that field, and
plant wheat-seeds, and as they grow, every little ear and kernel gathers
up phosphate of lime, and becomes a tiny ship freighted with what his
little daughter needs. When that wheat is ground into flour, and made
into bread, Ruth will eat what she couldn't have been willing to taste,
unless the useful little ships of the wheat-field had brought it to her.

Now let us send to the republic of the gases for some supplies, for we
cannot live without carbon and oxygen; and although we do breathe in
oxygen with every breathe we draw, we also need to receive it in other
ways: so the sugar-cane and the maple-trees engage in the carrying trade
for us, taking in carbon and oxygen by their leaves, and sending it
through their bodies, and when it reaches us it is sugar,--and a very
pleasant food to most of you, I dare say.

But we cannot take all we need of these gases in the form of sugar, and