"Fred, can you tell me the difference between frogs and toads?" asked Norah. "They seem to me to be so much alike that I am sure I could not tell one from the other.""I think I can make it clear to you, Norah," said Fred. "We had a good lesson about these animals this morning.
"First, then, the toad is larger and more clumsily built than the frog. Its legs too are shorter, so that it cannot leap so far as the frog. The frog"s hind legs are usually quite four inches long, and he leaps with these long legs. The toad"s leap is only a very short jump. It is slow and awkward in its movements. The toad"s feet are not webbed, so that it is not such a good swimmer as the frog. It lives mostly on land, and goes to the water only in the spring to lay its eggs.""Then, too," said Will, "it is easy to tell a toad from a frog by the look of its skin. A frog has a smooth skin, but a toad"s skin looks as if it were covered with thick warts or pimples. The frog"s skin is either agreenish-yellow or brown above, and yellowish- white on the under parts. The general color of the toad"s warty skin is a blackish-gray, with an olive- green tint. The under parts are yellow. Frogs and toads both have moist skins, but the toad can throw out over its skin a white liquid which has a most unpleasant smell.""Many people used to say," said Fred, "that this liquid was a deadly poison, and because of that, no poor animal has been so cruelly treated as the toad. It is not poisonous, but it will make the tender skin smart if it touches it, and even a dog will quickly drop a toad if he takes one up in his mouth. I saw old Ponto do it once, and didn"t he howl and shake himself.""The frog has teeth in the upper jaw," said Will, "but the toad has no teeth at all. It has, however, a pair of well-grown ears, which the frog never has.
"The toad, like the frog, is a most useful animal in the garden. It preys upon grubs and vermin of all kinds-slugs, caterpillars, earwigs, beetles, worms- nothing comes amiss. Before winter approaches the toad leaves off eating, and hides itself away in a hole in the wall, or under a stone, where it lies torpid till the frost and snow are all gone.""Do you know, Norah," asked Fred, "that the little newts, or efts, or effets, which we find sometimes in the ponds and ditches, are all animals of the same kind as the frog and the toad? The newts, however, have tails, which frogs and toads never have."SUMMARY
The toad is larger, more clumsily built, and more awkward in its movements than the frog.
The frog is a swimmer. Its hind feet are webbed. The frog has a smooth skin.
The frog has teeth in the upper jaw. The frog leaps on his long hind legs.
The frog spends much of its time in the water. The toad has no web between its toes.
The toad has a rough, warty skin. The toad has no teeth.
The toad moves slowly, with short jumps.
The toad goes to the water only in the spring to lay its eggs.
Lesson 30
Gases
"I want you to think about the air again, Norah." said Fred.
"Oh yes," she cried, "we found out that air is an actual substance, which takes up space and has weight, like all other bodies.""We have talked about solid bodies and liquids," Fred went on, "but air is a thin, light substance, which we cannot even see. It is not like either a solid or a liquid.
"Teacher says there are many substances that are like air and differ from both solids and liquids. He turned on the gas-burner to show us one of them. There was nothing to be seen, but we could hear something rushing out of the pipe, and we soon smelt it, and we saw it catch fire when teacher put a match to it.""Oh, you mean the gas," said Norah.
"Yes, but its proper name is coal-gas, because it is made from coal," said Willie.
"All thin, light bodies like these," said Fred, "arecalled gases. Air is a gas, and the invisible vapor in the air is a gas-water-gas. Gases and liquids are alike in some things, but they differ in others.
"What happens when we turn on the faucet over the sink?""The water runs out," said Norah, "because liquids flow.""Can you tell me then why the gas rushed out when teacher turned the burner on?""Well, I suppose it is because the gas flows along the pipes," said Norah.
"Quite right," said Fred, "it does, and so gases and liquids both flow.""If you pick up the bellows and set them to work," said Will, "you will soon find that air flows, and you know, too, that the wind is only air rushing along.""Teacher made a gas, called carbonic acid gas," said Fred. "We had to take his word that the gas was in the bottle, for we could not see it. But it was very funny to see him pour it out like water from one vessel into another.""But I thought you said the gas was invisible," said Norah.
"So it is," replied Fred. "But teacher held a lighted taper between the two vessels, and told us to watch while he poured out the gas. This is a gas in whichno flame could live, and although we could not see it flow from one vessel to the other, we saw it put out the light as it flowed.
"So then a gas is like a liquid, because they both flow.
"Now think again. We catch water as it flows from the faucet. Could teacher have caught the gas in a pail as it flowed from the burner? No, it would be impossible to catch the gas, because gases always spread themselves out rapidly in all directions. Teacher says gases differ from liquids in having no surface.""Oh yes," said Norah, "and liquids always keep a level surface."SUMMARY
Gases are fluids-they flow. Liquids always keep a level surface, but gases have no surface. They spread themselves out in all directions.
Lesson 31