Comienzo · continuación 17

_Mr. An._ I suppose they were sand-pipers, one of the numerous family of birds that get their living by wading among the shallows, and picking up worms and insects.

_Will._ There were a great many swallows, too, sporting upon the surface of the water, that entertained me with their motions. Sometimes they dashed into the stream; sometimes they pursued one another so quick, that the eye could scarcely follow them. In one place, where a high, steep sandbank rose directly above the river, I observed many of them go in and out of holes with which the bank was bored full.

_Mr. An._ Those were sand-martens, the smallest of our species of swallows. They are of a mouse-colour above, and white beneath. They make their nests and bring up their young in these holes, which run a great depth, and, by their situation, are secure from all plunderers.

_Will._ A little farther I saw a man in a boat who was catching eels in an odd way. He had a long pole with broad iron prongs at the end, just like Neptune’s trident, only there were five instead of three. This he pushed straight down among the mud in the deepest parts of the river, and fetched up the eels sticking between the prongs.

_Mr. An._ I have seen this method. It is called spearing of eels.

_Will._ While I was looking at him, a heron came flying over my head, with his large flagging wings. He lit at the next turn of the river, and I crept softly behind the bank to watch his motions. He had waded into the water as far as his long legs would carry him, and was standing with his neck drawn in, looking intently on the stream. Presently, he darted his long bill as quick as lightning into the water, and drew out a fish, which he swallowed. I saw him catch another in the same manner. He then took alarm at some noise I made, and flew away slowly to a wood at some distance, where he settled.

_Mr. An._ Probably his nest was there, for herons build upon the loftiest trees they can find, and sometimes in society together, like rooks. Formerly, when these birds were valued for the amusement of hawking, many gentlemen had their _heronries_, and a few are still remaining.

_Will._ I think they are the largest wild birds we have.

_Mr. An._ They are of a great length and spread of wing, but their bodies are comparatively small.

_Will._ I then turned homeward across the meadows, where I stopped a while to look at a large flock of starlings which kept flying about at no great distance. I could not tell at first what to make of them; for they rose all together from the ground as thick as a swarm of bees, and formed themselves into a kind of black cloud, hovering over the field. After having a short round they settled again, and presently rose again in the same manner. I dare say there were hundreds of them.

_Mr. An._ Perhaps so, for in the fenny countries their flocks are so numerous as to break down whole acres of reeds by settling on them. This disposition of starlings to fly in close swarms was remarked even by Homer, who compares the foe flying from one of his heroes, to a _cloud_ of stares retiring dismayed at the approach of the hawk.

_Will._ After I had left the meadows, I crossed the cornfields in the way to our house, and passed by a deep marl-pit. Looking into it, I saw in one of the sides a cluster of what I took to be shells; and upon going down, I picked up a clod of marl, which was quite full of them; but how sea-shells could get there I cannot imagine.

_Mr. An._ I do not wonder at your surprise, since many philosophers have been much perplexed to account for the same appearance. It is not uncommon to find great quantities of shells and relics of marine animals even in the bowels of high mountains, very remote from the sea. They are certainly proofs that the earth was once in a very different state from what it is at present; but in what manner, and how long ago these changes took place, can only be guessed at.

_Will._ I got to the high field next our house just as the sun was setting, and I stood looking at it till it was quite lost. What a glorious sight! The clouds were tinged purple, and crimson, and yellow, of all shades and hues, and the clear sky varied from blue to a fine green at the horizon. But how large the sun appears just as it sets! I think it seems twice as big as when it is overhead.

_Mr. An._ It does so; and you may probably have observed the same apparent enlargement of the moon at its rising.

_Will._ I have; but pray, what is the reason of this?

_Mr. An._ It is an optical deception, depending upon principles which I cannot well explain to you till you know more of that branch of science. But what a number of new ideas this afternoon’s walk has afforded you! I do not wonder that you found it amusing: it has been very instructive, too. Did _you_ see nothing of all these sights, Robert?

_Rob._ I saw some of them, but I did not take particular notice of them.

_Mr. An._ Why not?

_Rob._ I don’t know. I did not care about them, and I made the best of my way home.

_Mr. An._ That would have been right if you had been sent with a message; but as you only walked for amusement, it would have been wiser to have sought out as many sources of it as possible. But so it is—one man walks through the world with his eyes open, and another with them shut; and upon this difference depends all the superiority of knowledge the one acquires above the other. I have known sailors who had been in all the quarters of the world, and could tell you nothing but the signs of the tippling-houses they frequented in different ports, and the price and quality of the liquor. On the other hand, a Franklin could not cross the channel without making some observations useful to mankind. While many a vacant, thoughtless youth is whirled throughout Europe without gaining a single idea worth crossing a street for, the observing eye and inquiring mind find matter of improvement and delight in every ramble in town or country. Do _you_, then, William, continue to make use of your eyes: and _you_, Robert, learn that eyes were given you to use.

[Illustration:

Umbelliferous Plants, p. 252.

EVENING XXI. ]

WHY THE EARTH MOVES ROUND THE SUN.

_Papa_—_Lucy_.

_Papa._ You remember, Lucy, that I explained to you some time ago what was the cause that things fell to the ground.

_Lucy._ O yes; it was because the ground drew them to it.

_Pa._ True. That is a consequence of the universal law in nature, that bodies attract each other in proportion to their bulk. So a very small thing in the neighbourhood of a very large one, always tends to go to it, if not prevented by some or other power. Well—you know I told you that the sun was a ball a vast many times bigger than the ball we inhabit, called the earth; upon which you properly asked, how then it happened that the earth did not fall into the sun.

_Lu._ And why does it not?

_Pa._ That I am going to explain to you. You have seen your brother whirl round an ivory ball tied to the end of a string, which he held in his hand.

_Lu._ Yes; and I have done it myself, too.

_Pa._ Well, then—you felt that the ball was continually pulling, as if it tried to make its escape?

_Lu._ Yes; and one my brother was swinging _did_ make its escape, and flew through the sash.

_Pa._ It did so. That was a lesson, in the _centrifugal_ motion, or that power by which a body thus whirled, continually endeavours to fly off from the centre round which it moves. This is owing to the force or impulse you give it at setting out, as if you were going to throw it away from you. The string by which you hold it, on the contrary, is the power which keeps the ball toward the centre, called the _centripetal_ power. Thus you see there are two powers acting upon the ball at the same time, one to make it fly off, the other to hold it in; and the consequence is, that it moves directly according to neither, but between both; that is, round and round. This it continues to do while you swing it properly; but if the string breaks or slips off, away flies the ball; on the other hand, if you cease to give it the whirling force, it falls toward your hand.

_Lu._ I understand all this.

_Pa._ I will give you another instance of this double force acting at the same time. Do not you remember seeing some curious feats of horsemanship?

_Lu._ Yes.

_Pa._ One of them was, that a man standing with one leg upon the saddle, and riding full speed, threw up balls into the air, and catched them as they fell.

_Lu._ I remember it very well.

_Pa._ Perhaps you would have expected these balls to have fallen behind him, as he was going at such a rate?

_Lu._ So I did.

_Pa._ But you saw that they fell into his hand as directly as if he had been standing quite still. That was because at the instant he threw them up, they received the motion of the horse straight forward as well as the upright motion that he gave them, so that they made a slanting line through the air, and came down in the same place they would have reached if he had held them in his hand all the while.

_Lu._ That is very curious, indeed!

_Pa._ In the same manner you may have observed, in riding in a carriage, that if you throw anything out of the window, it falls directly opposite, just as if the carriage was standing still, and is not left behind you.

_Lu._ I will try that the next time I ride in one.

_Pa._ You are then to imagine the sun to be a mighty mass of matter, many thousand times bigger than our earth, placed in the centre, quiet and unmoved. You are to conceive our earth, as soon as created, launched with vast force in a straight line, as if it were a bowl on a green. It would have flown off in this line for ever, through the boundless regions of space, had it not at the same instant received a pull from the sun by its attraction. By the wonderful skill of the Creator, these two forces were made exactly to counterbalance each other; so that just as much as the earth, from the original motion given to it, tends to fly forward, just so much the sun draws it to the centre; and the consequence is, that it takes a course between the two, which is a circle round and round the sun.

_Lu._ But if the earth was set a rolling like a bowl upon a green, I should think it would stop of itself, as the bowl does.

_Pa._ The bowl stops because it is continually rubbing against the ground, which checks its motion, but the ball of the earth moves in empty space, where there is nothing to stop it.

_Lu._ But if I throw a ball through the air, it will not go on for ever, but it will come down to the ground.

_Pa._ That is because the force with which you can throw it is much less than the force by which it is drawn to the earth. But there is another reason, too, which is the resistance of the air. This space all round us and over us is not empty space; it is quite full of a thin transparent fluid called air.

_Lu._ Is it?

_Pa._ Yes. If you move your hand quickly through it, you will find something resisting you, though in a slight degree. And the wind, you well know, is capable of pressing against anything with almost irresistible force; and yet wind is nothing but a quantity of air put into violent motion. Everything, then, that moves through the air is continually obliged to push some of this fluid out of the way, by which means it is constantly losing part of its motion.

_Lu._ Then the earth would do the same?

_Pa._ No; for it moves in _empty space_.

_Lu._ What, does it not move through the air?

_Pa._ The earth does not move _through_ the air, but carries the air along with it. All the air is contained in what is called the _atmosphere_, which you may compare to a kind of mist or fog clinging all round to the ball of the earth, and reaching a certain distance above it, which has been calculated at above forty-five miles.

_Lu._ That is above the clouds, then.

_Pa._ Yes: all the clouds are within the atmosphere, for they are supported by the air. Well—this atmosphere rolls about along with the earth, as if it were a part of it, and moves with it through the sky, which is a vast field of empty space. In this immense space are all the stars and planets, which have also their several motions. There is nothing to stop them, and therefore they continually go on, by means of the force that the Creator has originally impressed upon them.

_Lu._ Do not some of the stars move round the sun, as well as our earth?

_Pa._ Yes; those that are called _planets_. These are all subject to the same laws of motion with our earth. They are attracted by the sun as their centre, and form, along with the earth, that assemblage of worlds, which is called the _solar system_.

_Lu._ Is the moon one of them?

_Pa._ The moon is called a _secondary_ planet, because its immediate connexion is with our earth, round which it rolls, as we do round the sun. It, however, accompanies our earth on its journey round the sun. But I will tell you more about its motion, and about the other planets and stars another time. It is enough at present, if you thoroughly understand what I have been describing.

_Lu._ I think I do.

THE UMBELLIFEROUS PLANTS.

_Tutor_—_George_—_Harry_.

_Harry._ What plant is that man gathering under the hedge?

_George._ I don’t know; but the boys call the stalks _hexes_, and blow through them.

_Har._ I have seen them; but I want to know the plant.

_Geo._ Will you please to tell us, sir, what it is?

_Tutor._ It is hemlock.

_Geo._ Hemlock is poison is it not?

_Tut._ Yes, in some degree; and it is also a medicine; that man is gathering it for the apothecaries.

_Har._ I should like to know it.

_Tut._ Well then—go and bring one.

[Harry _fetches it_.

_Geo._ I think I have seen a great many of this sort.

_Tut._ Perhaps you may; but there are many other kinds of plants extremely like it. It is one of a large family called the _umbelliferous_, which contains both food, physic, and poison. It will be worth while for you to know something about them, so let us examine this hemlock closely. You see this tall hollow stalk, which divides into several branches, from each of which spring spokes or _rundles_, as they are called, of flower-stalks. You see they are like rays from a circle, or the spokes of a wheel.

_Har._ Or like the sticks of an umbrella.

_Tut._ True; and they are called _umbels_, which has the same derivation. If you pursue one of these rundles or umbels, you will find that each stick or spoke terminates in another set of smaller stalks, each of which bears a single small flower.

_Geo._ They are small ones, indeed!

_Tut._ But if you look sharply, I dare say your eyes are good enough to distinguish that they are divided into five leaves, and furnished with five chives and two pistils in the middle.

_Har._ I can see them.

_Geo._ And so can I.

_Tut._ The pistils are succeeded by a sort of fruit, which is a twin-seed joined in the middle, as you may see in this rundle that is past flowering. Here I divide one of them into two.

_Geo._ Would each of these grow?

_Tut._ Yes. Well, this is the structure of the flowering part of the umbelliferous tribe. Now for the leaf. Pluck one.

_Har._ Is this one leaf, or many?

_Tut._ It is properly one, but it is cut and divided into many portions. From this mid-rib spring smaller leaves set opposite each other; and from the rib of each of these proceed others, which themselves are also divided. These are called doubly or trebly pinnated leaves; and most of the umbelliferous plants, but not all, have leaves of this kind.

_Har._ It is like a parsley-leaf.

_Tut._ True—and parsley is one of the same tribe, and hemlock and others are sometimes mistaken for it.

_Geo._ How curiously the stalk of this hemlock is spotted!

_Tut._ Yes. That is one of the marks by which it is known. It is also distinguished by its peculiar smell, and by other circumstances which you can only understand when you have compared a number of the tribe. I will now tell you about some others, the names of which you are probably acquainted with. In the first place, there are carrots and parsnips.

_Har._ Carrots and parsnips!—they are not poisons, I am sure.

_Geo._ I remember, now, that carrots have such a leaf as this.

_Tut._ They have. It is the _roots_ of these, you know, that are eaten. But we eat the _leaves_ of parsley and fennel, which are of the same class. Celery is another, the _stalks_ of which are chiefly used, made white by trenching up the earth about them. The stalks of angelica are used differently.

_Har._ I know how—candied.

_Tut._ Yes. Then there are many of which the _seeds_ are used. There is caraway.

_Har._ What, the seeds that are put into cakes and comfits?

_Tut._ Yes. They are warm and pungent to the taste; and so are the seeds of many others of the umbelliferous plants, as coriander, fennel, wild carrot, angelica, anise, cummin, and dill. All these are employed in food or medicine, and are good in warming or strengthening the stomach.

_Har._ Those are pleasant medicines enough.

_Tut._ They are; but you will not say the same of some others of the class, which are noted medicines too; such as the plant yielding asafœtida, and several more, from which what are called the fetid gums are produced.

_Geo._ Asafœtida!—that’s nasty stuff, I know; does it grow here?

_Tut._ No; and most of the sweet seeds I before mentioned come from abroad too. Now I will tell you of some of the poisons.

_Har._ Hemlock is one that we know already.

_Tut._ Yes. Then there is another kind that grows in the water, and is more poisonous, called water-hemlock. Another is a large plant growing in ditches, with leaves extremely like celery, called hemlock-dropwort. Another, common in drier situations, and distinguished by leaves less divided than most of the class, is cow-parsnip, or madnep. Of some of these the leaves, of others the root, is most poisonous. Their effects are to make the head giddy, bring on stupidity or delirium, and cause violent sickness. The Athenians used to put criminals to death by making them drink the juice of a kind of hemlock growing in that country, as you may read in the life of that excellent philosopher, Socrates, who was killed in that manner.

_Har._ What was he killed for?

_Tut._ Because he was wiser and better than his fellow-citizens. Among us it is only by accident that mischief is done by these plants. I remember a melancholy instance of a poor boy, who, in rambling about the fields with his little brothers and sisters, chanced to meet with a root of hemlock-dropwort. It looked so white and nice, that he was tempted to eat a good deal of it. The other children also ate some, but not so much. When they got home they were all taken very ill. The eldest boy, who had eaten most, died in great agony. The others recovered, after suffering a great deal.

_Geo._ Is there any way of preventing their bad effects?

_Tut._ The best way is to clear the stomach as soon as possible by a strong vomit and large draughts of warm water. After that, vinegar is useful in removing the disorder of the head.

_Har._ But are the roots sweet and pleasant, that people should be tempted to eat them?

_Tut._ Several of them are. There is a small plant of the tribe, the root of which is much sought after by boys, who dig for it with their knives It is round, and called earth-nut, or pig-nut.

_Geo._ But that’s not poison, I suppose?

_Tut._ No; but it is not very wholesome. I believe, however, that the roots of the most poisonous become innocent by boiling. I have heard that boiled hemlock roots are as good as carrots.

_Geo._ I think I should not like to eat them, however. But pray, why should there be any poisons at all?

_Tut._ What we call poisons, are only hurtful to particular animals. They are the proper food of others, and no doubt do more good than hurt in the creation. Most of the things that are poisonous to us in large quantities, are useful medicines in small ones; and we have reason bestowed upon _us_, to guard us against mischief. Other animals, in general, refuse by instinct what would prove hurtful to them. You see beneath yonder hedge a great crop of tall flourishing plants with white flowers. They are of the umbelliferous family, and are called wild cicely, or cow-weed. The latter name is given them, because the cows will not touch them, though the pasture be ever so bare.

_Har._ Would they poison them?

_Tut._ Perhaps they would: at least they are not proper food for them. We will go and examine them, and I will show you how they differ from hemlock, for which they are sometimes mistaken.

_Geo._ I should like to get some of these plants, and dry them.

_Tut._ You shall, and write down the names of them all, and learn to know the innocent from the hurtful.