Kitabı oku: «Practical Education, Volume II», sayfa 6

CHAPTER XVIII

CHEMISTRY

In the first attempts to teach chemistry to children, objects should be selected, the principal properties of which may be easily discriminated by the senses of touch, taste or smell; and such terms should be employed as do not require accurate definition.

When a child has been caught in a shower of snow, he goes to the fire to warm and dry himself. After he has been before the fire for some time, instead of becoming dry, he finds that he is wetter than he was before: water drops from his hat and clothes, and the snow with which he was covered disappears. If you ask him what has become of the snow, and why he has become wetter, he cannot tell you. Give him a tea-cup of snow, desire him to place it before the fire, he perceives that the snow melts, that it becomes water. If he puts his finger into the water, he finds that it is warmer than snow; he then perceives that the fire which warmed him, warmed likewise the snow, which then became water; or, in other words, he discovers, that the heat which came from the fire goes into the snow and melts it: he thus acquires the idea of the dissolution of snow by heat.

If the cup containing the water, or melted snow, be taken from the fire, and put out of the window on a frosty day, he perceives, that in time the water grows colder; that a thin, brittle skin spreads over it; which grows thicker by degrees, till at length all the water becomes ice; and if the cup be again put before the fire, the ice returns to water. Thus he discovers, that by diminishing the heat of water, it becomes ice; by adding heat to ice, it becomes water.

A child watches the drops of melted sealing-wax as they fall upon paper. When he sees you stir the wax about, and perceives, that what was formerly hard, now becomes soft and very hot, he will apply his former knowledge of the effects of heat upon ice and snow, and he will tell you that the heat of the candle melts the wax. By these means, the principle of the solution of bodies by heat, will be imprinted upon his memory; and you may now enlarge his ideas of solution.

When a lump of sugar is put into a dish of hot tea, a child sees that it becomes less and less, till at last it disappears. What has become of the sugar? Your pupil will say that it is melted by the heat of the tea: but if it be put into cold tea, or cold water, he will find that it dissolves, though more slowly. You should then show him some fine sand, some clay, and chalk, thrown into water; and he will perceive the difference between mechanical mixture and diffusion, or chemical mixture. Chemical mixture, as that of sugar in water, depends upon the attraction that subsists between the parts of the solid and fluid which are combined. Mechanical mixture is only the suspension of the parts of a solid in a fluid. When fine sand, chalk, or clay, are put into water, the water continues for some time turbid or muddy; but by degrees the sand, &c. falls to the bottom, and the water becomes clear. In the chemical mixture of sugar and water, there is no muddiness, the fluid is clear and transparent, even whilst it is stirred, and when it is at rest, there is no sediment, the sugar is joined with the water; a new, fluid substance, is formed out of the two simple bodies sugar and water, and though the parts which compose the mixture are not discernible to the eye, yet they are perceptible by the taste.

After he has observed the mixture, the child should be asked, whether he knows any method by which he can separate the sugar from the water. In the boiling of a kettle of water, he has seen the steam which issues from the mouth of the vessel; he knows that the steam is formed by the heat from the fire, which joining with the water drives its parts further asunder, and makes it take another form, that of vapour or steam. He may apply this knowledge to the separation of the sugar and water; he may turn the water into steam, and the sugar will be left in the vessel in a solid form. If, instead of evaporating the water, the boy had added a greater quantity of sugar to the mixture, he would have seen, that after a certain time, the water would have dissolved no more of the sugar; the superfluous sugar would fall to the bottom of the vessel as the sand had done: the pupil should then be told that the liquid is saturated with the solid.

By these simple experiments, a child may acquire a general knowledge of solution, evaporation, and saturation, without the formality of a lecture, or the apparatus of a chemist. In all your attempts to instruct him in chemistry, the greatest care should be taken that he should completely understand one experiment, before you proceed to another. The common metaphorical expression, that the mind should have time to digest the food which it receives, is founded upon fact and observation.

Our pupil should see the solution of a variety of substances in fluids, as salt in water; marble, chalk, or alkalies, in acids; and camphire in spirits of wine: this last experiment he may try by himself, as it is not dangerous. Certainly many experiments are dangerous, and therefore unfit for children; but others may be selected, which they may safely try without any assistance; and the dangerous experiments may, when they are necessary, be shown to them by some careful person. Their first experiments should be such as they can readily execute, and of which the result may probably be successful: this success will please and interest the pupils, and will encourage them to perseverance.

A child may have some spirit of wine and some camphire given to him; the camphire will dissolve in the spirit of wine, till the spirit is saturated; but then he will be at a loss how to separate them again. To separate them, he must pour into the mixture a considerable quantity of water; he will immediately see the liquor, which was transparent, become muddy and white: this is owing to the separation of the camphire from the spirit; the camphire falls to the bottom of the vessel in the form of a curd. If the child had weighed the camphire, both before and after its solution, he would have found the result nearly the same. He should be informed, that this chemical operation (for technical terms should now be used) is called precipitation: the substance that is separated from the mixture by the introduction of another body, is cast down, or precipitated from the mixture. In this instance, the spirit of wine attracted the camphire, and therefore dissolved it. When the water was poured in, the spirit of wine attracted the water more strongly than it did the camphire; the camphire being let loose, fell to the bottom of the vessel.

The pupil has now been shown two methods, by which a solid may be separated from a fluid in which it has been dissolved.

A still should now be produced, and the pupil should be instructed in the nature of distillation. By experiments he will learn the difference between the volatility of different bodies; or, in other words, he will learn that some are made fluid, or are turned into vapour, by a greater or less degree of heat than others. The degrees of heat should be shown to him by the thermometer, and the use of the thermometer, and its nature, should be explained. As the pupil already knows that most bodies expand by heat, he will readily understand, that an increase of heat extends the mercury in the bulb of the thermometer, which, having no other space for its expansion, rises in the small glass tube; and that the degree of heat to which it is exposed, is marked by the figures on the scale of the instrument.

The business of distillation, is to separate the more volatile from the less volatile of two bodies. The whole mixture is put into a vessel, under which there is fire: the most volatile liquor begins first to turn into vapour, and rises into a higher vessel, which, being kept cold by water or snow, condenses the evaporated fluid; after it has been condensed, it drops into another vessel. In the experiment that the child has just tried, after having separated the camphire from the spirit of wine by precipitation, he may separate the spirit from the water by distillation. When the substance that rises, or that is separated from other bodies by heat, is a solid, or when what is collected after the operation, is solid, the process is not called distillation, but sublimation.

Our pupil may next be made acquainted with the general qualities of acids and alkalies. For instructing him in this part of chemistry, definition should as much as possible be avoided; example, and occular demonstration, should be pursued. Who would begin to explain by words the difference between an acid and an alkali, when these can be shown by experiments upon the substances themselves? The first great difference which is perceptible between an acid and an alkali, is their taste. Let a child have a distinct perception of the difference of their tastes; let him be able to distinguish them when his eyes are shut; let him taste the strongest of each so as not to hurt him, and when he has once acquired distinct notions of the pungent taste of an alkali, and of the sour taste of an acid, he will never forget the difference. He must afterwards see the effects of an acid and alkali on the blue colour of vegetables at separate times, and not on the same day; by these means he will more easily remember the experiments, and he will not confound their different results. The blue colour of vegetables is turned red by acids, and green by alkalies. Let your pupil take a radish, and scrape off the blue part into water; it should be left for some time, until the water becomes of a blue colour: let him pour some of this liquor into two glasses; add vinegar or lemon juice to one of them, and the liquor will become red; dissolve some alkali in water, and pour this into the other glass, and the dissolved radish will become green. If into the red mixture alkali be poured, the colour will change into green; and if into the liquor which was made green, acid be poured, the colour will change to red: thus alternately you may pour acid or alkali, and produce a red or green colour successively. Paper stained with the blue colour of vegetables, is called test paper; this is changed by the least powerful of the acids or alkalies, and will, therefore, be peculiarly useful in the first experiments of our young pupils. A child should for safety use the weakest acids in his first trials, but he should be shown that the effects are similar, whatever acids we employ; only the colour will be darker when we make use of the strong, than when we use the weak acids. By degrees the pupil should be accustomed to employ the strong acids; such as the vitriolic, the nitric, and the muriatic, which three are called fossil acids, to distinguish them from the vegetable, or weaker acids. We may be permitted to advise the young chemist to acquire the habit of wiping the neck of the vessel out of which he pours any strong acid, as the drops of the liquor will not then burn his hand when he takes hold of the bottle; nor will they injure the table upon which he is at work. This custom, trivial as it may seem, is of advantage, as it gives an appearance of order, and of ease, and steadiness, which are all necessary in trying chemical experiments. The little pupil may be told, that the custom which we have just mentioned, is the constant practice of the great chemist, Dr. Black.

We should take care how we first use the term salt in speaking to children, lest they should acquire indistinct ideas: he should be told, that the kind of salt which he eats is not the only salt in the world; he may be put in mind of the kind of salts which he has, perhaps, smelt in smelling-bottles; and he should be further told, that there are a number of earthy, alkaline, and metallic salts, with which he will in time become acquainted.

When an acid is put upon an alkali, or upon limestone, chalk, or marle, a bubbling may be observed, and a noise is heard; a child should be told, that this is called effervescence. After some time the effervescence ceases, and the limestone, &c. is dissolved in the acid. This effervescence, the child should be informed, arises from the escape of a considerable quantity of a particular sort of air, called fixed air, or carbonic acid gas. In the solution of the lime in the acid, the lime and acid have an attraction for one another; but as the present mixture has no attraction for the gas, it escapes, and in rising, forms the bubbling or effervescence. This may be proved to a child, by showing him, that if an acid is poured upon caustic lime (lime which has had this gas taken from it by fire) there will be no effervescence.

There are various other chemical experiments with which children may amuse themselves; they may be employed in analyzing marle, or clays; they may be provided with materials for making ink or soap. It should be pointed out to them, that the common domestic and culinary operations of making butter and cheese, baking, brewing, &c. are all chemical processes. We hope the reader will not imagine, that we have in this slight sketch pretended to point out the best experiments which can be devised for children; we have only offered a few of the simplest which occurred to us, that parents may not, at the conclusion of this chapter, exclaim, "What is to be done? How are we to begin? What experiments are suited to children? If we knew, our children should try them."

It is of little consequence what particular experiment is selected for the first; we only wish to show, that the minds of children may be turned to this subject; and that, by accustoming them to observation, we give them not only the power of learning what has been already discovered, but of adding, as they grow older, something to the general stock of human knowledge.

CHAPTER XIX

ON PUBLIC AND PRIVATE EDUCATION

The anxious parent, after what has been said concerning tasks and classical literature, will inquire whether the whole plan of education recommended in the following pages, is intended to relate to public or to private education. It is intended to relate to both. It is not usual to send children to school before they are eight or nine years old: our first object is to show how education may be conducted to that age in such a manner, that children may be well prepared for the acquisition of all the knowledge usually taught at schools, and may be perfectly free from many of the faults that pupils sometimes have acquired before they are sent to any public seminary. It is obvious, that public preceptors would be saved much useless labour and anxiety, were parents to take some pains in the previous instruction of their children; and more especially, if they were to prevent them from learning a taste for total idleness, or habits of obstinacy and of falsehood, which can scarcely be conquered by the utmost care and vigilance. We can assure parents, from experience, that if they pursue steadily a proper plan with regard to the understanding and the moral habits, they will not have much trouble with the education of their children after the age we have mentioned, as long as they continue to instruct them at home; and if they send them to public schools, their superiority in intellect and in conduct will quickly appear. Though we have been principally attentive to all the circumstances which can be essential to the management of young people during the first nine or ten years of their lives, we have by no means confined our observations to this period alone; but we have endeavoured to lay before parents a general view of the human mind (as far as it relates to our subject) of proper methods of teaching, and of the objects of rational instruction – so that they may extend the principles which we have laid down, through all the succeeding periods of education, and may apply them as it may best suit their peculiar situations, or their peculiar wishes. We are fully conscious, that we have executed but very imperfectly even our own design; that experimental education is yet but in its infancy, and that boundless space for improvement remains; but we flatter ourselves, that attentive parents and preceptors will consider with candour the practical assistance which is offered to them, especially as we have endeavoured to express our opinions without dogmatical presumption, and without the illiberal exclusion of any existing institutions or prevailing systems. People who, even with the best intentions, attack with violence any of these, and who do not consider what is practicable, as well as what ought to be done, are not likely to persuade, or to convince mankind to increase the general sum of happiness, or their own portion of felicity. Those who really desire to be of service to society, should point out decidedly, but with temperate indulgence for the feelings and opinions of others, whatever appears to them absurd or reprehensible in any prevailing customs: having done this, they will rest in the persuasion that what is most reasonable, will ultimately prevail.

Mankind, at least the prudent and rational part of mankind, have an aversion to pull down, till they have a moral certainty that they can build up a better edifice than that which has been destroyed. Would you, says an eminent writer, convince me, that the house I live in is a bad one, and would you persuade me to quit it; build a better in my neighbourhood; I shall be very ready to go into it, and shall return you my very sincere thanks. Till another house be ready, a wise man will stay in his old one, however inconvenient its arrangement, however seducing the plans of the enthusiastic projector. We do not set up for projectors, or reformers: we wish to keep steadily in view the actual state of things, as well as our own hopes of progressive improvement; and to seize and combine all that can be immediately serviceable: all that can assist, without precipitating improvements. Every well informed parent, and every liberal school-master, must be sensible, that there are many circumstances in the management of public education which might be condemned with reason; that too much time is sacrificed to the study of the learned languages; that too little attention is paid to the general improvement of the understanding and formation of the moral character; that a school-master cannot pay attention to the temper or habits of each of his numerous scholars; and that parents, during that portion of the year which their children spend with them, are not sufficiently solicitous to co-operate with the views of the school-master; so that the public is counteracted by the private education. These, and many other things, we have heard objected to schools; but what are we to put in the place of schools? How are vast numbers who are occupied themselves in public or professional pursuits, how are men in business or in trade, artists or manufacturers, to educate their families, when they have not time to attend to them; when they may not think themselves perfectly prepared to undertake the classical instruction and entire education of several boys; and when, perhaps, they may not be in circumstances to engage the assistance of such a preceptor as they could approve? It is obvious, that if in such situations parents were to attempt to educate their children at home, they would harass themselves, and probably spoil their pupils irrecoverably. It would, therefore, be in every respect impolitic and cruel to disgust those with public schools, who have no other resource for the education of their families. There is another reason which has perhaps operated upon many in the middle ranks of life unperceived, and which determines them in favour of public education. Persons of narrow fortune, or persons who have acquired wealth in business, are often desirous of breeding up their sons to the liberal professions: and they are conscious that the company, the language, and the style of life, which their children would be accustomed to at home, are beneath what would be suited to their future professions. Public schools efface this rusticity, and correct the faults of provincial dialect: in this point of view they are highly advantageous. We strongly recommend it to such parents to send their children to large public schools, to Rugby, Eton, or Westminster; not to any small school; much less to one in their own neighbourhood. Small schools are apt to be filled with persons of nearly the same stations, and out of the same neighbourhood: from this circumstance, they contribute to perpetuate uncouth antiquated idioms, and many of those obscure prejudices which cloud the intellect in the future business of life.

Whilst we admit the necessity which compels the largest portion of society to prefer public seminaries of education, it is incumbent upon us to caution parents from expecting that the moral character, the understandings, or the tempers of their children, should be improved at large schools; there the learned languages, we acknowledge, are successfully taught. Many satisfy themselves with the assertion, that public education is the least troublesome, that a boy once sent to school is settled for several years of life, and will require only short returns of parental care twice a year at the holydays. It is hardly to be supposed, that those who think in this manner, should have paid any anxious, or at least any judicious attention to the education of their children, previously to sending them to school. It is not likely that they should be very solicitous about the commencement of an education which they never meant to finish: they would think, that what could be done during the first few years of life, is of little consequence; that children from four to seven years old are too young to be taught; and that a school would speedily supply all deficiencies, and correct all those faults which begin at that age to be troublesome at home. Thus to a public school, as to a general infirmary for mental disease, all desperate subjects are sent, as the last resource. They take with them the contagion of their vices, which quickly runs through the whole tribe of their companions, especially amongst those who happen to be nearly of their own age, whose sympathy peculiarly exposes them to the danger of infection. We are often told, that as young people have the strongest sympathy with each other, they will learn most effectually from each other's example. They do learn quickly from example, and this is one of the dangers of a public school: a danger which is not necessary, but incidental; a danger against which no school-master can possibly guard, but which parents can, by the previous education of the pupils, prevent. Boys are led, driven, or carried to school; and in a school-room they first meet with those who are to be their fellow prisoners. They do not come with fresh unprejudiced minds to commence their course of social education; they bring with them all the ideas and habits which they have already learned at their respective homes. It is highly unreasonable to expect, that all these habits should be reformed by a public preceptor. If he had patience, how could he have time for such an undertaking? Those who have never attempted to break a pupil of any one bad habit, have no idea of the degree of patience requisite to success. We once heard an officer of dragoons assert, that he would rather break twenty horses of their bad habits, than one man of his. The proportionate difficulty of teaching boys, may be easily calculated.

It is sometimes asserted, that the novelty of a school life, the change of situation, alters the habits, and forms in boys a new character. Habits of eight or nine years standing, cannot be instantaneously, perhaps can never be radically, destroyed; they will mix themselves imperceptibly with the new ideas which are planted in their minds, and though these may strike the eye by the rapidity of their growth, the others, which have taken a strong root, will not easily be dispossessed of the soil. In this new character, as it is called, there will, to a discerning eye, appear a strong mixture of the old disposition. The boy, who at home lived with his father's servants, and was never taught to have any species of literature, will not acquire a taste for it at school, merely by being compelled to learn his lessons; the boy, who at home was suffered to be the little tyrant of a family, will, it is true, be forced to submit to superior strength or superior numbers at school;²⁹ but does it improve the temper to practise alternately the habits of a tyrant and a slave? The lesson which experience usually teaches to the temper of a school-boy, is, that strength, and power, and cunning, will inevitably govern in society: as to reason, it is out of the question, it would be hissed or laughed out of the company. With respect to social virtues, they are commonly amongst school-boys so much mixed with party spirit, that they mislead even the best dispositions. A boy at home, whose pleasures are all immediately connected with the idea of self, will not feel a sudden enlargement of mind from entering a public school. He will, probably, preserve his selfish character in his new society; or, even suppose he catches that of his companions, the progress is not great in moral education from selfishness to spirit of party: the one is a despicable, the other a dangerous, principle of action. It has been observed, that what we are when we are twenty, depends on what we were when we were ten years old. What a young man is at college, depends upon what he was at school; and what he is at school, depends upon what he was before he went to school. In his father's house, the first important lessons, those which decide his future abilities and character, must be learned. We have repeated this idea, and placed it in different points of view, in hopes that it will catch and fix the attention. Suppose that parents educated their children well for the first eight or nine years of their lives, and then sent them all to public seminaries, what a difference this must immediately make in public education: the boys would be disposed to improve themselves with all the ardour which the most sanguine preceptor would desire; their tutors would find that there was nothing to be unlearned; no habits of idleness to conquer; no perverse stupidity would provoke them; no capricious contempt of application would appear in pupils of the quickest abilities. The moral education could then be made a part of the preceptor's care, with some hopes of success; the pupils would all have learned the first necessary moral principles and habits; they would, consequently, be all fit companions for each other; in each other's society they would continue to be governed by the same ideas of right and wrong by which they had been governed all their lives; they would not have any new character to learn; they would improve, by mixing with numbers, in the social virtues, without learning party spirit; and though they would love their companions, they would not, therefore, combine together to treat their instructers as pedagogues and tyrants. This may be thought an Utopian idea of a school; indeed it is very improbable, that out of the numbers of parents who send their children to large schools, many should suddenly be much moved, by any thing that we can say, to persuade them to take serious trouble in their previous instruction. But much may be effected by gradual attempts. Ten well educated boys, sent to a public seminary at nine or ten years old, would, probably, far surpass their competitors in every respect; they would inspire others with so much emulation, would do their parents and preceptors so much credit, that numbers would eagerly inquire into the causes of their superiority; and these boys would, perhaps, do more good by their example, than by their actual acquirements. We do not mean to promise, that a boy judiciously educated, shall appear at ten years old a prodigy of learning; far from it: we should not even estimate his capacity, or the chain of his future progress, by the quantity of knowledge stored in his memory, by the number of Latin lines he had got by rote, by his expertness in repeating the rules of his grammar, by his pointing out a number of places readily in a map, or even by his knowing the latitude and longitude of all the capital cities in Europe; these are all useful articles of knowledge: but they are not the test of a good education. We should rather, if we were to examine a boy of ten years old, for the credit of his parents, produce proofs of his being able to reason accurately, of his quickness in invention, of his habits of industry and application, of his having learned to generalize his ideas, and to apply his observations and his principles: if we found that he had learned all, or any of these things, we should be in little pain about grammar, or geography, or even Latin; we should be tolerably certain that he would not long remain deficient in any of these; we should know that he would overtake and surpass a competitor who had only been technically taught, as certainly as that the giant would overtake the panting dwarf, who might have many miles the start of him in the race. We do not mean to say, that a boy should not be taught the principles of grammar, and some knowledge of geography, at the same time that his understanding is cultivated in the most enlarged manner: these objects are not incompatible, and we particularly recommend it to parents who intend to send their children to school, early to give them confidence in themselves, by securing the rudiments of literary education; otherwise their pupils, with a real superiority of understanding, may feel depressed, and may, perhaps, be despised, when they mix at a public school with numbers who will estimate their abilities merely by their proficiency in particular studies.