many joints; as are also those of the sugar-cane, and the bamboo, of which fishing-rods and walking-sticks are often made. Some of these are very tall plants; but the seeds of them are small in proportion, and not useful for food. But there is yet another kind of grass-like plants common among us.

G. What is that?

T. Have you not observed in the marshes, and on the sides of ditches, a coarse, broader-leaved sort of grass, with large dark-coloured spikes? This is sedge, in Latin carex; and there are many sorts of it. H. What is that good for?

T. It is eaten by cattle, both fresh and dry; but is inferior in quality to good grass.

G. What is it that makes one kind of grass better than another ?

T. There are various properties which give value to grasses. Some spread more than others, resist frost and drought better; yield a greater crop of leaves, and are therefore better for pasturage and hay. The juices of some are more nourishing and sweet than those of others. In general, however, different grasses are suited to different soils; and by improving soils, the quality of the grass is improved.

G. Does grass grow in all countries ?

T. Yes the green turf, which naturally covers fertile soils of all countries, is composed chiefly of grasses of various kinds. They form, therefore, the verdant carpet extended over the earth; and, humble as they are, they contribute more to beauty and utility, than any other part of the vegetable creation.

H. What more than trees?

T. Yes, certainly. A land entirely covered with trees would be gloomy, unwholesome, and scarcely inhabitable; whereas the meadow, the down, and the corn-field, afford the most agreeable prospects to the eye, and furnish every necessary, and many of the luxuries of life. Give us corn and grass, and what shall we want for food?

H. Let me see

-what should we have? There are

bread, and flour for puddings.

G. Ay, and milk; for you know cows live on grass and hay so there are cheese and butter, and ali things that are made of milk.

T. And are there not all kinds of meat too, and poultry? And then for drink, there are beer and ale, which are made from barley. For all these we are chiefly indebted to the grasses.

G. Then I am sure we are very much obliged to the grasses.

T. Well-let us now walk homewards. Some time hence, you shall make a collection of all the kinds of grasses, and learn to know them from each other.

A TEA LECTURE.

Tutor-Pupil.

Tut. COME-the tea is ready. Lay by your book, and let us talk a little-You have assisted in teamaking a great many times, and yet I dare say you never considered what sort of an operation it was. Pup. An operation of cookery-is it not?

Tut. You may call it so; but it is properly an operation of chemistry.

Pup. Of chemistry! I thought that had been a very deep sort of a business.

Tut. O-there are many things in common life that belong to the deepest of sciences. Making tea is the chemical operation called infusion, which is, when a hot liquor is poured upon a substance, in order to extract something from it. The water, you see, extracts from the tea-leaves their colour, taste, and flavour.

Pup. Would not cold water do the same?

Tut. It would, but more slowly. Heat assists almost all liquors in their power of extracting the virtues of herbs and other substances. Thus good housewives formerly used to boil their tea, in order to

get all the goodness from it as completely as possible. The greater heat and agitation of boiling make it act more powerfully. The liquor in which a substance has been boiled is called a decoction of that substance. Pup. Then we had a decoction of mutton at dinner to-day?

Tut. We had;-broth is a decoction, and so are gruel and barley-water. But when anything is put to steep in a cold liquor, it is called maceration. The ingredients of which ink is made are macerated. In all these cases, you see, the whole substance does not mix with the liquor, but only part of it. The reason is, that part of it is soluble in the liquor, and part not. Pup. What is the meaning of that ?

Tut. Solution is when a solid put into a fluid entirely disappears in it, leaving the liquor clear. Thus, when I throw this lump of sugar into my tea, you see it gradually wastes away till it is all gone, and then I can taste it in every single drop of my tea; but the tea is as clear as before.

Pup. Salt would do the same.

Tut. It would. But if I were to throw in a lump of chalk, it would lie undissolved at the bottom.

Pup. But it would make the water white.

Tut. True, while it was stirred; and then it would be a diffusion. But while the chalk was thus mixed with the liquor, the latter would lose its transparency, and not recover it again, till, by standing, the chalk had all subsided, and left the liquor as it was before. Pup. How is the cream mixed with the tea?

Tut. Why, that is only diffused, for it takes away the transparency of the tea. But the particles of cream being finer and lighter than those of chalk, it remains longer united with the liquor. However, in time, the cream would separate too, and rise to the top, leaving the tea clear. Now, suppose you had a mixture of sugar, salt, chalk, and tea-leaves, and were to throw it into water, either hot or cold;-what would be the effect?

Pup. The sugar and salt would be dissolved and disappear. The tea-leaves would yield their colour and taste. The chalk-I do not know what would

become of that.

Tut. Why, if the mixture were stirred, the chalk would be diffused through it, and make it turbid, or muddy; but, on standing, it would leave it unchanged. Pup. Then there would remain at bottom the chalk and tea-leaves.

Tut. Yes. The clear liquor would contain in solution salt, sugar, and those particles of the tea, in which its colour and taste consisted: the remainder of the tea and the chalk would lie undissolved.

Pup. Then I suppose tea-leaves, after the tea is made, are lighter than at first.

Tut. Undoubtedly. If taken out and dried, they would be found to have lost part of their weight, and the water would have gained it. Sometimes, however, it is an extremely small portion of a substance which is soluble, but it is that in which its most remarkable qualities reside. Thus, a small piece of spice will communicate a strong flavour to a large quantity of liquid, with very little loss of weight.

Pup. Will all liquors dissolve the same things?

Tut. By no means. Many dissolve in water, that will not in spirit of wine; and the contrary. And upon this difference many curious matters in the arts are founded. Thus spirit varnish is made of a solution of various gums or resins in spirits that will not dissolve in water. Therefore, when it has been laid over any surface with brush, and has become dry, the

This is

rain or moisture of the air will not affect it. the case with the beautiful varnish laid upon coaches. On the other hand, the varnish left by gum-water could not be washed off by spirits.

Pup. I remember when I made gum-water, upon setting the cup in a warm place, it all dried away, and left the gum just as it was before. Would the same happen if I had sugar or salt dissolved in water?

Tut. Yes-upon exposing the solution to warmth, it would dry away, and you would get back your salt and sugar in a solid state, as before.

Pup. But if I were to do so with a cup of tea, what should I get?

Tut. Not tea-leaves, certainly! But your question requires a little previous explanation. It is the property of heat to make most things fly off in vapour, which is called evaporation, or exhalation. But this it does in very different degrees to different substances. Some are very easily made to evaporate; others very difficultly; and others not at all, by the most violent fire we can raise. Fluids in general are easily evaporable; but not equally so. Spirit of wine flies off in vapour much sooner than water; so that if you had a mixture of the two, by applying a gentle heat, you might drive off all the spirit, and leave the water pure. Water, again, is more evaporable than oil. Some solid substances are much disposed to evaporate. Thus, smelling-salts, by a little heat, may entirely be driven away in the air. But, in general, solids are more fixed than fluids; and therefore, when a solid is dissolved in a fluid, it may commonly be recovered again by evaporation. By this operation, common salt is got from sea-water and salt springs, both artificially, and in hot countries, by the natural heat of the sun. When the water is no more than is just sufficient to dissolve the salt, it is called a saturated solution; and on evaporating the water further, the salt begins to separate, forming little regular masses, called crystals. Sugar may be made in like manner to form crystals; and then it is sugar-candy.

Pup. But what is a syrup?

Tut. That is, when so much sugar is dissolved as sensibly to thicken the liquor, but not to separate from it. Well-now to your question about tea. On exposing it to considerable heat, those fine particles in which its flavour consists, being as volatile or evaporable as the water, would fly off along with it; and,