Bat we will not be like these, we will open our eyes, and ask, " What are these forces or fciiries, and how can we see them } "

Just go out into the country, and sit down quietly and watch nature at work. Listen to the wind as it blows, look at the clouds roiling overhead, and the waves rippling on the pond at your feet. Hearken to the brook as it flows by, watch the flower-buds opening one by one, and then ask yourself, How all this is done 'i " Go out in the evening and see the dew gather drop by drop upon the grass, or trace the delicate hoar-frost crystals which bespangle every blade on a winters morning. Look at the •vivid flashes of lightning in a storm, and listen to the pealing thunder: and then tell me, by what machinery is all this wonderful work done } Man does none of it, neither could he stop it if he were to try ; for it is all the work of those invisible forces or fairies whose acquaintance I wish you to make. Day and night, summer and winter, storm or calm, these fairies are at w^ork, and we may hear them and know them, and make friends of them if w^e will.

There is only one gift we must have before we can learn l:o know them —we must have iiuaginatioii. I d ) not mean mere fancy, which creates unreal images and impossible monsters, but imagination, the power of making pictures or images in our mind, of that which is, though it is invisible to us. Most children have this glorious gift, and love to picture to themselves all that is told them, and to hear the same tale over and over again till they see every bit of it as -f it were real. This is why they are sure to love science if its tales are told them aright ; and I, for one, hope the day may never come when we may lose that childish clearness of vision, which enables us through the temporal things which are seen, to realize those eternal truths which are unseen.

If you have this gift of imagination come with me, and in these lectures we will look for the invisible fairies of nature.

Watch a shower of rain. Where do the drops come from } and why are they round, or rather slightly oval ? In our fourth lecture we shall see that the little particles of water of which the rain- drops are made, were held apart and invisible in the air by heat, one of the most wonderful of our forces* or fairies, till the cold wind passed by and chilled the air. Then, when there was no longer so much heat, another invisible force, coliesion^ which is always ready and waiting, seized on the tiny particles at once, and locked them together in a drop, the closest form in which they could lie. Then as the drops became larger and larger they fell into the grasp of another invisible force, gravitation, which dragged them down to the earth, drop by drop, till they made a shower of

I am quite aware of the danger incurred by using this word " force,* especially in the plural ; and how even the most modest little book may suffer at the hands of scientific purists by employing it rashly. As, however, the better term "energy** would not serve here, I hope 1 may be forgiven for retaining the much-abused term, especially as 1 sin la Tery good company.

rain. Pause for a moment and think. You have surely heard of gravitation, by which the sun holds the earth and the planets, and keeps them moving round him in regular order ? Well, it is this same gravitation which is at work also whenever a shower of rain falls to the earth. Who can say that he is not a great invisible giant, always silently and invisibly toiling in great things and small whether we wake or sleep

Now the shower is over, the sun comes out, and the ground is soon as dry as though no rain had fallen. Tell me, what has become of the rain-drops ? Part no doubt have sunk into the ground, and as for the rest, why you will say the sun has dried them up. Yes, but how ? The sun is more than ninety-one millions of miles away ; how has he touched the rain-drops ? Have you ever heard that invisible waves are travelling every second over the space between the sun and us } We shall see in the next lecture how these waves are the sun's messengers to the earth, and how they tear asunder the rain-drops on the ground, scattering them in tiny particles too small for us to see, and bearing them away to the clouds. Here are more invisible fairies working every moment around you, and you cannot even look out of the window witliout seeing the work they are doing.

If, however, the day is cold and frosty, the water dees not fall in a shower of rain ; it comes down in the shape of noiseless snow. Go out after such a snowshower, on a calm day, and look at some of the flakes which have fallen ; you will see, if you choose good specimens, that they are not mere masses of frozen 2 water, but that each one is beautiful six-pointed crystal star. How have these crystals been built up ? What power has been at work arranging their delicate forms ? In the fourth lecture we shall see that up in the clouds another of our invisible fairies, which, for want of a better name, we call the force of crystallization," has caught hold of the tiny particles of water before " cohesion had made them into round drops, and there silently but rapidly, has. moulded them into those delicate crystal stars known as " snowflakes."

And now, suppose that this snow-shower has fallen early in February ; turn aside for a moment from examining the flakes, and clear the newly-fallen snow from off" the flower-bed on the lawn. What is this little green tip peeping up out of the ground under the snowy covering ? It is a young snowdrop plant. Can you tell me why it grows } where it finds its food? what makes it spread out its leaves and add to its stalk day by day ? What fairies are at work here ?

First there is the hidden fairy " life," and of her even our wisest men know but little. But they know something of her way of working, and in Lecture VII. we shall learn how the invisible fairy sunbeams have been busy here also ; how last year's snowdrop plant caught them and stored them up in its bulb, and how now in the spring, as soon as warmth and moisture creep down into the earth, these little imprisoned sunwaves begin to be active, stirring up the matter in the bulb, and making it swell and burst upwards till it sends out a little shoot through the surface of the soil. Then the sun-waves above-ground take up the work, and form green granules in the tiny leaves, helping them to take food out of the air, while the little rootlets below are drinking water out of the ground. The invisible life and invisible sunbeams are busy here, setting actively to work another fairy, the force of "chemical attraction," and so the little snowdrop plant grows and blossoms, without any help from you or me.

One picture more, and then I hope you will believe in my fairies. From the cold garden, you run into the house, and find the fire laid indeed in the grate, but the wood dead and the coals black, waiting to be lighted. You strike a match, and soon there is a blazing fire. Where does the heat come from } Why do the coals burn and give out a glowing light ? Have you not read of gnomes buried down deep in the earth, in mines, and held fast there till some fairy wand has released them, and allowed them to come to earth again ? Well, thousands and millions of years ago, those coals were plants ; and, like the snowdrop in the garden of to-day, they caught the sunbeams and worked them into their leaves. Then the plants died and were buried deep in the earth and the sunbeams with them ; and like the gnomes they lay imprisoned till the coals were dug out by the miners, and brought to your grate ; and just now you yourself took hold of the fairy wand which was to release them. You struck a match, and its atoms clashing with atoms of oxygen in the air, set the invisible fairies " heat " and ** chemical attraction " to work, and they were soon busy within the wood and the coals causing their atoms too to clash ; and the sunbeams, so long imprisoned, leapt into flame. Then you spread out youf hands and cried, Oh, how nice and warm ! " and little thought that ycu were warming yourself with the sunbeams of ages and ages ago.

This is no fancy tale ; it is literally true, as we shall see in Lecture VIII., that the warmth of a coal fire could not exist if the plants of long ago had not used the sunbeams to make their leaves, holding them ready to give up their warmth again whenever those crushed leaves are consumed.

Now, do you believe in, and care for, my fairy-land } Can you see in your imagination fairy Cohesion ever ready to lock atoms together when they draw very near to each other : or fairy Gravitation dragging rain-drops down to the earth : or the fairy of Crystallization building up the snow-flakes in the clouds } Can you picture tiny sunbeam-waves of light and heat travelling from the sun to the earth ? Do you care to know how another strange fairy, * Electricity^ flings the lightning across the sky and causes the rumbling thunder ? Would you like to learn how the sun makes pictures of the world on which he shines, so that w^e can carry about with us photographs or sun-pictures of all the beautiful scenery of the earth ? And have you any curiosity about * Chemical action^ which works such wonders in air, and land, and sea } If you have any wish to know and make friends of these invisible forces, the next question is

How are you to enter the fairy-land rf science ?

There is but one way. Like the knight or peasant in the fairy tales, you must open your eyes. There is no lack of objects, everything around you will tell some history if touched with the fairy wand of imagination. I have often thought, w^hen seeing some sickly child drawn along the street, lying on its back while other children romp and play, how much happiness might be given to sick children at home or in hospitals, if only they were told the stories which lie hidden in the things around them. They need not even move from their beds, for sunbeams can fall on them there, and in a sunbeam there are stories enough to occupy a month. The fire in the grate, the lamp by the bedside, the water in the tumbler, the fly on the ceiling above, the flower in the vase on the table, anything, everything, has its history, and can reveal to us nature's invisible fairies.

Only you must wish to see them. If you go through the world looking upon everything only as so much to eat, to drink, and to use, you will never see the fairies of science. But if you ask yourself why things happen, and how the great God above us has made and governs this world of ours ; if you listen to the wind, and care to learn why it blows ; if you ask the little flower why it opens in the sunshine and closes in the storm ; and if when you find questions you cannot answer, you will take the trouble to hunt out in books, or make experiments, to solve your own questions, then you will learn to knov/ and love those fairies.

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