(a) Does the mud begin to settle while the water is in motion; that is, while it is being shaken?

(b) As soon as it is quiet, does the settling process begin?

(c) Which settles first-the pebbles, the sand or the mud? Which settles on top-that is, which settles last?

(d) Notice that as long as the water is in the least roily, it means that the soil in it has not all settled; if the water is disturbed even a little it becomes roily again, which means that as soon as the water is in motion it takes up its load.

Observations-1. Where is the current swiftest, in the middle or at the side of the stream?

2. What is the difference, in the bottom of the brook, between the place below the swift current and the edges? That is, if you were wading in the brook, where would it be more comfortable for your feet-at the sides or in the swiftest part of the current? Why?

3. Does the brook have a more stony bed where it flows down a hillside than where flowing through a level place?

4. Place a dam across your brook where the bottom is stony, and note how soon it will have a soft mud bottom. Why is this?

5. Can you find a still pool in your brook that has not a soft, muddy bottom? Why is this?

6. Does the brook flow more swiftly in the steep and narrow places than in the wide portions and where it is dammed?

7. Do you think if water, flowing swiftly and carrying a load of mud, were to come to a wider or more level place, like a pool or millpond dam, that it would drop some of its load? Why?

8. If the water flows less swiftly along the edges than in the middle, would this make the bottom below softer and more comfortable to the feet than where the current is swiftest? If so, why?

9. If you can see the place where a brook empties into a pond or lake, how does it make the waters of the latter look after a storm? What is the water of the brook doing to give this appearance, and why?

IO. What becomes of the soil dropped by the brook as it enters a pond or lake? Do you know of any points of land extending out into a lake or pond where the stream enters it? What is a stream delta?

"In the bottom of the valley is a brook that saunters between oozing banks. It falls over stones and dips under fences. It marks an open place on the face of the earth, and the trees and soft herbs bend their branches into the sunlight. The hangbird swings her nest over it. Mossy logs are crumbling into it. There are still pools where the minnows play. The brook runs away and away into the forest. As a boy I explored it but never found its source. came somewhere from the Beyond and its name was Mystery.

It

The mystery of this brook was its changing moods. It had its own way of recording the passing of the weeks and months. I remember never to have seen it twice in the same mood, nor to have got the same lesson from it on two successive days: yet,with all its variety, it always left that same feeling of mystery and that same vague longing to follow to its source and to know the great world that I was sure must lie beyond. I felt that the brook was greater and wiser than I. It became my teacher. I wondered how it knew when March came, and why its round of life recurred so regularly with the returning seasons. I remember that I was anxious for the spring to come, that I might see it again. I longed for the earthy smell when the snow settled away and left bare brown margins along its banks. I watched for the suckers that came up from the river to spawn. I made a note when the first frog peeped. I waited for the unfolding spray to soften the bare trunks. I watched the greening of the banks and looked eagerly for the bluebird when I heard his curling note somewhere high in the air." -"The Nature-Study Idea," L. H. BAILEY

CRYSTAL GROWTH

Teacher's Story

To watch the growth of a crystal is to witness a miracle; involuntarily we stand in awe before it, as a proof that of all truths mathematics is the most divine and inherent in the universe. The teacher will fail to make the best use of this lesson if she does not reveal to the child through it something of the marvel of crystal growth.

A snow crystal. Photomicrograph by W. A.

Bentley.

That a substance which has been dissolved in water should, when the water evaporates, assemble its particles in solid form of a certain shape, with its plane surfaces set exactly at certain angles one to another, always the same whether the crystal be large or small, is quite beyond our understanding Perhaps it is no more miraculous than the growth of living beings, but it seems so. The fact that when an imperfect crystal, unfinished or broken, is placed in water which is saturated with the same substance, it will be built out and made perfect, shows a law of growth so exquisitely exemplified as to again make us glad to be a part of a universe so perfectly governed. Moreover, when crystals show a variation in numbers of angles and planes it is merely a matter of division or multiplication. A snow crystal is a six-rayed star, yet sometimes it has three rays.

The window-sill of a schoolroom may be a place for the working of greater wonders than those claimed by the astrologists of old, when they transmuted baser metals to gold and worthless stones to diamonds. It may be a place where strings of gems are made before the wondering eyes of the children; gems fit to make necklaces for any naiad of the brook or oread of the caves.

It adds much to the interest of this lesson if different colored substances are used for the forming of the crystals. Blue vitriol, potassium bichromate, and alum give beautiful crystals, contrasting in shape as well as in colors.

Copper sulphate and blue vitriol are two names for one substance; it is a poison when taken internally and, therefore, it is best for the teacher to carry on the experiment before the pupils instead of trusting the substance to them indiscriminately. Blue vitriol forms an exquisitely beautiful blue crystal, which is lozenge-shaped with oblique edges. Often, as purchased from the drug store, we find it in the form of rather large, broken, or imperfect crystals. One of the pretty experiments is to place some of these broken crystals in a saucer containing a saturated solution of the vitriol, and note that they straightway assert crystal nature by building out the broken places, and growing into perfect crystals. Blue vitriol is used much in the dying and in the printing of cotton and linen cloths. It has quite wonderful preservative qualities; if either animal or vegetable tissues are permeated by it they will remain dry and unchanged.

Potassium bichromate is also a poison and, therefore, the teacher should make the solution in the presence of the class. It forms orange-red crystals, more or less needle-shaped. It crystallizes so readily that if one drop of the so'ution be placed on a saucer the pupils may see the formation of the crystals by watching it for a few moments through a lens.

The common alum we buy in crystal form, however, it is very much broken. Its crystals are eight-sided and pretty. Alum is widely used in dyes, in medicines, and in many other ways. It is very astringent, as every child knows who has tried to eat it, and has found the lips and tongue much puckered thereby

Although we are more familiar with crystals formed from substances dissolved in water, yet there are some minerals, like iron which crystallize only when they are melted by heat; and there are other crystals, like the snow, which are formed from vapor. Thus, substances must be molten hot, or dissolved in a liquid, or in form of gas, in order to grow into crystals.

LESSON CCXI

CRYSTAL GROWTH

Leading thought-Different substances when dissolved in water will re-form as crystals; each substance forms crystals of its own peculiar color and shape.

Method-Take three test tubes, long vials or clear bottles. Fill one with a solution made by dissolving one part of blue vitriol in three parts of water; fill another by dissolving one part of bichromate of potash with twenty-five parts of water; fill another with one part of alum in three parts of water. Suspend from the mouth of each test tube or vial, a piece of white twine, the upper end tied to a tooth pick, which is placed across the mouth of the vial; the other end should reach the bottom of the vial. If necessary, tie a pebble to the lower end so that it will hang straight. Place the bottles on the window sill of the schoolroom, where the children may observe what is happening. Allow them to stand for a time, until the string in each case is encrusted with crystals; then pull out the string and the crystals. Dry them with a blotter, and let the children observe them closely. Care should be taken to prevent the children from trying to eat these beautiful crystals, by telling them that the red and blue crystals are poisonous.

Observations-1. In which bottle did the crystals form first? Which string is the heaviest with the crystals?

2. What was the color of the water in which the blue vitriol was dissolved? Is it as brilliant in color now as it was when it was first made? Do you think that the growth of the crystals took away from the blue material of the water? Look at the blue vitriol crystals with a lens, and describe their shape. Are the shapes of the large crystals of the vitriol the same as those of the small ones?

3. What is the shape of the crystals of the potassium bichromate? What is the color? Are these crystals as large as those of the blue vitriol or of the alum?

4.

What shapes do you find among the crystals of alum?

5. Do you think that vitriol and potassium bichromate and alum will, under favorable circumstances, always form each its own shape of crystal wherever it occurs in the world? Do you think crystals could be formed without the aid of water?

How many kinds of crystals do you know? What is rock candy? Do you think you could make a string of rock candy if you dissolved sugar in water and placed a string in it?

SALT

Teacher's Story

A "saturated solution" is an uninspiring term to one not chemically trained; and yet it merely means water which holds as much as it can take of the dissolved substance; if the water is hot, it dissolves more of most substances. To make a saturated solution of salt we need two parts of salt or a little more, for good measure, to five parts of water; the water should be stirred until it will take up no more salt.

Form of a salt crystal.

A slip of paper placed in a saucer of this solution will prove a resting place for the crystals as they form. In about two days the miracle will be working, and the pupils should now and then observe its progress. Those saucers set in a draft or in a warm place will show crystals sooner than others, but the crystals will be smaller; for the faster a crystal grows, the smaller is its stature. If the water evaporates rapidly, the crystals are smaller, because so many crystals are started which do not have material for large growth. When the water is evaporated, to appreciate the beauty of the crystals we should look at them with a lens or microscope. Each crystal is a beautiful little cube, often with a pyramid-shaped depression in each face or side. After the pupils have seen these crystals, the story of where salt is found should be told them.

Salt is obtained by two methods: by mining large deposits of rock salt, and by evaporating water containing a strong solution of salt. The oldest salt works in this country are in Syracuse, New York, where the salt comes from salt springs which were famous among the American Indians. At Ithaca, N. Y., the salt deposits are about 2000 feet below the surface of the earth. Water is forced down into the stratum of rock, which was evidently once the bottom of a briny sea; the water dissolves the salt, and it is then pumped up to the surface and evaporated, leaving the salt in crystals. In Michigan and Louisiana there are other large salt works of a similar character. The largest salt mines in the world are those in Poland, which have been used for hundreds of years. In these mines there are fifty miles of corridors, and the salt has been carved into beautiful chambers with statues and other decorations, all cut from the solid salt. One of these chambers represents a chapel beautifully ornamented.

When the United States was first settled, salt was brought over from England; but this was so expensive that people could not afford it and they soon began to make their own salt by evaporating sea water in kettles on the beach. In those countries where it is scarce, salt is said to be literally worth its weight in gold. The necessity for salt to preserve the health of both people and animals has tempted the governments of some countries to place a special tax upon it; in Italy, especially, the poor people suffer greatly on account of the high price of salt from this cause.

Salt lakes are found in natural basins of arid lands, and are always without outlets. The water which runs in escapes by evaporation, but the salt it brings cannot escape, and accumulates. A salt lick is a place where salt is found on the surface of the earth, usually near a salt spring. Animals will travel a long distance to visit a salt lick which gained its name through their attentions.

LESSON CCXII

SALT

Leading thought-Salt dissolves in water, and as the water evaporates the salt appears in beautiful crystals.

Method-Let each pupil, if possible, have a cup and saucer, a square of paper small enough to go into the saucer, some salt and water. Let each pupil take five teaspoonfuls of water and add to this two spoonfuls of salt, stirring the mixture until dissolved. When the water will take no more salt let each pupil write his name and the date on the square of paper, lay it in the saucer, pressing it down beneath the surface. Let some place their saucers in a warm place, others where they may be kept cool, and others in a draft. If it is impossible for each pupil to have a saucer, two or three pupils may be selected to perform the experiments.

Observations-I. When you pour the salt into the water, what becomes of it? How do you know when the water will hold no more salt?

2. After a saucer, filled with the salt water, stands exposed to the air for several days, what becomes of the water? From which saucers did the water evaporate fastest-those in the warm places, or those in the cold? In which did the crystals form first?

3. Which saucers contained the largest crystals-those from which the water evaporated first, or those from which it evaporated more slowly?

4. Could you see how the crystals began? What is the shape of the perfect salt crystal? Do the smallest crystals have the same shape as the largest ones?

5. What happens to people who cannot get salt to eat?

6. How is dairy salt and table salt obtained? What is rock salt? What are salt licks? Where are the salt mines found? Why is the ocean called "the briny deep?"

7. Name and locate the salt lakes. Why are lakes salt?

LESSON CCXIII

HOW TO STUDY MINERALS

Many children are naturally interested in stones. I once knew two children, aged seven and five, who could invariably select the boulders and pebbles of metamorphic rock in the region about Ithaca. They also could tell, when the pebbles were broken, which parts were quartz and which mica. They had incidentally asked about one of these stones, and I had told them the story of the glacial period and how these stones were torn away from the mountains in Canada and brought down by ice and dropped in Ithaca. It was a story they liked, and their interest in these granite voyagers was always a delightful element of our walks in the field.

A snow crystal. Photomicrograph by W. A. Bentley.

For the pupils in the elementary grades it seems best to limit the study of minerals to those which make up our granite and common rocks. In order to teach about these minerals well, the teacher should have at least one set of labelled specimens. Such a collection may be obtained from Edward E. Howell, 612 17th St., N. W., Washington, D. C., and also from