Before the magnet was discovered men did not dare to sail very far out on the sea. Whenever they sailed out of sight of land, then they could judge only by the sun and the stars where they were going. But if it was stormy, and the sun and stars were hid, then they had no way of telling where their course lay; and the vessel would drift before the wind, and be dashed on the rocks and go to pieces.
Until the discovery of the magnet they did not sail on the ocean far from land; but after it was discovered, then they made use of the magnetic needle balanced on the point so as to turn freely. By means of this needle they could tell in which direction they were sailing. With the magnetic needle they began to make long voyages far from land, and afterward they discovered many new countries.
There is always on board ship a magnetic needle, called the compass, and they have a measuring-line with knots, at the stern of the ship. And the cord is so constructed that it uncoils and tells how fast the vessel is sailing.
Thus it is that, when they sail a ship, they always know where they are at any given time, and whether they are far from land, and in what direction they are going.
Chapter II
HUMIDITY
WHY does the spider sometimes make a closely spun web and sit in the very center of its nest, and why does it sometimes come out of its nest and spin a new web ?
The spider makes its web according as the weather is at the time, and as it is going to be. By examining its web one can predict what the weather will be; if the spider hides itself away deep down in its nest and does not come out, it means rain. If it emerges from its nest and spins new threads, it means that it will be fine.
How can the spider tell in advance what the weather will be ?
Its sensibilities are so delicate that as soon as the atmosphere begins to have greater humidity, even though this humidity is not perceptible to us, and to us the weather is still clear, the spider perceives that rain is coming. Just as a man feels the dampness when he is undressed, but does not feel it when he is dressed, so the rain is perceptible to the spider when for us it is only preparing to rain.
Why is it that in winter doors swell and refuse to shut, but in summer they dry up and shrink ?
Because in autumn and winter the wood absorbs moisture like a sponge, and swells; but in summer the water evaporates and the wood shrinks.
Why does a soft wood like poplar swell more than oak, for example ?
Because in the hard wood, in the oak, there are less empty spaces, and less room for the water to sink in; while in the soft wood, in the poplar, there are more empty spaces and more room for the water. In decay-ing wood there is still more room and therefore decayed wood swells more than any other kind and sinks sooner.
Beehives are made of the softest wood or of rotten wood; the best hives are made of rotten willow. Why ? Because the air penetrates the rotten stump, and bees like the air in this kind of a hive.
Why do boards warp ?
Because they dry unevenly. If you put a damp board into an oven, the water exudes from one side, and the board gets dry on that side and makes the other side yield to it. It is impossible to shrink the damp side be-cause there is water in it and the whole board bends.
In order to keep floors from warping, they cut out pieces of dry wood and plunge them into boiling water. When the water has been wholly boiled away the pieces are glued together and will not warp, and this kind of inlaid floor is called parket.
Chapter III
DIFFERENT DEGREES OF COHERENCE
WHY is it that the bolsters under a wagon are made of oak while the naves of the wheels are turned out of birch ?
It is necessary to have the bolsters and naves strong, but oak is not more expensive than birch. It is because oak splits lengthwise, while birch* is not easily split, but is made of tough filaments.
Accordingly, though oak has a closer texture than birch, it is so constituted that it splits, while birch is not easily split.
Why are the rims of the wheels and the bounds bent from oak or elm, but never out of birch or linden ?
Because oak and elm, when soaked and softened, become elastic and do not break, while birch and linden splinter on all sides.
All this is due to the fact that the coherence of Parti-cles in oak and birch wood differs in degree.
Chapter IV
CRYSTALS
IF salt is stirred up in water the Particles of the salt are diffused through it and become invisible, but if more and more salt is added then at last the salt ceases to dissolve, and, however much you stir it, the salt remains like a white powder at the bottom. The water had dis-solved the salt to the point of saturation and could take no more. But if the water be heated it will dissolve more; and the salt which refused to melt in the cold water will dissolve away. But if still more salt be added, then not even boiling water will dissolve it. Now, if you still continue to boil the water, the water itself will evaporate in the form of steam, and the salt will be left.
So it is of everything which water dissolves : the water has a limit beyond which it cease* to dissolve sub-stances. Everything is more readily dissolved by hot water than by cold water; but, nevertheless, when the hot water is saturated, it ceases to dissolve any more. The substance remains unchanged but the water may pass off as steam.
If powdered saltpeter is dissolved in water and then more saltpeter is added, and if the whole is heated and allowed to cool without being stirred, then the super-fluous saltpeter will not settle on the bottom in the form of a powder, but will form in clustering hexagonal prisms on the bottom and on the sides. If powdered saltpeter is dissolved in water and then put in a warm place, then the water will evaporate and the residuum of saltpeter will be precipitated in the form of hexagonal crystals.
If common salt is dissolved in water and the water is heated and allowed to evaporate, then the residuum of salt is precipitated also, not in the form of a powder, but in cubes. If saltpeter and salt are dissolved to-gether, the residuum of the two substances do not com-bine, but each is precipitated in its own form : the salt-peter in prisms, the salt in cubes.
If lime or any other salt or any other substance is dissolved in water and the water is evaporated, each substance is precipitated in its own peculiar way : one in triangular prisms, another in octagonal, another in brick-like forms, another in stars each in its own way. These figures are different in all solid substances. Sometimes they are large and are found like stones in the ground; sometimes they are so small that they are invisible to the naked eye; but still each substance has its own form.
If, when water is saturated with saltpeter and the figures begin to form, the edges of the figure are broken with a needle, then again in the same place there will be deposited new atoms of the saltpeter, and the broken edge will be repaired just exactly in its own proper form in hexagonal prisms. It is the same with salt and with everything else. All the infinitesimal atoms move and take their places where they are needed.
When water becomes ice, the same phenomenon takes place. A snowflake comes flying down; no figure can be seen in it. But as soon as it lights on anything moist and cold, on a pane of glass, or on fur, its form may be discerned. You can see a little star or a little plate. On the window-panes the vapor does not freeze at haphazard, but as soon as it begins to freeze it instantly branches out into star shapes.
What is ice ? It is cold solid water. When water turns from a liquid to a solid it forms figures and liberates heat. The same thing takes place with salt-peter when it changes from a liquid to a solid form : heat is liberated. The same with salt, the same with cast-iron, when it cools down from its melted to its solid form.
When anything turns from a liquid to a solid, it liberates heat and begins to form crystals. But when it changes from a solid to a liquid then it absorbs heat; its coldness disappears and its crystals melt.
Take melted iron and let it cool; take hot dough and let it cool; take slaked lime and let it cool heat is pro-duced. Take ice and melt it cold is produced. Take saltpeter, salt, or anything else which is soluble, and put it into water cold is produced. So that when you want to make ice-cream, you melt salt and water.
Chapter V
BAD AIR
ONE festive day, at the village of Nikolskoye, the people had gone to mass.
