When hounds follow an animal's trail, they never run on the track itself, but to one side, about twenty paces from it. When an inexperienced hunter wants to show the dog the scent, and sticks its nose on the track, it will always jump to one side. The track itself smells so strong to the dog that it cannot make out on the track whether the animal has run ahead or backward. It runs to one side, and then only discovers in what direction the scent grows stronger, and so follows the animal. The dog does precisely what we do when somebody speaks very loud in our ears; we step a distance away, and only then do we make out what is being said. Or, if anything we are looking at is too close, we step back and only then make it out. Dogs recognize each other and make signs to each other by means of their scent. The scent is more delicate still in insects. A bee flies directly to the flower that it wants to reach; a worm crawls to its leaf; a bedbug, a flea, a mosquito scents a man a hundred thousand of its steps away. If the particles which separate from a substance and enter our noses are small, how small must be those particles that reach the organ of smell of the insects! TOUCH AND SIGHT Twist the forefinger over the middle finger and touch a small ball with them, so that it may roll between the two fingers, and shut your eyes. You will think that there are two balls. Open your eyes,--and you will see that it is one ball. The fingers have deceived you, but the eyes correct you. Look (best of all sidewise) at a good, clean mirror,--you will think that it is a window or a door, and that there is something behind it. Touch it with a finger,--and you will see that it is a mirror. The eyes have deceived you, but the fingers correct you. THE SILKWORM I had some old mulberry-trees in my garden. My grandfather had planted them. In the fall I was given a dram of silkworm eggs, and was advised to hatch them and raise silkworms. These eggs are dark gray and so small that in that dram I counted 5,835 of them. They are smaller than the tiniest pin-head. They are quite dead; only when you crush them do they crack. The eggs had been lying around on my table, and I had almost forgotten about them. One day, in the spring, I went into the orchard and noticed the buds swelling on the mulberry-trees, and where the sun beat down, the leaves were out. I thought of the silkworm eggs, and took them apart at home and gave them more room. The majority of the eggs were no longer dark gray, as before, but some were light gray, while others were lighter still, with a milky shade. The next morning, I looked at the eggs, and saw that some of the worms had hatched out, while other eggs were quite swollen. Evidently they felt in their shells that their food was ripening.