The Magic Scorpion.
Place on the surface of the water in a glass or basin a number of small pieces of camphor of various sizes, together representing the form of some animal, say a scorpion. After a little while the scorpion will begin to stir in the water; you will see him move his claws, as though trying to swim, and curl his tail convulsively, as if in pain.
This amusing experiment is easy to perform, and costs practically nothing, for camphor is to be found in every household; but in spite of its simplicity we may deduce from it, as you will see, several interesting observations.
1. Our scorpion floats on the water, but lies almost entirely below the surface. This proves to us that the specific gravity of camphor is nearly, but not quite, equal to that of water.
2. The animal does not dissolve. Camphor is therefore insoluble in water.
3. The different fragments of which our scorpion consists do not separate, but remain one against the other as we originally placed them. This is because they are held together by the force known as cohesion.
4. Lastly, the eccentric movements we have mentioned depend on a well-ascertained but mysterious property of camphor, viz., that when placed on the surface of the water, it moves spontaneously. It is a well-known fact that a morsel of camphor placed in a glass of water will, after a few moments, begin to move either with a sidelong or rotary movement; such movement being due, according to some authorities, to the recoil produced by an escape of liberated gases; according to others, to a mysterious force inherent in the surface of liquids, and known as superficial tension.