There are many varieties of this large family; some, like the rattlesnake, cannot climb or swim, but crawl along the ground, the terror of unwary travellers who may tread upon them in the dim forest-paths; others are Water-snakes; some, like the Boa and Python, are dreaded, although not venomous, because, of their enormous strength, and power of crushing their victims in their close embrace; others, like the Cobra, for their deadly bite; while many--we might almost say most--snakes are quite harmless, for it has been reckoned that not more than one in ten is venomous; and none but the giants of this family are dangerous, except for their poisoned bite. The skin of serpents is covered with what are called false scales, which do not overlap each other like those of the fishes, but only seem to do so; and these scales are said to help them to move along rapidly. Most of them are beautifully marked and spotted, and some shine like gold in the sun, while others have pale, soft tints; but these lovely colours fade in death, just as those of fish do; so that a snake in all its glittering beauty can only be seen when alive. They often change their skins, creeping out of the old and appearing ready-dressed in the new. A traveller along the banks of the Nile has often found these cast-off skins in the fields; they are always turned inside out, for the old skin, which is very soft, folds back as the snake slips out of it. [Illustration: SPOTTED SNAKES] I suppose the first thought of all of us, on finding a snake in the grass, would be, Is it a venomous one? So I think you will like to know that poisonous snakes are rare in Europe; and Mr. Wood [Footnote: _Natural History_ p. 521.] tells us that the Viper, which is our only venomous serpent, is one of those least dangerous to life, although far from a friend to those who shrink from pain. It may be known by dark spots down the back. When we speak of venomous serpents, we mean those whose bite is to be dreaded, because it conveys a tiny drop of poison, which mingles with the blood, and often causes intense anguish, ending in death. In poisonous serpents, the venom lies in a little bag at the root of a long sharp tooth, pierced by a narrow tunnel, through which, at the moment when the bite is given, the poison flows into the wound. If these poison-fangs--one on each side--are taken out, the bite of the most dangerous serpents becomes harmless.