An exchange suggests, on this . ant topic, that there are thrcc methods which flll the billi First, the old , Frenohplaa. This is followed, chiefly , in PariB, by men who make it a special ' business. They take a deep tub, with water on the bottom and a little elevation in the middle like an island, on which is only a placo for just ono rat to sit. The tub is covered, but ] bas iu the center a trap. This trap is covered, and has a largo balanoe-valvo opening downward. On tlio middle of this valve a piece of ; fried pork or cheese is placed, and when the rat walks on to get the cheese the ■ valve goes down, drops the rat into the water, and moves back in position. A road is made from the rat-hole to the top of the tub by means of pieces of bonrd rabbed with cheese, so as to make the walk more attractive for the rats. In the course of the night some ten, twenty or even more rats may go down, and if the island was not there they woiild bc fonnd most all alive in the morning, quietly swimming arovmd ; but the provisión of the little island savea the trouble of killing them, because tlieir instinct of self-preservation causes them to fight for the exclusive possession of the island, on which in the morning the strongest rat is found in solitary possossion. all the others being killed and drowncd arouud him. Second, tho New York plan, invented by j one of the Friends. The floor neiir the rat-hole is covered with a thin layer of a most caustic potassa. When the rats walk on this it makes their feet sore ; these they lick with their tongues, which make their mouths sore, and the result is that tbey shun the locality, not alone, but appear to teil all the rats in the neighborhoodnbout it, and eveniually the house is entirely abandoDed by them notwithstanding the houRes around are full of rats. Third, the Dutch method. This is said to be used successfully in Holland. A number of rats are left to themselves in a very large trap or cage, with no food whatever. Their craving hunger will cause them to fight, and the weakest will be eaten by the strongest. After a short time the fight is renewed and the next weakest is the victim, and so it goes on until one strong rat is left. When this one has eaten the last remains of the others it is set loóse. The animal has now acquired such a taste for rat flesh that i he is the terror of all ratdom, going about seeking what rat he may devour. In an incredibly short time the premises are abandoned by all other rats, which will not coraè back before the cannibnl rat has left or died.