is where the inhabitants of two townships which lie contiguous to each other have usually intercommoned with one another, the beasts of the one straying mutually into the other’s fields, without any molestation from either. This is, indeed, only a permissive right, intended to excuse what, in strictness, is a trespass in both, and to prevent a multiplicity of suits, and therefore either township may inclose and bar out the other, though they have intercommoned time out of mind. 2 Bl. Comm. 33; Co. litt. 122a