For the sake of air, as it appeared, or perhaps for that of ready exit in case of some new emergency arising, he took his seat,--not on the sofa, where Miss Keeldar offered him enthronization, nor yet near the fireside, to which Caroline, by a friendly sign, gently invited him, but on a chair close to the door. 
Perhaps to allow an easy exit, he took his seat on a chair close to the door. 